| 1. |
- Kubart, Tomas, et al.
(författare)
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Modelling of sputtering yield amplification in serial reactive magnetron co-sputtering
- 2012
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 206:24, s. 5055-5059
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Tidskriftsartikel (refereegranskat)abstract
- Serial magnetron co-sputtering can be used to increase the deposition rate in reactive deposition of thin films. The increase in deposition rate is achieved by sputtering yield amplification through doping the sputtering target by a heavy element. The dopant is introduced by means of sputtering from an auxiliary target onto a rotating primary magnetron. During sputtering of the primary target, the dopant is implanted into the target surface. Here we present a model describing the serial co-sputtering technique. The model is based on the binary collision approximation and takes into account the dynamical sputtering and mixing at the target surface. As an example, W and Bi doping in reactive sputter deposition of Al2O3 is analyzed. W is shown to be very efficient dopant which can increase the deposition rate for oxide up to 100% with 1.6 at.% of W in the resulting coating. Doping by Bi is not very effective due to the low surface binding energy of Bi. The simulations show that sputtering yield amplification can be realized in the serial co-sputtering setup with rotating magnetrons.
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| 2. |
- Austgen, M, et al.
(författare)
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Sputter yield amplification by tungsten doping of Al(2)O(3) employing reactive serial co-sputtering : process characteristics and resulting film properties
- 2011
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 44:34, s. 345501-
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Tidskriftsartikel (refereegranskat)abstract
- The deposition rate of reactively sputtered Al(2)O(3) coatings is demonstrated to increase by 80% upon tungsten doping of the used aluminium target. This effect is based on the recoil of the sputtering species at implanted dopants below the target surface and is termed sputter yield amplification. For the investigation of this effect, a novel type of magnetron sputter deposition system is employed that facilitates serial co-sputtering. In this technique doping of the elementary target is enabled by a dynamic sputtering process from an auxiliary cathode. In our case, the rotating aluminium target is dynamically coated with tungsten from this auxiliary cathode. Since the primary target rotates, the auxiliary cathode is placed in series with the primary erosion zone. The deposition rate of Al(2)O(3) can be considerably increased in this process already for very low concentrations of approximately 1% of tungsten in the resulting film. A characterization of the dynamics of reactive sputtering as a function of target rotation speed is performed.
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| 3. |
- Kubart, Tomas, 1977-, et al.
(författare)
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Modelling of sputtering yield amplification effect in reactive deposition of oxides
- 2010
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 204:23, s. 3882-3886
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Tidskriftsartikel (refereegranskat)abstract
- Many reactive sputter deposition applications require high deposition rates. The primary limiting parameters in magnetron sputtering are the target power dissipation and sputtering yields of the target elements. In reactive deposition of oxides, the deposition rate is of particular interest due to the low sputtering yield of most commonly used oxides. Traditional high rate techniques rely on a feedback control of the oxygen partial pressure to prevent formation of oxide on the target and hence enable operation in the transition area. An alternative approach, based on target doping, is presented in this paper.By doping the sputtering target with heavy elements, it is possible to substantially enhance the sputtering yield and hence the deposition rate. Simulations of the partial sputtering yield values for aluminium from doped targets sputtered in reactive atmosphere have been carried out. The Monte Carlo based TRIDYN computer code has been used for simulations. The program has been used to find out optimum alloying conditions to obtain maximum partial sputtering yield for deposition of Al2O3. Our simulations indicate that the sputtering yield amplification in reactive sputtering may lead to much higher relative deposition rate increase than in a nonreactive case. The highest relative increase may be achieved in the transition region but substantial increase is predicted also in the oxide mode.
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| 4. |
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| 5. |
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| 6. |
- Sarakinos, Kostas, et al.
(författare)
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The effect of the backscattered energetic atoms on the stress generation and the surface morphology of reactively sputtered vanadium nitride films
- 2008
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 516:14, s. 4568-4573
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Tidskriftsartikel (refereegranskat)abstract
- During the reactive magnetron sputtering of transition metal nitrides in an Ar-N-2 ambient, Ar+ and N-2(+) plasma ions are neutralized upon impingement on the target and are backscattered towards the growing film as neutral Ar and N species, respectively. Based on simulations, as well as on plasma and on film characterization techniques we manifest the relationship between the bombardment by the backscattered energetic atoms and the properties of reactively sputtered vanadium nitride (VN) films. Depending on the N-2 flow (q(N2)) two bombardment regimes are established. In the first regime, (q(N2) less than 20 seem) the contribution of the N species to the energetic bombardment is insignificant. The major bombarding species in this regime are the backscattered Ar species, as well as positive plasma ions and sputtered atoms. These species have relatively low energies and subplantation ratios and thus, their energy is transferred to the surface of the growing film. In the second regime (q(N2) greater than 20 scent) the backscattered N atoms are the major bombarding species and their flux to the growing film increases with increasing the N-2 flow. We argue that the backscattered N atoms have higher energy and subplantation ratio in comparison to the other bombarding species. As a result, a higher part of their energy is dissipated in the bulk of the film. The two bombarding regimes correlate well with the residual compressive stresses and the surface roughness of the films. Films grown at q(N2)less than20 seem exhibit low compressive stresses and their roughness drops when q(N2) is increased. This consistent with the low subplantation ratio and the transfer of the energy of the bombarding species to surface the growing film. The compressive stresses of films grown at q(N2) greater than 20 seem are higher, than those of the films grown in the first regime, and increase with increasing N-2 flow. This is attributed to the subplantation of the bombarding N species in the growing film.
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| 7. |
- Sarakinos, Kostas, et al.
(författare)
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The role of backscattered energetic atoms in film growth in reactive magnetron sputtering of chromium nitride
- 2007
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Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 40:3, s. 778-785
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Tidskriftsartikel (refereegranskat)abstract
- In this work the impact of backscattered energetic atoms on film growth in reactive sputtering of CrNx (x less than= 1) is manifested. We use film and plasma characterization techniques, as well as simulations in order to study the dynamics of the target-discharge-film interactions. The results show that the primary bombarding species of the growing film are N-2(+) plasma ions, which are neutralized and backscattered by the target in the form of atomic N. It is shown that the backscattered N atoms have energies which are significantly higher than those of other bombarding species, i.e. the backscattered Ar atoms, the sputtered atoms and the plasma ions. Moreover, it is found that CrN films exhibit compressive stresses of 2.6 GPa and a density close to the bulk value. We attribute these properties to the bombardment by backscattered energetic atoms, in particular N. Pure Cr films are also studied for reference.
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| 8. |
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| 9. |
- Alami, J., et al.
(författare)
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On the deposition rate in a high power pulsed magnetron sputtering discharge
- 2006
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 89:15, s. 154104-
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the high pulse current and the duty cycle on the deposition rate in high power pulsed magnetron sputtering (HPPMS) is investigated. Using a Cr target and the same average target current, deposition rates are compared to dc magnetron sputtering (dcMS) rates. It is found that for a peak target current density I-Tpd of up to 570 mA cm(-2), HPPMS and dcMS deposition rates are equal. For I-Tpd greater than 570 mA cm(-2), optical emission spectroscopy shows a pronounced increase of the Cr+/Cr-0 signal ratio. In addition, a loss of deposition rate, which is attributed to self-sputtering, is observed.
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| 10. |
- Alami, J., et al.
(författare)
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On the phase formation of titanium oxide films grown by reactive high power pulsed magnetron sputtering
- 2009
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Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 42:11, s. 115204-
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Tidskriftsartikel (refereegranskat)abstract
- High power pulsed magnetron sputtering is used for the growth of titanium dioxide (TiO(2)) films at different working pressures and orientations of the substrate with respect to the target surface. In the case of substrates oriented parallel to the target surface, the increase in the working pressure from 0.5 to 3 Pa results in the growth of crystalline TiO(2) films with phase compositions ranging from rutile to anatase/rutile mixtures. When depositions are performed on substrates placed perpendicularly to the target surface, rutile films that consist of TiO(2) nanocrystals embedded in an amorphous matrix are obtained at 0.5 Pa. Increase in the working pressure leads to the deposition of amorphous films. These findings are discussed in the light of the energetic bombardment provided to the growing film at the various deposition conditions.
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| 11. |
- Alami, J., et al.
(författare)
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On the relationship between the peak target current and the morphology of chromium nitride thin films deposited by reactive high power pulsed magnetron sputtering
- 2009
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Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 42:1, s. 015304-
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Tidskriftsartikel (refereegranskat)abstract
- High power pulsed magnetron sputtering (HPPMS) is used to deposit CrN films without external heating at different peak target currents, while the average current is kept constant. Films are also grown by dc magnetron sputtering (dcMS), for reference. The plasma properties, the deposition rate and the morphology of the films are investigated. The plasma analysis reveals that HPPMS provides higher fluxes of ionized species (both gas and sputtered) to the growing film, as compared with dcMS. In addition, the ionic bombardment during HPPMS increases, when the peak target current is increased. The HPPMS films exhibit changes of the density and the surface roughness as the peak target current increased, while the deposition rate decreases drastically. Furthermore, it is found that different thin-film morphologies are obtained starting from a porous columnar morphology for the dcMS films, which turns to a dense columnar one at low peak target currents and ends up to a featureless morphology at high peak target currents for the films grown by HPPMS. A new structure zone model specific for high ionization sputtering is, therefore, outlined.
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| 12. |
- Meyer, Tobias, et al.
(författare)
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A compact microscope setup for multimodal nonlinear imaging in clinics and its application to disease diagnostics
- 2013
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Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 138:14, s. 4048-4057
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Tidskriftsartikel (refereegranskat)abstract
- The past years have seen increasing interest in nonlinear optical microscopic imaging approaches for the investigation of diseases due to the method's unique capabilities of deep tissue penetration, 3D sectioning and molecular contrast. Its application in clinical routine diagnostics, however, is hampered by large and costly equipment requiring trained staff and regular maintenance, hence it has not yet matured to a reliable tool for application in clinics. In this contribution implementing a novel compact fiber laser system into a tailored designed laser scanning microscope results in a small footprint easy to use multimodal imaging platform enabling simultaneously highly efficient generation and acquisition of second harmonic generation (SHG), two-photon excited fluorescence (TPEF) as well as coherent anti-Stokes Raman scattering (CARS) signals with optimized CARS contrast for lipid imaging for label-free investigation of tissue samples. The instrument combining a laser source and a microscope features a unique combination of the highest NIR transmission and a fourfold enlarged field of view suited for investigating large tissue specimens. Despite its small size and turnkey operation rendering daily alignment dispensable the system provides the highest flexibility, an imaging speed of 1 megapixel per second and diffraction limited spatial resolution. This is illustrated by imaging samples of squamous cell carcinoma of the head and neck (HNSCC) and an animal model of atherosclerosis allowing for a complete characterization of the tissue composition and morphology, i.e. the tissue's morphochemistry. Highly valuable information for clinical diagnostics, e. g. monitoring the disease progression at the cellular level with molecular specificity, can be retrieved. Future combination with microscopic probes for in vivo imaging or even implementation in endoscopes will allow for in vivo grading of HNSCC and characterization of plaque deposits towards the detection of high risk plaques.
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| 13. |
- Nyberg, Tomas, et al.
(författare)
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State of the art in Reactive Magnetron Sputtering
- 2006
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Ingår i: Invited to The third Mikkeli International Industrial Coating Seminar, MIICS 2006, Mikkeli, Finland, March 16-18, 2006 and Conference Proceedings.
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Konferensbidrag (refereegranskat)
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| 14. |
- Sarakinos, Kostas, et al.
(författare)
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A semi-quantitative model for the deposition rate in non-reactive high power pulsed magnetron sputtering
- 2008
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Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 41:21, s. 215301-
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical treatment of the deposition process in a non-reactive high power pulsed magnetron sputtering discharge is presented. This leads to the development of a semi-quantitative model that describes the deposition rate as a function of process parameters, such as the target voltage, the peak target current density, the pulse frequency and the pulse duty cycle. The effect of these parameters on the deposition rate is studied experimentally using carbon, chromium and copper targets. The implementation of the model on the experimental results enables the estimation of the relative fractions of the sputtering gas ions (Ar(+)) and the sputtered metal ions (M(+)) in the total ion flux at the target. The M(+) content in the target ion current is calculated to adopt values up to similar to 72% and similar to 98% for the chromium and the copper targets, respectively. In contrast, the target ion current is found to consist mostly of Ar(+) species in the case of the carbon target. The significantly higher fractions of M(+) ions for chromium and copper are attributed to their higher ionization probability and their higher sputtering yield in comparison with carbon.
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| 15. |
- Sarakinos, Kostas, et al.
(författare)
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Growth of tio(x) films magnetron sputtering by high power pulsed from a compound tio(1.8) target
- 2007
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Ingår i: REVIEWS ON ADVANCED MATERIALS SCIENCE. - : INST PROBLEMS MECHANICAL ENGINEERING-RUSSIAN ACAD SCIENCES. - 1606-5131. ; 15:1, s. 44-48
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Tidskriftsartikel (refereegranskat)abstract
- High power pulsed magnetron sputtering (HPPMS) has been employed for the growth of TiO(x) (x greater than 1.8) films from a ceramic TiO(1.8) target in an Ar-O(2) ambient. The film properties have been compared to those deposited by dc magnetron sputtering (dcMS). Both HPPMS and dcMS films exhibit an amorphous structure and are transparent. Furthermore, films grown by HPPMS have improved properties, such as higher density, higher refractive index and smoother film surface, as compared to those deposited by dcMS.
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| 16. |
- Sarakinos, Kostas, et al.
(författare)
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Process characteristics and film properties upon growth of TiOx films by high power pulsed magnetron sputtering
- 2007
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Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 40:7, s. 2108-2114
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Tidskriftsartikel (refereegranskat)abstract
- In this work TiOx (x greater than 1.8) films are grown reactively from a ceramic TiO1.8 target employing high power pulsed magnetron sputtering (HPPMS) at a constant average target current. The effect of the pulse on/off time configuration on the target and the discharge characteristics as well as on the film properties is investigated. The target voltage (V-T) increases from 480 to 650V and the peak target current (I-Tp) increases from 2 to 40A when the pulse off-time is increased from 200 to 2450 mu s, while the on-time is kept constant at 50 mu s. This is accompanied by an increase in the number of Ti atoms sputtered from the target, as manifested by time-resolved optical emission spectroscopy (OES) measurements. OES also manifests an increase in the ionization of the sputtered Ti atoms with increasing I-Tp. The above changes in the target and discharge characteristics affect the deposition rate so that the latter increases with increasing I-Tp up to a value of 14 A, above which the deposition rate drops. In all the cases the deposition rates are up to similar to 40% higher compared to the rates achieved for films grown by dc magnetron sputtering (dcMS) which are also studied for reference. The increase in I-Tp from 2 to 40A also affects the films properties. It is shown that a drop in the surface roughness from 1.1 to 0.5 nm takes place. These values are lower than the surface roughness of films grown by dcMS (1.35 nm). Moreover, films grown by HPPMS are found to have higher densities (up to 3.83 g cm(-3)) and higher refractive indices (up to 2.48) in comparison to the films grown by dcMS (3.71 g cm(-3) and 2.38, respectively).
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| 17. |
- Sarakinos, Kostas, et al.
(författare)
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Process stabilization and enhancement of deposition rate during reactive high power pulsed magnetron sputtering of zirconium oxide
- 2008
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 202:20, s. 5033-5035
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Tidskriftsartikel (refereegranskat)abstract
- Reactive high power pulsed magnetron sputtering (HPPMS) of zirconium oxide exhibits a stable and hysteresis-free transition zone, as opposed to reactive direct current magnetron sputtering (dcMS). The stabilization of the transition zone in HPPMS facilitates the growth of transparent zirconium oxide films at lower target coverage, in comparison to dcMS. The lower target coverage, in turn, allows for film deposition rates up to 2 times higher than those achieved by dcMS. The mechanisms which lead to the process stabilization in reactive HPPMS are discussed.
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| 18. |
- Sarakinos, Kostas, et al.
(författare)
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The effect of the microstructure and the surface topography on the electrical properties of thin Ag films deposited by high power pulsed magnetron sputtering
- 2008
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 202:11, s. 2323-2327
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Tidskriftsartikel (refereegranskat)abstract
- In this work thin silver (Ag) films are grown employing high power pulsed magnetron sputtering (HPPMS) for various pulse on/off time configurations, as well as by dc magnetron sputtering (dcMS), for reference. It is shown that the increase of the pulse off-time from 450 mu s to 3450 mu s, while the pulse on-time is kept constant at 50 mu s, results in an increase of the peak target current (I-Tp) from 3 A to 22 A. The increase of I-Tp is accompanied by an increase of the ion flux towards the growing film. This is particularly pronounced for I-Tp greater than 11 A. The microstructure, the surface topography and the electrical properties of Ag films grown at I-Tp = 11 A, I-Tp = 22 A and by dcMS are investigated, as a function of the film thickness d. It is shown that for d greater than 20 nin the electrical resistivity of films sputtered at I-Tp=22 A is similar to that of films grown by dcMS. Slightly higher values are measured for films grown at I-Tp = 11A. It is found that in this thickness range the film conductivity is strongly affected by the vertical grain size and the scattering of the charged carriers at the film interfaces. For d less than 15 nm the resistivity of films deposited at I-Tp = 22 A is substantially lower as compared to that of films grown by dcMS. Films deposited at I-Tp = 11 A exhibit also in this case a higher conductivity. In this thickness regime the electronic transport and, thus the conductivity are profoundly determined by the surface topography and the film density.
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| 19. |
- Schmidt, Ruediger M., et al.
(författare)
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Increasing the carbon deposition rate using sputter yield amplification upon serial magnetron co-sputtering
- 2014
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 252, s. 74-78
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of carbon based materials by magnetron sputtering suffers frequently from the low deposition rate of carbon due to its low sputtering yield. Here, we describe an approach based on the so-called sputtering yield amplification, which significantly increases the sputtering yield. Carbon has been doped by serial co-sputtering with two different elements, namely tungsten and niobium. Both elements provide a significant rate increase. Addition of 3 at.% of Nb increases the deposition rate of carbon by 130%, whereas the same concentration of W increases it by 280%. TRIDYN simulations have been performed, which reproduce the experimental data. Additionally, our experiments find evidence for very long residence times of the dopant in the target as a result of recoil implantation.
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| 20. |
- Severin, D, et al.
(författare)
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Increase of the Deposition Rate in Reactive Sputtering of Metal Oxides using a Ceramic Nitride Target
- 2009
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 105:9, s. 093302-
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to eliminate hysteresis effects and to increase the deposition rate for the reactive sputtering of metal oxides. This is achieved by using a ceramic nitride target in an argon-oxygen atmosphere. Although the use of a ceramic nitride target leads to pronounced changes of the processing characteristics, incorporation of nitrogen into the growing film is very small. These observations can be theoretically predicted using an extension of Berg's model [S. Berg and T. Nyberg, Thin Solid Films 476, 215 (2005)] to two different reactive gases and a compound target.
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| 21. |
- Severin, Daniel, et al.
(författare)
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Ionenimplantation beim reaktiven Sputtern
- 2005
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Ingår i: Presented at the 69. Annual Meeting of the Deutsche Physikalische Gesellschaft in Berlin, March.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 22. |
- Severin, D., et al.
(författare)
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Tailoring of structure formation and phase composition in reactively sputtered zirconium oxide films using nitrogen as an additional reactive gas
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 103:8, s. 083306-
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Tidskriftsartikel (refereegranskat)abstract
- The structure of ZrO2 films has been controlled during reactive sputtering in an argon/oxygen atmosphere by adding an amount of nitrogen gas to the process. Depending on the deposition conditions, amorphous, cubic, or monoclinic films have been obtained without any additional substrate heating. The resulting film structure is explained in terms of the control of fast negative oxygen ions generated at the target surface and accelerated toward the growing film. Furthermore, the nitrogen addition leads to a pronounced stabilization of the plasma discharge and fewer arcing events, while the incorporation of nitrogen atoms in the growing film is very small.
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| 23. |
- Severin, Daniel, et al.
(författare)
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The Effect of Target Aging on the Structure Formation of Zinc Oxide During Reactive Sputtering
- 2007
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:7-8, s. 3554-3558
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Tidskriftsartikel (refereegranskat)abstract
- A comparative study of reactively sputtered zinc oxide films deposited using (a) a new metallic Zn target and (b) an old one with a pronounced erosion trace is presented. Depending on the shape of the target surface there, are pronounced differences in the film structure. These findings are attributed to a correlation between the target surface profile and ion bombardment of the growing film. Main candidates for the differences in film structure are negatively charged oxygen ions generated at the oxidized target surface.
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| 24. |
- Zalden, Peter, et al.
(författare)
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Femtosecond x-ray diffraction reveals a liquid–liquid phase transition in phase-change materials
- 2019
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Ingår i: Science. - Washington, DC : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6445, s. 1062-1067
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Tidskriftsartikel (refereegranskat)abstract
- In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid–liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics.
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