| 51. |
- Head, Ashley R., et al.
(author)
-
In situ characterization of the deposition of anatase TiO2 on rutile TiO2(110)
- 2018
-
In: Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 36:2
-
Journal article (peer-reviewed)abstract
- Growing additional TiO2 thin films on TiO2 supstrates in ultrahigh vacuum (UHV)-compatible chambers have many applications for sample preparation, such as smoothing surface morphologies, templating, and covering impurities. However, there has been little study into how to control the morphology of TiO2 films deposited onto TiO2 supstrates, especially using atomic layer deposition (ALD) precursors. Here, the authors show the growth of a TiO2 film on a rutile TiO2(110) surface using titanium tetraisopropoxide (TTIP) and water as the precursors at pressures well below those used in common ALD reactors. X-ray absorption spectroscopy suggests that the relatively low sample temperature (175 °C) results in an anatase film despite the rutile template of the supstrate. Using ambient pressure x-ray photoelectron spectroscopy, the adsorption of TTIP was found to be self-limiting, even at room temperature. No molecular water was found to adsorb on the surface. The deposited thickness suggests that an alternate chemical vapor deposition growth mechanism may be dominating the growth process. This study highlights the possibility that metal oxide film deposition from molecular precursors is an option for sample preparations in common UHV-compatible chambers.
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| 52. |
- Hellgren, Niklas, et al.
(author)
-
X-ray photoelectron spectroscopy analysis of TiBx (1.3 <= x <= 3.0) thin films
- 2021
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 39:2
-
Journal article (peer-reviewed)abstract
- We report on a comprehensive analysis of titanium boride thin films by x-ray photoelectron spectroscopy (XPS). Films were grown by both direct current magnetron sputtering and high- power impulse magnetron sputtering from a compound TiB2 target in Ar discharge. By varying the deposition parameters, the film composition could be tuned over the wide range 1:3 &B/Ti &3:0, as determined by elastic recoil detection analysis and Rutherford backscattering spectrometry. By comparing spectra over this wide range of compositions, we can draw original conclusions about how to interpret XPS spectra of TiBx. By careful spectra deconvolution, the signals from Ti-Ti and B-B bonds can be resolved from those corresponding to stoichiometric TiB2. The intensities of the off-stoichiometric signals can be directly related to the B/Ti ratio of the films. Furthermore, we demonstrate a way to obtain consistent and quantum-mechanically accurate peak deconvolution of the whole Ti 2p envelope, including the plasmons, for both oxidized and sputter-cleaned samples. Due to preferential sputtering of Ti over B, the film B/Ti ratio is best determined without sputter etching of the sample surface. This allows accurate compositional determination, assuming that extensive levels of oxygen are not present in the sample. Fully dense films can be accurately quantified for at least a year after deposition, while underdense samples do not give reliable data if the O/Ti ratio on the unsputtered surface is *3:5. Titanium suboxides detected after sputter etching is further indicative of oxygen penetrating the sample, and quantification by XPS should not be trusted.
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| 53. |
- Honnali, Sanath Kumar, et al.
(author)
-
Effect of tilted closed-field magnetron design on the microstructure and mechanical properties of TiZrNbTaN coatings
- 2023
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 41:4
-
Journal article (peer-reviewed)abstract
- A common design of sputtering systems is to integrate many magnetron sources in a tilted closed-field configuration, which can drastically affect the magnetic field in the chamber and thus plasma characteristics. To study this effect explicitly, multicomponent TiZrNbTaN coatings were deposited at room temperature using direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) with different substrate biases. The coatings were characterized by x-ray diffraction, scanning electron microscopy, nano-indentation, and energy dispersive x-ray spectroscopy. Magnetic field simulations revealed ten times higher magnetic field strengths at the substrate in single-magnetron configuration when compared to the closed-field. As a result, the substrate ion current increased similar to 3 and 1.8 times for DCMS and HiPIMS, respectively. The film microstructure changed with the discharge type, in that DCMS coatings showed large sized columnar structures and HiPIMS coatings show globular nanosized structures with (111) orientation with a closed-field design. Coatings deposited from a single source showed dense columnar structures irrespective of the discharge type and developed (200) orientation only with HiPIMS. Coatings deposited with closed-field design by DCMS had low stress (0.8 to -1 GPa) and hardness in the range from 13 to 18 GPa. Use of HiPIMS resulted in higher stress (-3.6 to -4.3 GPa) and hardness (26-29 GPa). For coatings deposited with single source by DCMS, the stress (-0.15 to -3.7 GPa) and hardness were higher (18-26 GPa) than for coatings grown in the closed-field design. With HiPIMS and single source, the stress was in the range of -2.3 to -4.2 GPa with a similar to 6% drop in the hardness (24-27 GPa).
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| 54. |
- Hsu, Chih-Wei, et al.
(author)
-
Homogeneous high In content InxGa1-x N films by supercycle atomic layer deposition
- 2022
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 40:6
-
Journal article (other academic/artistic)abstract
- InxGa1-x N is a strategically important material for electronic devices given its tunable bandgap, modulated by the In/Ga ratio. However, current applications are hindered by defects caused by strain relaxation and phase separation in the material. Here, we demonstrate growth of homogeneous InxGa1-x N films with 0.3 < x < 0.8 up to similar to 30 nm using atomic layer deposition (ALD) with a supercycle approach, switching between InN and GaN deposition. The composition is uniform along and across the films, without signs of In segregation. The InxGa1-x N films show higher In-content than the value predicted by the supercycle model. A more pronounced reduction of GPC(InN) than GPC(GaN) during the growth processes of InN and GaN bilayers is concluded based on our analysis. The intermixing between InN and GaN bilayers is suggested to explain the enhanced overall In-content. Our results show the advantage of ALD to prepare high-quality InxGa1-x N films, particularly with high In-content, which is difficult to achieve with other growth methods.
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| 55. |
- Huang, Jing-Jia, et al.
(author)
-
Conformal and superconformal chemical vapor deposition of silicon carbide coatings
- 2022
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 40:5
-
Journal article (peer-reviewed)abstract
- The approaches to conformal and superconformal deposition developed by Abelson and Girolami for a low-temperature, low-pressure chemical vapor deposition (CVD) setting relevant for electronic materials in micrometer or submicrometer scale vias and trenches, are tested here in a high-temperature, moderate pressure CVD setting relevant for hard coatings in millimeter-scale trenches. Conformal and superconformal deposition of polycrystalline silicon carbide (SiC) can be accomplished at deposition temperatures between 950 and 1000 degrees C with precursor partial pressure higher than 20 Pa and an optional minor addition of HCl as a growth inhibitor. The conformal deposition at low temperatures is ascribed to slower kinetics of the precursor consumption along the trench depth, whereas the impact of high precursor partial pressure and addition of inhibitor is attributable to surface site blocking. With the slower kinetics and the site blocking from precursor saturation leading the growth to nearly conformal and the possibly preferential inhibition effect near the opening than at the depth, a superconformal SiC coating with 2.6 times higher thickness at the bottom compared to the top of a 1 mm trench was achieved. Published under an exclusive license by the AVS.
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| 56. |
- Huang, Jing-Jia, et al.
(author)
-
Superconformal silicon carbide coatings via precursor pulsed chemical vapor deposition
- 2023
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 41:3
-
Journal article (peer-reviewed)abstract
- In this work, silicon carbide (SiC) coatings were successfully grown by pulsed chemical vapor deposition (CVD). The precursors silicon tetrachloride (SiCl4) and ethylene (C2H4) were not supplied in a continuous flow but were pulsed alternately into the growth chamber with H-2 as a carrier and a purge gas. A typical pulsed CVD cycle was SiCl4 pulse-H-2 purge-C2H4 pulse-H-2 purge. This led to growth of superconformal SiC coatings, which could not be obtained under similar process conditions using a constant flow CVD process. We propose a two-step framework for SiC growth via pulsed CVD. During the SiCl4 pulse, a layer of Si is deposited. In the following C2H4 pulse, this Si layer is carburized, and SiC is formed. The high chlorine surface coverage after the SiCl4 pulse is believed to enable superconformal growth via a growth inhibition effect.
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| 57. |
- Hägglund, Carl, 1975-, et al.
(author)
-
Growth, intermixing, and surface phase formation for zinc tin oxide nanolaminates produced by atomic layer deposition
- 2016
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 34:2
-
Journal article (peer-reviewed)abstract
- A broad and expanding range of materials can be produced by atomic layer deposition at relatively low temperatures, including both oxides and metals. For many applications of interest, however, it is desirable to grow more tailored and complex materials such as semiconductors with a certain doping, mixed oxides, and metallic alloys. How well such mixed materials can be accomplished with ALD requires knowledge of the conditions under which the resulting films will be mixed, solid solutions, or laminated. The growth and lamination of zinc oxide and tin oxide is studied here by means of the extremely surface sensitive technique of low energy ion scattering, combined with bulk composition and thickness determination, and X-ray diffraction. At the low temperatures used for deposition (150 °C) there is little evidence for atomic scale mixing even with the smallest possible bilayer period, and instead a morphology with small ZnO inclusions in a SnOx matrix is deduced. Post-annealing of such laminates above 400 °C however produces a stable surface phase with a 30% increased density. From the surface stoichiometry, this is likely the inverted spinel of zinc stannate, Zn2SnO4. Annealing to 800 °C results in films containing crystalline Zn2SnO4, or multilayered films of crystalline ZnO, Zn2SnO4 and SnO2 phases, depending on the bilayer period.
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| 58. |
- Hänninen, Tuomas, et al.
(author)
-
Silicon oxynitride films deposited by reactive high power impulse magnetron sputtering using nitrous oxide as a single-source precursor
- 2015
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 33:5, s. 05E121-
-
Journal article (peer-reviewed)abstract
- Silicon oxynitride thin films were synthesized by reactive high power impulse magnetron sputtering of silicon in argon/nitrous oxide plasmas. Nitrous oxide was employed as a single-source precursor supplying oxygen and nitrogen for the film growth. The films were characterized by elastic recoil detection analysis, x-ray photoelectron spectroscopy, x-ray diffraction, x-ray reflectivity, scanning electron microscopy, and spectroscopic ellipsometry. Results show that the films are silicon rich, amorphous, and exhibit a random chemical bonding structure. The optical properties with the refractive index and the extinction coefficient correlate with the film elemental composition, showing decreasing values with increasing film oxygen and nitrogen content. The total percentage of oxygen and nitrogen in the films is controlled by adjusting the gas flow ratio in the deposition processes. Furthermore, it is shown that the film oxygen-to-nitrogen ratio can be tailored by the high power impulse magnetron sputtering-specific parameters pulse frequency and energy per pulse. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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| 59. |
- Högberg, Hans, et al.
(author)
-
Reactive sputtering of delta-ZrH2 thin films by high power impulse magnetron sputtering and direct current magnetron sputtering
- 2014
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 32:4, s. 041510-
-
Journal article (peer-reviewed)abstract
- Reactive sputtering by high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) of a Zr target in Ar/H-2 plasmas was employed to deposit Zr-H films on Si(100) substrates, and with H content up to 61 at.% and O contents typically below 0.2 at.% as determined by elastic recoil detection analysis. X-ray photoelectron spectroscopy reveals a chemical shift of similar to 0.7 eV to higher binding energies for the Zr-H films compared to pure Zr films, consistent with a charge transfer from Zr to H in a zirconium hydride. X-ray diffraction shows that the films are single-phase delta-ZrH2 (CaF2 type structure) at H content greater thansimilar to 55 at.% and pole figure measurements give a 111 preferred orientation for these films. Scanning electron microscopy cross-section images show a glasslike microstructure for the HiPIMS films, while the DCMS films are columnar. Nanoindentation yield hardness values of 5.5-7 GPa for the delta-ZrH2 films that is slightly harder than the similar to 5 GPa determined for Zr films and with coefficients of friction in the range of 0.12-0.18 to compare with the range of 0.4-0.6 obtained for Zr films. Wear resistance testing show that phase-pure delta-ZrH2 films deposited by HiPIMS exhibit up to 50 times lower wear rate compared to those containing a secondary Zr phase. Four-point probe measurements give resistivity values in the range of similar to 100-120 mu Omega cm for the delta-ZrH2 films, which is slightly higher compared to Zr films with values in the range 70-80 mu Omega cm.
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| 60. |
- Jamnig, Andreas, et al.
(author)
-
Manipulation of thin metal film morphology on weakly interacting substrates via selective deployment of alloying species
- 2022
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 40:3
-
Journal article (peer-reviewed)abstract
- We demonstrate a versatile concept for manipulating morphology of thin (& LE;25 nm) noble-metal films on weakly interacting substrates using growth of Ag on SiO2 as a model system. The concept entails deployment of minority metallic (Cu, Au, Al, Ti, Cr, and Mo) alloying species at the Ag-layer growth front. Data from in situ and real-time monitoring of the deposition process show that all alloying agents-when deployed together with Ag vapor throughout the entire film deposition-favor two-dimensional (2D) growth morphology as compared to pure Ag film growth. This is manifested by an increase in the substrate area coverage for a given amount of deposited material in discontinuous layers and a decrease of the thickness at which a continuous layer is formed, though at the expense of a larger electrical resistivity. Based on ex situ microstructural analyses, we conclude that 2D morphological evolution under the presence of alloying species is predominantly caused by a decrease of the rate of island coalescence completion during the initial film-formation stages. Guided by this realization, alloying species are released with high temporal precision to selectively target growth stages before and after coalescence completion. Pre-coalescence deployment of all alloying agents yields a more pronounced 2D growth morphology, which for the case of Cu, Al, and Au is achieved without compromising the Ag-layer electrical conductivity. A more complex behavior is observed when alloying atoms are deposited during the post-coalescence growth stages: Cu, Au, Al, and Cr favor 2D morphology, while Ti and Mo yield a more pronounced three-dimensional morphological evolution. The overall results presented herein show that targeted deployment of alloying agents constitutes a generic platform for designing bespoken heterostructures between metal layers and technologically relevant weakly interacting substrates.& nbsp;Published under an exclusive license by the AVS.
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| 61. |
- Johansson, Leif I, et al.
(author)
-
Li induced effects in the core level and pi-band electronic structure of graphene grown on C-face SiC
- 2015
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 33:6
-
Journal article (peer-reviewed)abstract
- Studies of the effects induced in the electronic structure after Li deposition, and subsequent heating, on graphene samples prepared on C-face SiC are reported. The as prepared graphene samples are essentially undoped, but after Li deposition, the Dirac point shifts down to 1.2 eV below the Fermi level due to electron doping. The shape of the C 1s level also indicates a doping concentration of around 10(14) cm(-2) after Li deposition, when compared with recent calculated results of core level spectra of graphene. The C 1s, Si 2p, and Li 1s core level results show little intercalation directly after deposition but that most of the Li has intercalated after heating at 280 degrees C. Heating at higher temperatures leads to desorption of Li from the sample, and at 1030 degrees C, Li can no longer be detected on the sample. The single pi-band observable from multilayer C-face graphene samples in conventional angle resolved photoelectron spectroscopy is reasonably sharp both on the initially prepared sample and after Li deposition. After heating at 280 degrees C, the p-band appears more diffuse and possibly split. The Dirac point becomes located at 0.4 eV below the Fermi level, which indicates occurrence of a significant reduction in the electron doping concentration. Constant energy photoelectron distribution patterns extracted from the as prepared graphene C-face sample and also after Li deposition and heating at 280 degrees C look very similar to earlier calculated distribution patterns for monolayer graphene. (C) 2015 Author(s).
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| 62. |
- Junaid, Muhammad, et al.
(author)
-
Structural, mechanical, and magnetic properties of GaFe3N thin films
- 2016
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 34:4
-
Journal article (peer-reviewed)abstract
- Using the density-functional theory, the structural, mechanical, and magnetic properties were investigated for different GaFe3N configurations: ferromagnetic, ferrimagnetic, paramagnetic, and nonmagnetic. Ferrimagnetic and high-spin ferromagnetic states exhibit the lowest energy and are the competing ground states as the total energy difference is 0.3 meV/atom only. All theoretically predicted values could be fully confirmed by experiments. For this, the authors synthesized phase pure, homogeneous, and continuous GaFe3N films by combinatorial reactive direct current magnetron sputtering. Despite the low melting point of gallium, the authors succeeded in the growth of GaFe3N films at a temperature of 500 degrees C. Those thin films exhibit a lattice parameter of 3.794 angstrom and an elastic modulus of 226620 GPa. Magnetic susceptibility measurements evidence a magnetic phase transitions at 8.060.1 K. The nearly saturated magnetic moment at 65 T is about 1.6 mu B/Fe and is close to the theoretically determined magnetic moment for a ferrimagnetic ordering (1.72 lB/Fe).
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| 63. |
- Karslloǧlu, Osman, et al.
(author)
-
Prospects for the expansion of standing wave ambient pressure photoemission spectroscopy to reactions at elevated temperatures
- 2022
-
In: Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 40:1
-
Journal article (peer-reviewed)abstract
- Standing wave ambient pressure photoemission spectroscopy (SWAPPS) is a promising method to investigate chemical and potential gradients across solid-vapor and solid-liquid interfaces under close-to-realistic environmental conditions, far away from high vacuum. Until now, these investigations have been performed only near room temperature, but for a wide range of interfacial processes, chief among them being heterogeneous catalysis, measurements at elevated temperatures are required. One concern in these investigations is the temperature stability of the multilayer mirrors, which generate the standing wave field. At elevated temperatures, degradation of the multilayer mirror due to, for example, interdiffusion between the adjacent layers, decreases the modulation of the standing wave field, thus rendering SWAPPS experiments much harder to perform. Here, we show that multilayer mirrors consisting of alternate B4C and W layers are stable at temperatures exceeding 600 °C and are, thus, promising candidates for future studies of surface and subsurface species in heterogeneous catalytic reactions using SWAPPS.
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| 64. |
- Kateb, Movaffaq, et al.
(author)
-
Effect of substrate bias on microstructure of epitaxial film grown by HiPIMS : An atomistic simulation
- 2020
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 38:4
-
Journal article (peer-reviewed)abstract
- The authors explore the combination of high power impulse magnetron sputtering (HiPIMS) and substrate bias for the epitaxial growth of the Cu film on the Cu (111) substrate by molecular dynamics simulation. A fully ionized deposition flux was used to represent the high ionization fraction in the HiPIMS process. To mimic different substrate bias, the authors assumed the deposition flux with a flat energy distribution in the low, moderate, and high energy ranges. The authors also compared the results of the fully ionized flux with results assuming a completely neutral flux, in analogy with thermal evaporation. It is confirmed that in the low energy regime, HiPIMS presents a slightly smoother surface and more interface mixing compared to that of thermal evaporation. In the moderate energy HiPIMS, however, an atomically smooth surface was obtained with a slight increase in the interface mixing compared to low energy HiPIMS. In the high energy regime, HiPIMS presents severe interface mixing with a smooth surface but limited growth due to resputtering from the surface. The results also indicate that fewer crystal defects appear in the film for moderate energy HiPIMS. The authors attribute this behavior to the repetition frequency of collision events. In particular, the high energy HiPIMS suffers from high repetition of collision events that does not allow the reconstruction of the film. While in the low energy HiPIMS, there are not enough events to overcome the island growth. At moderate energy, collision events repeat in a manner that provides enough time for reconstruction, which results in a smooth surface, fewer defects, and limited intermixing.
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| 65. |
- Kateb, Movaffaq, et al.
(author)
-
Role of ionization fraction on the surface roughness, density, and interface mixing of the films deposited by thermal evaporation, dc magnetron sputtering, and HiPIMS : An atomistic simulation
- 2019
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : AVS Science and Technology Society. - 0734-2101 .- 1520-8559. ; 37:3
-
Journal article (peer-reviewed)abstract
- The effect of ionization fraction on the epitaxial growth of Cu film on Cu (111) substrate at room temperature is explored. Three deposition methods, thermal evaporation, dc magnetron sputtering (dcMS), and high power impulse magnetron sputtering (HiPIMS) are compared. Three deposition conditions, i.e., fully neutral, 50% ionized, and 100% ionized flux were considered thermal evaporation, dcMS, and HiPIMS, respectively, for similar to 20 000 adatoms. It is shown that higher ionization fraction of the deposition flux leads to smoother surfaces by two major mechanisms, i.e., decreasing clustering in the vapor phase and bicollision of high energy ions at the film surface. The bicollision event consists of local amorphization which fills the gaps between islands followed by crystallization due to secondary collisions. The bicollision events are found to be very important to prevent island growth to become dominant and increase the surface roughness. Regardless of the deposition method, epitaxial Cu thin films suffer from stacking fault areas (twin boundaries) in agreement with recent experimental results. Thermal evaporation and dcMS deposition present negligible interface mixing while HiPIMS deposition presents considerable interface mixing. Published by the AVS.
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| 66. |
- Kauppinen, Christoffer, et al.
(author)
-
Atomic layer etching of gallium nitride (0001)
- 2017
-
In: Journal of Vacuum Science and Technology A. - : American Vacuum Society. - 0734-2101. ; 35:6
-
Journal article (peer-reviewed)abstract
- In this work, atomic layer etching (ALE) of thin film Ga-polar GaN(0001) is reported in detail using sequential surface modification by Cl2 adsorption and removal of the modified surface layer by low energy Ar plasma exposure in a standard reactive ion etching system. The feasibility and reproducibility of the process are demonstrated by patterning GaN(0001) films by the ALE process using photoresist as an etch mask. The demonstrated ALE is deemed to be useful for the fabrication of nanoscale structures and high electron mobility transistors and expected to be adoptable for ALE of other materials.
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| 67. |
- Kindlund, Hanna, et al.
(author)
-
Effect of WN content on toughness enhancement in V1–xWxN/MgO(001) thin films
- 2014
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - Linköping : Linköping University Electronic Press. - 0734-2101 .- 1520-8559. ; 32:3, s. 030603-
-
Journal article (peer-reviewed)abstract
- The authors report the growth and mechanical properties of epitaxial B1 NaCl-structure V1-xWxN/MgO(001) thin films with 0 ≤ x ≤ 0.60. The Gibbs free energy of mixing, calculated using density functional theory (DFT), reveals that cubic V1-xWxN solid solutions with 0 ≤ x ≤ 0.7 are stable against spinodal decomposition and separation into the equilibrium cubic-VN and hexagonal-WN binary phases. The authors show experimentally that alloying VN with WN leads to a monotonic increase in relaxed lattice parameters, enhanced nanoindentation hardnesses, and reduced elastic moduli. Calculated V1-xWxN lattice parameters and elastic moduli (obtained from calculated C11, C12, and C44 elastic constants) are in good agreement with experimental results. The observed increase in alloy hardness, with a corresponding decrease in the elastic modulus at higher x values, combined with DFT-calculated decreases in shear to bulk moduli ratios, and increased Cauchy pressures (C12–C44) with increasing x reveal a trend toward increased toughness.
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| 68. |
- Kindlund, Hanna, et al.
(author)
-
Epitaxial V0.6W0.4N/MgO(001): Evidence for ordering on the cation sublattice
- 2013
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 31:4
-
Journal article (peer-reviewed)abstract
- V0.6W0.4N alloys are grown on MgO(001) by ultrahigh vacuum reactive magnetron sputtering from V and W targets in 10 mTorr pure-N-2 atmospheres at temperatures T-s ranging from 600 to 900 degrees C. Based on x-ray diffraction and transmission electron microscopy results, all films have the B1-NaCl crystal structure and grow with a cube-on-cube epitaxial relationship to the substrate, (001)(VWN)parallel to(001)(MgO) and [100](VWN parallel to)[100](MgO). Rutherford backscattering spectrometry analyses show that the N content in V0.6W0.4Nx alloys decreases with increasing T-s from overstoichiometric with x = 1.13 at 600 degrees C, to approximately stoichiometric with x = 1.08 at 700 degrees C, to understoichiometric at 800 degrees C (x = 0.80) and 900 degrees C (x = 0.75). High-resolution scanning transmission electron microscopy, Z-contrast, and selected-area electron diffraction investigations of V0.6W0.4N(001) alloys grown at 600 and 700 degrees C reveal the onset of W ordering on adjacent 111 planes of the metal sublattice; no ordering is observed for understoichiometric films grown at higher temperatures.
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| 69. |
- Kindlund, Hanna, et al.
(author)
-
Growth and mechanical properties of 111-oriented V0.5Mo0.5Nx/Al2O3(0001) thin films
- 2018
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 36:5
-
Journal article (peer-reviewed)abstract
- Pseudobinary V0.5Mo0.5Nx(111) alloys with the Bl-NaCl crystal structure are grown on Al2O3(0001) substrates in an ultra-high-vacuum system by reactive magnetron sputter deposition in mixed Ar/N-2 atmospheres at temperatures T-s between 100 and 900 degrees C. Nitrogen-to-metal, N/(V + Mo), fractions x vary monotonically from 0.9 +/- 0.1 with T-s = 100 degrees C to 0.4 +/- 0.1 at T-s = 900 degrees C. Nitrogen loss at higher growth temperatures leads to a corresponding decrease in the relaxed lattice parameter a(o) from 4.21 +/- 0.01 angstrom at T-s = 300 degrees C to 4.125 +/- 0.005 angstrom with T-s = 900 degrees C. Scanning electron micrographs of cube-corner nanoindents extending into the substrate show that the films are relatively ductile, exhibiting material pile-up (plastic flow) around the indent edges. Nanoindentation hardnesses H and elastic moduli E, obtained using a calibrated Berkovich tip, of V0.5Mo0.5Nx(111) layers increase with increasing T-s(decreasing x) from 15 +/- 1 and 198 +/- 5 GPa at 100 degrees C to 23 +/- 2 and 381 +/- 11 GPa at 900 degrees C. These values are lower than the corresponding results obtained for the 001-oriented V0.5Mo0.5Nx films In addition, film wear resistance increases with increasing T-s, while the coefficient of friction, under 1000 mu N loads, is 0.09 +/- 0.01 for all layers. Published by the AVS.
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| 70. |
- Kubart, Tomas, 1977-, et al.
(author)
-
High power impulse magnetron sputtering of diamond-like carbon coatings
- 2020
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 38:4
-
Journal article (peer-reviewed)abstract
- High power impulse magnetron sputtering (HiPIMS) of diamond-like carbon coatings is reviewed. Three variations of HiPIMS were used to deposit diamond-like carbon coatings: use of neon as compared to argon for sputtering, very high discharge peak current density in an Ar atmosphere, and the use of bursts of short sputtering pulses. All three variations were able to provide sufficient ion-to-neutral ratios to effectively control the coating quality using substrate bias. The resulting coatings are typically smooth, amorphous, hard (up to 25 GPa), and dense but have low stress (below 2.5 GPa). The coatings exhibit an increased stability at higher temperature (up to 500 °C) compared to the coatings prepared using standard magnetron sputtering. The resulting coatings also exhibited low wear rates in ambient ball-on-disc tests (2.1 × 10−8 mm3 N−1 m−1). These improvements are explained in terms of the rate of sputtered carbon atom ionization in the plasma and material transport to the substrate. However, the chemical bonding in the films is not yet well understood as relatively low sp3 bond content has been observed.
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| 71. |
- Landälv, Ludvig, 1982-, et al.
(author)
-
Influence of Si doping and O-2 flow on arc-deposited (Al,Cr)(2)O-3 coatings
- 2019
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 37:6
-
Journal article (peer-reviewed)abstract
- (Al,Cr)(2)O-3 coatings with Al/( Al + Cr) = 0.5 or Al = 70 at. %, doped with 0, 5, or 10 at. % Si, were deposited on hard metal and Si(100) substrates to elucidate the influence of Si on the resulting coatings. The chemical analysis of the coatings showed between 3.3 and 7.4 at. % metal fraction Si incorporated into all studied coatings depending on cathode Si composition. The incorporated Si content does not change significantly with different oxygen flows covering a wide range of deposition conditions from low to high O-2 flow during growth. The addition of Si promotes the metastable B1-like cubic structure over the thermodynamically stable corundum structure. The hardness determined by nanoindentation of the as-deposited coatings is slightly reduced upon Si incorporation as well as upon increased Al content. Si is found enriched in droplets but can also be found at a lower content, evenly spread, without visible segregation at the similar to 5 nm scale, in the actual oxide coating. The positive effect of improved cathode erosion upon Si incorporation has to be balanced against the promotion of the metastable B1-like structure, having lower room temperature hardness and inferior thermal stability compared to the corundum structure. Published by the AVS.
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| 72. |
- Larsson, Fredrik, et al.
(author)
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Atomic layer deposition of amorphous tin-gallium oxide films
- 2019
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 37:3
-
Journal article (peer-reviewed)abstract
- A wide range of applications benefit from transparent semiconducting oxides with tunable electronic properties, for example, electron transport layers in solar cell devices, where the electron affinity is a key parameter. Presently, a few different ternary oxides are used for this purpose, but the attainable electron affinity range is typically limited. In this study, the authors develop a low-temperature atomic layer deposition (ALD) process to grow amorphous Sn1-xGaxOy thin films from dimethylamino-metal complexes and water. This oxide is predicted to provide a wide selection of possible electron affinity values, from around 3 eV for pure Ga2O3 to 4.5 eV for pure SnO2. The ALD process is evaluated for deposition temperatures in the range of 105-195 degrees C by in situ quartz crystal microbalance and with ex situ film characterization. The growth exhibits an ideal-like behavior at 175 degrees C, where the film composition can be predicted by a simple rule of mixture. Depending on film composition, the growth per cycle varies in the range of 0.6-0.8 angstrom at this temperature. Furthermore, the film composition for a given process appears insensitive to the deposition temperature. From material characterization, it is shown that the deposited films are highly resistive, fully amorphous, and homogeneous, with moderate levels of impurities (carbon, nitrogen, and hydrogen). By tailoring the metal cation ratio in films grown at 175 degrees C, the optical bandgap can be varied in the range from 2.7 eV for SnO2 to above 4.2 eV for Ga2O3. The bandgap also varies significantly as a function of deposition temperature. This control of properties indicates that Sn1-xGaxOy is a promising candidate for an electron transport layer material in a wide electron affinity range. Published by the AVS.
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| 73. |
- Le Febvrier, Arnaud, et al.
(author)
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Wet-cleaning of MgO(001): Modification of surface chemistry and effects on thin film growth investigated by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy
- 2017
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 35:2
-
Journal article (peer-reviewed)abstract
- The effect of the wet-cleaning process using solvents and detergent on the surface chemistry of MgO(001) substrate for film deposition was investigated. Six different wet-cleaning processes using solvent and detergent were compared. The effect on film growth was studied by the example system ScN. The surface chemistry of the cleaned surface was studied by x-ray photoelectron spectroscopy and the film/substrate interface after film growth was investigated by time-of-flight secondary ion mass spectroscopy. The surface composition is dependent on the wet-cleaning process. Sonication in a detergent before the solvents yield a pure oxide surface compared to hydroxide/carbonate contaminated surface for all the other processes. An annealing step is efficient for the removal of carbon contamination as well as most of the hydroxide or carbonates. The study of the film/substrate interface revealed that the wet-cleaning process significantly affects the final interface and film quality. The substrate cleaned with detergent followed by solvent cleaning exhibited the cleanest surface of the substrate before annealing, after annealing, in addition to the sharpest film/substrate interface. (C) 2017 American Vacuum Society.
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| 74. |
- Lee, Wei Chuang, et al.
(author)
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Monolayer calibration of endofullerenes with x-ray absorption from implanted keV ion doses
- 2024
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 42:2
-
Journal article (peer-reviewed)abstract
- X-ray absorption spectroscopy (XAS) has the highest sensitivity for chemical element detection on surfaces. With this approach, small amounts of lanthanide-containing endofullerene molecules (Ho3N@C80) have been measured by total electron yield at a low flux bending magnet beamline. The monolayer coverage is calibrated by extrapolating the signals of constant doses (3 x 1014 cm-2) of Ho ions implanted into SiO2 with energies between 2 and 115 keV. At room temperature, the Ho XAS spectra of the molecules and implanted ions indicate trivalent but not identical Ho ground states. Still, this approach demonstrates a way for calibration of small coverages of molecules containing open core-shell elements.
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| 75. |
- Li, Xiao, et al.
(author)
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Determining role of W+ ions in the densification of TiAlWN thin films grown by hybrid HiPIMS/DCMS technique with no external heating
- 2023
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 41:1
-
Journal article (peer-reviewed)abstract
- Hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) with substrate bias synchronized to the high mass metal-ion fluxes was previously proposed as a solution to reduce energy consumption during physical vapor deposition processing and enable coatings on temperature-sensitive substrates. In this approach, no substrate heating is used (substrate temperature is lower than 150 C-o) and the thermally activated adatom mobility, necessary to grow dense films, is substituted by overlapping collision cascades induced by heavy ion bombardment and consisting predominantly of low-energy recoils. Here, we present direct evidence for the crucial role of W+ ion irradiation in the densification of Ti0.31Al0.60W0.09N films grown by the hybrid W-HiPIMS/TiAl-DCMS co-sputtering. The peak target current density J(max) on the W target is varied from 0.06 to 0.78 A/cm(2) resulting in more than fivefold increase in the number of W+ ions per deposited metal atom, eta = W+/(W + Al + Ti) determined by time-resolved ion mass spectrometry analyses performed at the substrate plane under conditions identical to those during film growth. The DCMS is adjusted appropriately to maintain the W content in the films constant at Ti0.31Al0.60W0.09N. The degree of porosity, assessed qualitatively from cross-sectional SEM images and quantitatively from oxygen concentration profiles as well as nanoindentation hardness, is a strong function of eta ( J m a x ). Layers grown with low eta values are porous and soft, while those deposited under conditions of high eta are dense and hard. Nanoindentation hardness of Ti0.31Al0.60W0.09N films with the highest density is & SIM;33 GPa, which is very similar to values reported for layers deposited at much higher temperatures (420-500 C-o) by conventional metal-ion-based techniques. These results prove that the hybrid HiPIMS/DCMS co-sputtering with bias pulses synchronized to high mass metal ion irradiation can be successfully used to replace conventional solutions. The large energy losses associated with heating of the entire vacuum chamber are avoided, by focusing the energy input to where it is in fact needed, i.e., the workpiece to be coated.
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| 76. |
- Lindahl, Erik, et al.
(author)
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In situ study of nickel formation during decomposition of chemical vapor deposition Ni3N films
- 2010
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 28:5, s. 1203-1209
-
Journal article (peer-reviewed)abstract
- The thermal decomposition of Ni3N thin films, deposited by chemical vapor deposition on SrTiO3 (001) and Si (100) substrates, has been studied by in situ x-ray diffraction, as well as temperature-programed controlled gas emission in both inert and hydrogen atmospheres. The decomposition at inert atmosphere conditions starts at the film/substrate interface, which results in a high degree of ordering in the formed nickel film. In the H-2 atmosphere, the initial film ordering is less pronounced and the decomposition occurs from the film surface and downward. This means that by choosing the annealing atmosphere, inert or hydrogen, the formation of the Ni film can be localized to either the original nitride/substrate interface or to the surface of the nitride. The annealed films show a cube-on-cube growth with respect to the SrTiO3 (001) substrate. The film morphology after the annealing experiments resembles the one of the as-deposited films. The lowest resistivity value is measured for the films annealed in the H-2 atmosphere. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3478298]
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| 77. |
- Lundin, Daniel, et al.
(author)
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Influence of pulse power amplitude on plasma properties and film deposition in high power pulsed plasma enhanced chemical vapor deposition
- 2014
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 32:3
-
Journal article (peer-reviewed)abstract
- The discharge characteristics in high power pulsed plasma enhanced chemical vapor deposition is studied with the aim to characterize the impact of high power pulses (HiPP). Using a power scheme of combined HiPP and direct current (DC) to ignite the plasma discharge, and adjusting the HiPP/DC time-averaged power ratio while keeping the total power constant, the effect of the high power pulses was isolated from the total power. By monitoring the discharge current along with the optical emission from the plasma, it is found that the amount of available ions increased with increasing HiPP/DC ratio, which indicates a higher plasma density. Using carbon films deposited from acetylene in an argon plasma as model system, a strong increase in deposition rate with higher HiPP/DC is observed. The increased deposition rate is ascribed to a more efficient plasma chemistry generated by the denser plasma.
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| 78. |
- Magnus, Fridrik, et al.
(author)
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Current-voltage-time characteristics of the reactive Ar/O2 high power impulse magnetron sputtering discharge
- 2012
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 30:5
-
Journal article (peer-reviewed)abstract
- The discharge current–voltage–time waveforms are studied in the reactive Ar/O2 high power impulse magnetron sputtering discharge with a titanium target for 400 μs long pulses. The discharge current waveform is highly dependent on both the pulse repetition frequency and discharge voltage and the current increases with decreasing frequency or voltage. The authors attribute this to an increase in the secondary electron emission yield during the self-sputtering phase of the pulse, as an oxide forms on the target.
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| 79. |
- Magnuson, Martin, 1965-, et al.
(author)
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Compositional dependence of epitaxial Tin+1SiCn MAX-phase thin films grown from a Ti3SiC2 compound target
- 2019
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 37:2
-
Journal article (peer-reviewed)abstract
- The authors investigate sputtering of a Ti3SiC2 compound target at temperatures ranging from RT (no applied external heating) to 970 °C as well as the influence of the sputtering power at 850 °C for the deposition of Ti3SiC2 films on Al2O3(0001) substrates. Elemental composition obtained from time-of-flight energy elastic recoil detection analysis shows an excess of carbon in all films, which is explained by differences in the angular distribution between C, Si, and Ti, where C scatters the least during sputtering. The oxygen content is 2.6 at. % in the film deposited at RT and decreases with increasing deposition temperature, showing that higher temperatures favor high purity films. Chemical bonding analysis by x-ray photoelectron spectroscopy shows C–Ti and Si–C bonding in the Ti3SiC2 films and Si–Si bonding in the Ti3SiC2 compound target. X-ray diffraction reveals that the phases Ti3SiC2, Ti4SiC3, and Ti7Si2C5 can be deposited from a Ti3SiC2 compound target at substrate temperatures above 850 °C and with the growth of TiC and the Nowotny phase Ti5Si3Cx at lower temperatures. High-resolution scanning transmission electron microscopy shows epitaxial growth of Ti3SiC2, Ti4SiC3, and Ti7Si2C5 on TiC at 970 °C. Four-point probe resistivity measurements give values in the range ∼120 to ∼450 μΩ cm and with the lowest values obtained for films containing Ti3SiC2, Ti4SiC3, and Ti7Si2C5.
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| 80. |
- Malinovskis, Paulius, et al.
(author)
-
Synthesis and characterization of MoB2-x thin films grown by nonreactive DC magnetron sputtering
- 2016
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 34, s. 031511-1-031511-8
-
Journal article (peer-reviewed)abstract
- DC magnetron sputtering was used to depositmolybdenumboridethin films for potential low-friction applications. The films exhibit a nanocomposite structure with ∼10 nm large MoB2−x (x > 0.4) grains surrounded by a boron-rich tissue phase. The preferred formation of the metastable and substoichiometric hP3-MoB2structure (AlB2-type) is explained with kinetic constraints to form the thermodynamically stable hR18-MoB2 phase with a very complex crystal structure. Nanoindentation revealed a relatively high hardness of (29 ± 2) GPa, which is higher than bulk samples. The high hardness can be explained by a hardening effect associated with the nanocomposite microstructure where the surrounding tissue phase restricts dislocation movement. A tribological study confirmed a significant formation of a tribofilm consisting of molybdenum oxide and boron oxide, however, without any lubricating effects at room temperature.
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| 81. |
- Marchack, Nathan, et al.
(author)
-
In-situ etch rate study of HfxLayOz in Cl-2/BCl3 plasmas using the quartz crystal microbalance
- 2015
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 33:3
-
Journal article (peer-reviewed)abstract
- The etch rate of HfxLayOz films in Cl-2/BCl3 plasmas was measured in-situ in an inductively coupled plasma reactor using a quartz crystal microbalance and corroborated by cross-sectional SEM measurements. The etch rate depended on the ion energy as well as the plasma chemistry. In contrast to other Hf-based ternary oxides, the etch rate of HfxLayOz films was higher in Cl-2 than in BCl3. In the etching of Hf0.25La0.12O0.63, Hf appeared to be preferentially removed in Cl-2 plasmas, per surface compositional analysis by x-ray photoelectron spectroscopy and the detection of HfCl3 generation in mass spectroscopy. These findings were consistent with the higher etch rate of Hf0.25La0.12O0.63 than that of La2O3.
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| 82. |
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| 83. |
- Mattsson, Andreas, et al.
(author)
-
Infrared spectroscopy study of adsorption and photodecomposition of formic acid on reduced and defective rutile TiO2 (110) surfaces
- 2014
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 32:6
-
Journal article (peer-reviewed)abstract
- Adsorption and photodecomposition of formic acid on rutile TiO2 (110) have been investigated with infrared reflection–absorption spectroscopy (IRRAS) employing p- and s-polarized light along the [001] and [ 11⎯⎯0 ] crystal directions. The single crystal surfaces were prepared either by sputtering and annealing in ultrahigh vacuum (UHV) to obtain a reduced surface (r-TiO2), or by sputtering without annealing to create a rough, highly defective surface (sp-TiO2). Results are compared with corresponding measurements on rutile nanocrystals performed in synthetic air. IRRAS spectra obtained on r-TiO2 and rutile nanocrystals are very similar, and show that in both cases formic acid dissociates and is predominately adsorbed as a bridging bidentate formate species, and that the formate adsorption structure on the nanocrystals is dominated by interactions with majority (110) surfaces. In contrast, the IRRAS spectra on sp-TiO2 are different, with only minor spectral features associated with (110) surfaces and lost azimuthal symmetry, both of which imply changed adsorption geometry due to bonding to low-coordinated Ti atoms with lower valences. The UV-induced rate of formate photodecomposition is about 30 times higher on rutile nanocrystals in synthetic air compared with sp-TiO2 under UHV conditions, and even larger than on r-TiO2. These differences are explained by the lack of oxygen and limited hydroxyl coverage under UHV conditions. The difference in reactivity between the r-TiO2 and sp-TiO2 surfaces is attributed to a high concentration of strongly bonded bridging bidentate formate species on the (110) surface, which lowers its reactivity. The results point to a pressure gap where the availability of molecular oxygen and the hydroxyl concentration limit the photoreactivity in UHV leading to an almost 20-fold decrease of the formate degradation rate in UHV. In contrast, the structure represented by the single crystal (110) surface is shown to capture the essential structural properties, which dictates the formic acid adsorption and adsorption structure of rutile nanocrystals.
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| 84. |
- Mei, A B, et al.
(author)
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Physical properties of epitaxial ZrN/MgO(001) layers grown by reactive magnetron sputtering
- 2013
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 31:6, s. 061516-
-
Journal article (peer-reviewed)abstract
- Single-crystal ZrN films, 830 nm thick, are grown on MgO(001) at 450 degrees C by magnetically unbalanced reactive magnetron sputtering. The combination of high-resolution x-ray diffraction reciprocal lattice maps, high-resolution cross-sectional transmission electron microscopy, and selected-area electron diffraction shows that ZrN grows epitaxially on MgO(001) with a cube-on-cube orientational relationship, (001)(ZrN)parallel to(001)(MgO) and [100](ZrN)parallel to[100](MgO). The layers are essentially fully relaxed with a lattice parameter of 0.4575 nm, in good agreement with reported results for bulk ZrN crystals. X-ray reflectivity results reveal that the films are completely dense with smooth surfaces (roughness = 1.3 nm, consistent with atomic-force microscopy analyses). Based on temperature-dependent electronic transport measurements, epitaxial ZrN/MgO(001) layers have a room-temperature resistivity rho(300K) of 12.0 mu Omega-cm, a temperature coefficient of resistivity between 100 and 300K of 5.6 x 10(-8) Omega-cm K-1, a residual resistivity rho(o) below 30K of 0.78 mu Omega-cm (corresponding to a residual resistivity ratio rho(300K)/rho(15K) = 15), and the layers exhibit a superconducting transition temperature of 10.4 K. The relatively high residual resistivity ratio, combined with long in-plane and out-of-plane x-ray coherence lengths, xi(parallel to) = 18 nm and xi(perpendicular to) = 161 nm, indicates high crystalline quality with low mosaicity. The reflectance of ZrN(001), as determined by variable-angle spectroscopic ellipsometry, decreases slowly from 95% at 1 eV to 90% at 2 eV with a reflectance edge at 3.04 eV. Interband transitions dominate the dielectric response above 2 eV. The ZrN(001) nanoindentation hardness and modulus are 22.7 +/- 1.7 and 450 +/- 25 GPa.
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| 85. |
- Mikula, Marian, et al.
(author)
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Experimental and computational studies on toughness enhancement in Ti-Al-Ta-N quaternaries
- 2017
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 35:6
-
Journal article (peer-reviewed)abstract
- Design of hard ceramic material coatings with enhanced toughness, which prevents crack formation/propagation leading to brittle failure during application, is a primary industrial requirement. In this work, experimental methods supported by ab initio density functional theory (DFT) calculations and electronic structure analyses are used to investigate the mechanical behavior of magnetron sputtered Ti-Al-Ta-N hard coatings. The as-deposited Ti1-x-yAlxTayN (y = 0-0.60) films exhibit a single phase cubic sodium chloride (B1) structure identified as TiAl(Ta)N solid solutions. While the hardness H of Ti0.46Al0.54N (32.5 +/- 2 GPa) is not significantly affected by alloying with TaN (H of the quaternary nitrides varies between 26 +/- 2 and 35 +/- 4 GPa), the elastic stiffness monotonically decreases from 442 to 354 GPa with increasing Ta contents, which indicates improved toughness in TiAlTaN. Consistent with the experimental findings, the DFT results show that Ta substitutions in TiAlN reduce the shear resistance due to the enhanced occupation of metal-metal bonding states while preserving strong metal-N bonds. The metal-N bonding character, however, is progressively modified from prevalently ionic (TiAlN) toward more covalent (TiAlTaN). (C) 2017 American Vacuum Society.
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| 86. |
- Moreira, Milena A., et al.
(author)
-
Deposition of highly textured AlN thin films by reactive high power impulse magnetron sputtering
- 2015
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 33:2
-
Journal article (peer-reviewed)abstract
- Aluminum nitride thin films were deposited by reactive high power impulse magnetron sputtering (HiPIMS) and pulsed direct-current on Si (100) and textured Mo substrates, where the same deposition conditions were used for both techniques. The films were characterized by x-ray diffraction and atomic force microscopy. The results show a pronounced improvement in the AlN crystalline texture for all films deposited by HiPIMS on Si. Already at room temperature, the HiPIMS films exhibited a strong preferred (002) orientation and at 400 degrees C, no contributions from other orientations were detected. Despite the low film thickness of only 200 nm, an x-scan full width at half maximum value of 5.1 degrees was achieved on Si. The results are attributed to the high ionization of sputtered material achieved in HiPIMS. On textured Mo, there was no significant difference between the deposition techniques.
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| 87. |
- Müller, Martina, et al.
(author)
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Hard x-ray photoelectron spectroscopy of tunable oxide interfaces
- 2022
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 40:1
-
Journal article (peer-reviewed)abstract
- The tunability of the oxygen content in complex oxides and heterostructures has emerged as a key to designing their physical functionalities. Controlling the interface reactivity by redox reactions provides a powerful means to deliberately set distinct oxide phases and emerging properties. We present routes on how to control oxygen-driven redox mechanisms in ultrathin ferro(i)magnetic and ferroelectric oxide films and across oxide interfaces. We address the growth and control of metastable EuO oxide phases, the control of phase transitions of binary Fe oxides by oxygen migration, the in operando determination of NiFe2O4/SrTiO3 interface band alignments, as well as the role of interfacial oxide exchange in ferroelectric HfO 2-based capacitors-uncovered by the unique capabilities of photoelectron spectroscopy and, in particular, using hard x-rays.
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| 88. |
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| 89. |
- Mårtensson, Nils, 1949-, et al.
(author)
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Uppsala and Berkeley : Two essential laboratories in the development of modern photoelectron spectroscopy
- 2022
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 40:4
-
Journal article (peer-reviewed)abstract
- The development of modern photoelectron spectroscopy is reviewed with a special focus on the importance of research at Uppsala University and at Berkeley. The influence of two pioneers, Kai Siegbahn and Dave Shirley, is underlined. Early interaction between the two centers helped to kick-start the field. Both laboratories have continued to play an important role in the field, both in terms of creating new experimental capabilities and developing the theoretical understanding of the spectroscopic processes. (C)2022 Author(s).
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| 90. |
- Nadhom, Hama, et al.
(author)
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Area selective deposition of iron films using temperature sensitive masking materials and plasma electrons as reducing agents
- 2021
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 39:4
-
Journal article (peer-reviewed)abstract
- The potential of area-selective deposition (ASD) with a newly developed chemical vapor deposition (CVD) method, which utilizes plasma electrons as reducing agents for deposition of metal-containing films, is demonstrated using temperature sensitive polymer-based masking materials. The masking materials tested were polydimethylsiloxane, polymethylmethacrylate, polystyrene, parafilm, Kapton tape, Scotch tape, and office paper. The masking materials were all shown to prevent film growth on the masked area of the substrate without being affected by the film deposition process. X-ray photoelectron spectroscopy analysis confirms that the films deposited consist mainly of iron, whereas no film material is found on the masked areas after mask removal. Scanning electron microscopy analysis of films deposited with nonadhesive masking materials show that film growth extended for a small distance underneath the masking material, indicating that the CVD process with plasma electrons as reducing agents is not a line-of-sight deposition technique. The reported methodology introduces an inexpensive and straightforward approach for ASD that opens for exciting new possibilities for robust and less complex area-selective metal-on-metal deposition.
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| 91. |
- Nadhom, Hama, et al.
(author)
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Chemical vapor deposition of metallic films using plasma electrons as reducing agents
- 2020
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 38:3
-
Journal article (peer-reviewed)abstract
- Metallic thin films are key components in electronic devices and catalytic applications. Deposition of a conformal metallic thin film requires using volatile precursor molecules in a chemical vapor deposition (CVD) process. The metal centers in such molecules typically have a positive valence, meaning that reduction of the metal centers is required on the film surface. Powerful molecular reducing agents for electropositive metals are scarce and hamper the exploration of CVD of electropositive metals. The authors present a new CVD method for depositing metallic films where free electrons in a plasma discharge are utilized to reduce the metal centers of chemisorbed precursor molecules. They demonstrate this method by depositing Fe, Co, and Ni from their corresponding metallocenes using electrons from an argon plasma as a reducing agent.
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| 92. |
- Nedfors, Nils, et al.
(author)
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Effect of synchronized bias in the deposition of TiB2 thin films using high power impulse magnetron sputtering
- 2018
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 36:3
-
Journal article (peer-reviewed)abstract
- Titanium diboride thin films have been deposited from a compound TiB2 target on Si(001) substrates at a temperature of 500 degrees C using high power impulse magnetron sputtering (HiPIMS) at a frequency of 1000 Hz and pulse lengths of 20 and 40 mu s. A -60V bias pulse of different pulse length was applied at different time delay relative to the HiPIMS pulse. The average energy per deposited species, amp;lt; E-D amp;gt; = E-i(J(i)/J(t)), where E-i is the average ion energy and J(i)/J(t) is the ratio of the ion bombarding flux to the total flux of deposited species, is strongly dependent on bias mode. A change in preferred orientation from (101) to (001) is observed when amp;lt; E-D amp;gt; increase above 50 eV. The limited adatom mobility at amp;lt; E-D amp;gt; below 50 eV promote growth of fast growing planes resulting in a (101) texture, while amp;lt; E-D amp;gt; above 50 eV supply sufficient energy for development of the thermodynamically more favorable (001) texture. A linear increase in compressive residual stress with the increase in amp;lt; E-D amp;gt; is also found, due to more intensive Ar+ ion bombardment. Analysis of charge-state-resolved plasma chemistry and ion energy shows that the total flux of bombarding ions contains a higher fraction of B+ when the bias is applied in synchronous with the HiPIMS pulse instead of after, resulting in a lower residual stress at similar values of amp;lt; E-D amp;gt; (cf. -2.0 +/- 0.2 and -2.6 +/- 0.1 GPa). This study shows that use of a bias synchronized in different modes relative to the HiPIMS pulse, can be used as a tool to control amp;lt; E-D amp;gt; and to some extent the type of bombarding species, and hence the microstructure of TiB2 thin films. Published by the AVS.
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| 93. |
- Nedfors, Nils, et al.
(author)
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Nb-B-C thin films for electrical contact applications deposited by magnetron sputtering
- 2014
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 32:4, s. 041503-
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Journal article (peer-reviewed)abstract
- The high wear resistance, high chemical inertness, and high electrical conductivity of magnetron-sputtered transition metal diborides (MeB2) make them a candidate material for sliding electrical contacts. However, their high hardness makes it difficult to penetrate surface oxides, resulting in a high electrical contact resistance. We have in this study investigated how the contact resistance can be improved by the formation of softer Nb-B-C films. The Nb-B-C films were deposited by magnetron sputtering and shown to exhibit a nanocomposite microstructure consisting of nanocrystalline NbB2-x grains with a solid solution of C separated by an amorphous BCx phase. The formation of the BCx phase reduces the hardness from 41 GPa for the NbB2-x film to 19 GPa at 36 at.% C. As a consequence the contact resistance is drastically reduced and the lowest contact resistance of 35 mΩ (contact force 5 N) is achieved for a film containing 30 at.% C. However, crack formation and subsequent delamination and fragmentation is observed for the C-containing Nb-B-C films in tribology tests resulting in high friction values for these films.
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| 94. |
- Niiranen, Pentti, et al.
(author)
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Plasma electron characterization in electron chemical vapor deposition
- 2024
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 42:2
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Journal article (peer-reviewed)abstract
- Recently, a novel approach of depositing metallic films with chemical vapor deposition (CVD), using plasma electrons as reducing agents, has been presented and is herein referred to as e-CVD. By applying a positive substrate bias to the substrate holder, plasma electrons are drawn to the surface of the substrate, where the film growth occurs. In this work, we have characterized the electron flux at the substrate position in terms of energy and number density as well as the plasma potential and floating potential when maintaining an unbiased and a positively biased substrate. The measurements were performed using a modified radio frequency Sobolewski probe to overcome issues due to the coating of conventional electrostatic probes. The plasma was generated using a DC hollow cathode plasma discharge at various discharge powers and operated with and without precursor gas. The results show that the electron density is typically around 10(16) m(-3) and increases with plasma power. With a precursor, an increase in the substrate bias shows a trend of increasing electron density. The electron temperature does not change much without precursor gas and is found in the range of 0.3-1.1 eV. Introducing a precursor gas to the vacuum chamber shows an increase in the electron temperature to a range of 1-5 eV and with a trend of decreasing electron temperature as a function of discharge power. From the values of the plasma potential and the substrate bias potential, we were able to calculate the potential difference between the plasma and the substrate, giving us insight into what charge carriers are expected at the substrate under different process conditions.
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| 95. |
- Nyman, Johan, et al.
(author)
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Composition, structure, and mechanical properties of cathodic arc deposited Cr-rich Cr-N coatings
- 2023
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 41:2
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Journal article (peer-reviewed)abstract
- We arc deposit Cr-rich Cr-N coatings and show that these coatings are a promising alternative to electrodeposited hard chrome. We find that the substrate bias is of importance for controlling the N content in the grown coatings as it determines the degree of preferential resputtering of N. The substrate bias also affects the substrate temperature and film growth rate. Higher bias results in higher temperatures due to higher energy transfer to the substrate, while the growth rate decreases due to an increased re-sputtering. The N content affects the morphology, microstructure, hardness, and resistivity of the coatings. The hardness increases from 10 GPa with 0.5 at. % N to 17 GPa with 7.5 at. % N, after which no further increase in hardness is seen. At the same time, the grain structure changes from columnar to more featureless and the resistivity rises from 15 to 45 mu omega cm.
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| 96. |
- Pedersen, Henrik, et al.
(author)
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Green CVD-Toward a sustainable philosophy for thin film deposition by chemical vapor deposition
- 2021
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 39:5
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Journal article (peer-reviewed)abstract
- Thin films of materials are critical components for most areas of sustainable technologies, making thin film techniques, such as chemical vapor deposition (CVD), instrumental for a sustainable future. It is, therefore, of great importance to critically consider the sustainability aspects of CVD processes themselves used to make thin films for sustainable technologies. Here, we point to several common practices in CVD that are not sustainable. From these, we offer a perspective on several principles for a sustainable, "Green CVD" philosophy, which we hope will spur research on how to make CVD more sustainable without affecting the properties of the deposited film. We hope that these principles can be developed by the research community over time and be used to establish research on how to make CVD more sustainable and that a Green CVD philosophy can develop new research directions for both precursor and reactor design to reduce the precursor and energy consumption in CVD processes.
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| 97. |
- Pedersen, Henrik, et al.
(author)
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On the change of preferential growth orientation in chemical vapor deposition of titanium carbide by aromatic hydrocarbon precursors
- 2013
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 31:2
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Journal article (peer-reviewed)abstract
- Thin films of titanium carbide grown by chemical vapor deposition exhibit a strong preferential (111) growth direction if aromatic hydrocarbons, such as benzene, are used as a carbon precursor. If aliphatic hydrocarbons such as methane are used, growth on the (100) surface is preferred. In this study, quantum chemical computations are used to study the adsorption of benzene and methane on the (100) and (111) surfaces to provide an explanation for the changed growth behavior. The adsorption energy of benzene is found to be approximately twice as high on the (111) surface as compared to the (100) surface, and adsorption studies further suggest that benzene chemisorbs on the (111) surface, while it physisorbs on the (100) surface. The studies reveal no significant differences in adsorption energy or behavior for methane on the two surfaces. The authors propose that the higher benzene adsorption energy and different adsorption behavior on the (111) surface are the explanations for the preferential growth orientation.
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| 98. |
- Pedersen, Henrik, et al.
(author)
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Thermodynamic stability of hexagonal and rhombohedral boron nitride under chemical vapor deposition conditions from van der Waals corrected first principles calculations
- 2019
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 37:4
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Journal article (peer-reviewed)abstract
- Thin films of boron nitride (BN), particularly the sp(2)-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN), are interesting for several electronic applications, given the bandgaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800K and 1000-10000Pa, respectively. In this letter, the authors use the van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. The authors find that r-BN is the stable sp(2)-hybridized phase at CVD conditions, while h-BN is metastable. Thus, their calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.
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| 99. |
- Persson, Per O A, et al.
(author)
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Exploring the thermal behavior and diffusive functionality of structural defects and phase boundaries in near-stoichiometric chromium diborides by in situ scanning transmission electron microscopy
- 2024
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 42:2
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Journal article (other academic/artistic)abstract
- Near-stoichiometric chromium diboride films were subject to in situ annealing inside a scanning transmission electron microscope to access the thermal behavior of the film and embedded structural planar defects. Independent of films' stoichiometry, the planar defects were unaffected by the applied heat treatments. On the contrary, the interfaces between the boron-rich tissue phase and the CrB2 phase were reshaped in the overstoichometric CrB2 film. At high temperatures, diffusion of contact metal species (platinum) from the focused ion beam sample preparation was triggered, with subsequent migration onto the sample. This resulted in the formation of metal-rich regions as directly observed and characterized at the atomic level. We determined that platinum did not react with the diboride structure but is accommodated by various defects present in the film.
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| 100. |
- Petrov, Ivan, et al.
(author)
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Controlling the boron-to-titanium ratio in magnetron-sputter-deposited TiBx thin films
- 2017
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 35:5
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Journal article (peer-reviewed)abstract
- Magnetron sputter-deposited TiBx films grown from TiB2 targets are typically highly overstoichiometric with x ranging from 3.5 to 2.4 due to differences in Ti and B preferential ejection angles and gasphase scattering during transport between the target and the substrate. The authors show that the use of highly magnetically unbalanced magnetron sputtering leads to selective ionization of sputter-ejected Ti atoms which are steered via an external magnetic field to the film, thus establishing control of the B/Ti ratio with the ability to obtain stoichiometric TiB2 films over a wide range in Ar sputtering pressures. (C) 2017 American Vacuum Society.
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