| 1. |
- Eklund, Per, et al.
(författare)
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Microstructure and electrical properties of Ti-Si-C-Ag nanocomposite thin films
- 2007
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 201:14, s. 6465-6469
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Tidskriftsartikel (refereegranskat)abstract
- Ti-Si-C-Ag nanocomposite coatings consisting of nanocrystalline TiC in an amorphous Si matrix with segregated Ag were deposited by dual magnetron sputtering from Ti3SiC2 and Ag targets. As evidenced by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, for Ag contents below 10 at.%, the Ag forms similar to 10 nm large crystallites that are homogeneously distributed in the films. For higher Ag contents, coalescence during growth results in the formation of > similar to 100 nm Ag islands on the film surface. The electrical resistivity of the coatings was measured in a four-point-probe setup, and ranged from 340 mu Omega cm (for Ti-Si-C coatings without Ag) to 40 mu Omega cm (for high Ag content).
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| 2. |
- Andersson, Jon M., et al.
(författare)
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Microstructure of α-alumina thin films deposited at low temperatures on chromia template layers
- 2004
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 22:1, s. 117-121
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Tidskriftsartikel (refereegranskat)abstract
- Radio frequency sputtering has been used to deposit -alumina (-Al2O3) thin films at substrate temperatures of 280–560 °C. The films are shown to be single phased and hard. Nanoindentation gives values of 306±31 and 27±3 GPa for elastic modulus and hardness, respectively, for a substrate temperature of 280 °C. Growth of the phase was achieved by in situ predeposition of a chromia template layer. Chromia crystallizes in the same hexagonal structure as -alumina, with a lattice mismatch of 4.1% in the a- and 4.6% in the c-parameter, and is shown to nucleate readily on the amorphous substrates (silicon with a natural oxide layer). This results in local epitaxy of -alumina on the chromia layer, as is shown by transmission electron microscopy. The alumina grains are columnar with grain widths increasing from 22±7 to 41±9 nm, as the temperature increases from 280 to 560 °C. This is consistent with a surface diffusion dominated growth mode and suggests that -alumina deposition at low temperatures is possible once initial grain nucleation has occurred. Results are also presented demonstrating chromia/-alumina growth on a technological substrate (Haynes230 Ni-based super alloy, Haynes International, Inc.).
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| 3. |
- Berlind, Torun, 1965-, et al.
(författare)
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Spectroscopic ellipsometry characterization of amorphous carbon and amorphous,graphitic and fullerene-like carbon nitride thin films
- 2009
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 517:24, s. 6652-6658
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nitride (CNx) and amorphous carbon (a-C) thin films are deposited by reactive magnetron sputtering onto silicon (001) wafers under controlled conditions to achieve amorphous, graphitic and fullerene-like microstructures. As-deposited films are analyzed by Spectroscopic Ellipsometry in the UV–VIS–NIR and IR spectral ranges in order to get further insight into the bonding structure of the material. Additional characterization is performed by High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Between eight and eleven resonances are observed and modeled in the ellipsometrically determined optical spectra of the films. The largest or the second largest resonance for all films is a feature associated with C–N or C–C modes. This feature is generally associated with sp3 C–N or sp3 C–C bonds, which for the nitrogen-containing films instead should be identified as a three-fold or two-fold sp2 hybridization of N, either substituted in a graphite site or in a pyridine-like configuration, respectively. The π→πlow asterisk electronic transition associated with sp2 C bonds in carbon films and with sp2 N bonds (as N bonded in pyridine-like manner) in CNx films is also present, but not as strong. Another feature present in all CNx films is a resonance associated with nitrile often observed in carbon nitrides. Additional resonances are identified and discussed and moreover, several new, unidentified resonances are observed in the ellipsometric spectra.
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| 4. |
- Broitman, Esteban, et al.
(författare)
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Industrial-scale deposition of highly adherent CNx films on steel substrates
- 2010
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Ingår i: Surface & Coatings Technology. - : Elsevier Science B.V., Amsterdam.. - 0257-8972 .- 1879-3347. ; 204:21-22, s. 3349-3357
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Tidskriftsartikel (refereegranskat)abstract
- Highly adherent carbon nitride (CNx) films were deposited using a novel pretreatment with two high power impulse magnetron sputtering (HIPIMS) power supplies in a master-slave configuration: one to establish the discharge and one to produce a pulsed substrate bias. During the pretreatment, SKF3 (AISI 52100) steel substrates were pulse-biased in the environment of a HIPIMS Cr plasma in order to sputter clean the surface and to implant Cr metal ions. Subsequently. CNx films were prepared at room temperature by DC unbalanced magnetron sputtering from a high purity graphite target in a N-2/Ar discharge at 3 mTorr. All processing was done in an industrial CemeCon CC800 system. A series of depositions were obtained with samples at different bias voltages (DC and pulsed) in the range of 0-800 V. Scanning transmission microscopy (STEM) and high resolution transmission electron microscopy (HRTEM) show the formation of an interface comprising a polycrystalline Cr layer of 100 nm and an amorphous transition layer of 5 nm. The adhesion of CNx films evaluated by the Daimler-Benz Rockwell-C reach strength quality HF1, and the scratch tests gives critical loads of 84 N. Adhesion results are correlated to the formation of an optimal interfacial mixing layer of Cr and steel.
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| 5. |
- Broitman, E., et al.
(författare)
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Structural and mechanical properties of diamond-like carbon films deposited by direct current magnetron sputtering
- 2003
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 21:4, s. 851-859
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Tidskriftsartikel (refereegranskat)abstract
- A systematic study of physical properties of sputter-deposited DLC films was performed as a function of flux ratio and ion energy. The energy and flux ions and neutral atoms impinging on the surface of the growing films were deduced from Langmuir probe measurements and theoretical calculations. The bombardment of growing films by the energetic particles led to changes in microstructure and mechanical properties. Results suggest that the presence of defective graphite formed by subplanted C and Ar atoms is the dominant influence on the mechanical properties of the DLC films.
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| 6. |
- Broitman, E., et al.
(författare)
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Water adsorption on phosphorous-carbide thin films
- 2009
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 204:6-7, s. 1035-1039
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous phosphorous-carbide films have been considered as a new tribological coating material with unique electrical properties. However, such CPx films have not found practical use until now because they tend to oxidize/hydrolyze rapidly when in contact with air. Recently, we demonstrated that CPx thin films with a fullerene-like structure can be deposited by magnetron sputtering, whereby the structural incorporation of P atoms induces the formation of strongly bent and inter-linked graphene planes. Here, we compare the uptake of water in fullerene-like phosphorous-carbide (FL-CPx) thin films with that in amorphous phosphorous-carbide (a-CPx), and amorphous carbon (a-C) thin films. Films of each material were deposited on quartz crystal substrates by reactive DC magnetron sputtering to a thickness in the range 100-300 nm. The film microstructure was characterized by X-ray photoelectron spectroscopy, and high resolution transmission electron microscopy. A quartz crystal microbalance placed in a vacuum chamber was used to measure their water adsorption. Measurements indicate that FL-CPx films adsorbed less water than the a-CPx and a-C ones. To provide additional insight into the atomic structure of defects in the FL-CPx and a-CPx compounds, we performed first-principles calculations within the framework of density functional theory. Cohesive energy comparison reveals that the energy cost formation for dangling bonds in different configurations is considerably higher in FL-CPx than for the amorphous films. Thus, the modeling confirms the experimental results that dangling bonds are less likely in FL-CPx than in a-CPx and a-C films.
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| 7. |
- Chubarov, M., et al.
(författare)
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Chemical vapour deposition of epitaxial rhombohedral BN thin films on SiC substrates
- 2014
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Ingår i: CrystEngComm. - : Royal Society of Chemistry. - 1466-8033. ; 16:24, s. 5430-5436
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial growth of rhombohedral boron nitride (r-BN) on different polytypes of silicon carbide (SiC) is demonstrated using thermally activated hot-wall chemical vapour deposition and triethyl boron and ammonia as precursors. With respect to the crystalline quality of the r-BN films, we investigate the influence of the deposition temperature, the precursor ratio (N/B) and the addition of a minute amount of silicon to the gas mixture. From X-ray diffraction and transmission electron microscopy, we find that the optimal growth temperature for epitaxial r-BN on the Si-face of the SiC substrates is 1500 degrees C at a N/B ratio of 642 and silicon needs to be present not only in the gas mixture during deposition but also on the substrate surface. Such conditions result in the growth of films with a c-axis identical to that of the bulk material and a thickness of 200 nm, which is promising for the development of BN films for electronic applications.
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| 8. |
- Czigany, Zs., et al.
(författare)
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Growth of fullerene-like carbon nitride thin solid films consisting of cross-linked nano-onions
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 79:16, s. 2639-2641
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Tidskriftsartikel (refereegranskat)abstract
- Fullerene-like CNx (x˜0.12) thin solid films were deposited by reactive magnetron sputtering of graphite in a nitrogen and argon discharge on cleaved NaCl and Si(001) substrates at 450°C. As-deposited films consist of 5 nm diam CNx nano-onions with shell sizes corresponding to Goldberg polyhedra determined by high-resolution transmission electron microscopy. Electron energy loss spectroscopy revealed that N incorporation is higher in the core of the onions than at the perimeter. N incorporation promotes pentagon formation and provides reactive sites for interlinks between shells of the onions. A model is proposed for the formation of CNx nano-onions by continuous surface nucleation and growth of hemispherical shells. © 2001 American Institute of Physics.
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| 9. |
- Czigany, Zs., et al.
(författare)
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Imaging of fullerene-like structures in CNx thin films by electron microscopy, Sample preparation artefacts due to ion-beam milling
- 2003
-
Ingår i: Ultramicroscopy. - 0304-3991 .- 1879-2723. ; 94:3-4, s. 163-173
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure of CNx thin films, deposited by reactive magnetron sputtering, was investigated by transmission electron microscopy (TEM) at 200kV in plan-view and cross-sectional samples. Imaging artefacts arise in high-resolution TEM due to overlap of nm-sized fullerene-like features for specimen thickness above 5nm. The thinnest and apparently artefact-free areas were obtained at the fracture edges of plan-view specimens floated-off from NaCl substrates. Cross-sectional samples were prepared by ion-beam milling at low energy to minimize sample preparation artefacts. The depth of the ion-bombardment-induced surface amorphization was determined by TEM cross sections of ion-milled fullerene-like CNx surfaces. The thickness of the damaged surface layer at 5° grazing incidence was 13 and 10nm at 3 and 0.8keV, respectively, which is approximately three times larger than that observed on Si prepared under the same conditions. The shallowest damage depth, observed for 0.25keV, was less than 1nm. Chemical changes due to N loss and graphitization were also observed by X-ray photoelectron spectroscopy. As a consequence of chemical effects, sputtering rates of CNx films were similar to that of Si, which enables relatively fast ion-milling procedure compared to carbon compounds. No electron beam damage of fullerene-like CNx was observed at 200kV. © 2002 Elsevier Science B.V. All rights reserved.
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| 10. |
- Kostov Gueorguiev, Gueorgui, et al.
(författare)
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Intercalation of P atoms in Fullerene-like CPx
- 2011
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Ingår i: CHEMICAL PHYSICS LETTERS. - : Elsevier Science B.V., Amsterdam.. - 0009-2614 .- 1873-4448. ; 501:4-6, s. 400-403
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Tidskriftsartikel (refereegranskat)abstract
- The energy cost for P atom intercalation and corresponding structural implications during formation of Fullerene-like Phosphorus carbide (FL-CPx) were evaluated within the framework of Density Functional Theory. Single P atom interstitial defects in FL-CPx are energetically feasible and exhibit energy cost of 0.93-1.21 eV, which is comparable to the energy cost for experimentally confirmed tetragon defects and dangling bonds in CPx. A single P atom intercalation event in FL-CPx can increase the inter-sheet distance from 3.39-3.62 angstrom to 5.81-7.04 angstrom. These theoretical results are corroborated by Selected Area Electron Diffraction characterization of FL-CPx samples.
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