| 1. |
- Broitman, Esteban, et al.
(författare)
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Structural and Mechanical Properties of CNx and CPx Thin Solid Films
- 2012
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Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 488-489, s. 581-584
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Tidskriftsartikel (refereegranskat)abstract
- The inherent resiliency, hardness and relatively low friction coefficient of the fullerene-like (FL) allotrope of carbon nitride (CNx) thin solid films give them potential in numerous tribological applications. In this work, we study the substitution of N with P to grow FL-CPx to achieve better cross- and inter-linking of the graphene planes, improving thus the materials mechanical and tribological properties. The CNx and CPx films have been synthesized by DC magnetron sputtering. HRTEM have shown the CPx films exhibit a short range ordered structure with FL characteristics for substrate temperature of 300 degrees C and for a phosphorus content of 10-15 at.%. These films show better mechanical properties in terms of hardness and resiliency compared to those of the FL-CNx films. The low water adsorption of the films is correlated to the theoretical prediction for low density of dangling bonds in both, CNx and CPx. First-principles calculations based on Density Functional Theory (DFT) were performed to provide additional insight on the structure and bonding in CNx, CPx and a-C compounds.
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| 2. |
- Chubarov, Mikhail, et al.
(författare)
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Nucleation and initial growth of sp2-BNon α-Al2O3 and SiC by chemical vapour deposition
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Knowledge on thin films evolution from the early stages of growth is important for the control of quality and properties of the film. Here we present study of the early growth stages and evolution of the crystalline structure of sp2 hybridised Boron Nitride (BN) thin films deposited by chemical vapour deposition from triethyl boron and ammonia. Nucleation of hexagonal BN (h-BN) is observed already at 1200 °C on α-Al2O3 substrate with an AlN buffer layer (AlN/α-Al2O3) while no formation of h-BN is detected when the growth is done on 6H-SiC in a growth temperature range between 1200 °C and 1700 °C. We demonstrate that h-BN grows on AlN/α-Al2O3 exhibiting a layer-by-layer growth mode up to ca. 4 nm followed by a transition to r-BN growth when grown at 1500 °C. The following r-BN growth is suggested to proceed with mixed layer-by-layer and island growth mode; after a thin continuous layer of r-BN, islands formation is favoured leading to a twinned r-BN structure of the film. We find that h-BN does not grow on 6H-SiC substrates instead r-BN nucleates and grows directly as a twinned crystal. The twinning is found to be suppressed by a surface preparation of the SiC substrate with SiH4 prior to BN growth. These results open up for a more controlled epitaxial growth of sp2-BN for future electronic applications.
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| 3. |
- Czigany, Zsolt, et al.
(författare)
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Interpretation of electron diffraction patterns from amorphous and fullerene-like carbon allotropes
- 2010
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Ingår i: Ultramicroscopy. - : Elsevier Science B.V., Amsterdam.. - 0304-3991 .- 1879-2723. ; 110:7, s. 815-819
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Tidskriftsartikel (refereegranskat)abstract
- The short range order in amorphous and fullerene-like carbon compounds has been characterized by selected area electron diffraction (SAED) patterns and compared with simulations of model nanoclusters. Broad rings in SAED pattern from fullerene-like CNx at similar to 1.2, similar to 2, and similar to 3.5 angstrom indicate short-range order similar to that in graphite, but peak shifts indicate sheet curvature in agreement with high-resolution transmission electron microscopy images. Fullerene-like CPx exhibits rings at similar to 1.6 and 2.6 angstrom, which can be explained if it consists of fragments with short-range order and high curvature similar to that of C-20.
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| 4. |
- Furlan, Andrej, 1974-, et al.
(författare)
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Structure and properties of phosphorus-carbide thin solid films
- 2013
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 548:2, s. 247-254
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorus-carbide (CPx) thin films have been deposited by unbalanced reactive magnetron sputtering and investigated by TEM, XPS, SEM, ERDA, Raman scattering spectroscopy, nanoindentation testing, and four-point electrical probe techniques. As-deposited films with x=0.1 are electron amorphous with elements of FL structure and high mechanical resiliency with hardness of 34.4 GPa and elastic recovery of 72%. The electrical resistivity of the films are in the range 0.4-1.7 Ωcm for CP0.027, 1.4-22.9 Ωcm for CP0.1, and lower than the minimal value the four-point probe is able to detect for CPx with x≥0.2.
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| 5. |
- Höglund, Carina, et al.
(författare)
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Effects of volume mismatch and electronic structure on the decomposition of ScAlN and TiAlN solid solutions
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:22, s. 224101-
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Tidskriftsartikel (refereegranskat)abstract
- Thin solid films of metastable rocksalt structure (c-) Sc1-xAlxN and Ti1-xAlxN were employed as model systems to investigate the relative influence of volume mismatch and electronic structure driving forces for phase separation. Reactive dual magnetron sputtering was used to deposit stoichiometric Sc0.57Al0.43N(111) and Ti0.51Al0.49N(111) thin films, at 675 °C and 600 °C, respectively, followed by stepwise annealing to a maximum temperature of 1100 °C. Phase transformations during growth and annealing were followed in situ using X-ray scattering. The results show that the as-deposited Sc0.57Al0.43N films phase separate at 1000 °C – 1100 °C into non-isostructural c-ScN and wurtzite-structure (w-) AlN, via nucleation and growth at domain boundaries. Ti0.51Al0.49N, however, exhibits spinodal decomposition into isostructural coherent c-TiN and c-AlN, in the temperature interval of 800 °C – 1000 °C. X-ray pole figures show the coherency between c-ScN and w-AlN, with AlN(0001) || ScN(001) and AlN<01ɸ10> || ScN<1ɸ10>. First principles calculations of mixing energy-lattice spacing curves explain the results on a fundamental physics level and open a route for design of novel metastable pseudobinary phases for hard coatings and electronic materials.
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| 6. |
- Höglund, Carina, et al.
(författare)
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Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy : structural characterization and first-principles calculations
- 2010
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 107:12, s. 123515-
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Tidskriftsartikel (refereegranskat)abstract
- AlN(0001) was alloyed with ScN with molar fractions up to ~22%, while retaining a singlecrystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al2O3(0001) and MgO(111) substrates. Films with ScN contents between 23% and ~50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt-structure Sc1-xAlxN(111) films. The experimental results are analyzed with ion beam analysis, X-ray diffraction, and transmission electron microscopy, together with ab-initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.
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| 7. |
- Schmidt, Susann, et al.
(författare)
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Influence of inert gases on the reactive high power pulsed magnetron sputtering process of carbon-nitride thin films
- 2013
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 31:1, s. 011503-
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Tidskriftsartikel (refereegranskat)abstract
- The influence of inert gases (Ne, Ar, Kr) on the sputter process of carbon and carbon-nitride (CNx) thin films was studied using reactive high power pulsed magnetron sputtering (HiPIMS). Thin solid films were synthesized in an industrial deposition chamber from a graphite target. The peak target current during HiPIMS processing was found to decrease with increasing inert gas mass. Time averaged and time resolved ion mass spectroscopy showed that the addition of nitrogen, as reactive gas, resulted in less energetic ion species for processes employing Ne, whereas the opposite was noticed when Ar or Kr were employed as inert gas. Processes in nonreactive ambient showed generally lower total ion fluxes for the three different inert gases. As soon as N-2 was introduced into the process, the deposition rates for Ne and Ar-containing processes increased significantly. The reactive Kr-process, in contrast, showed slightly lower deposition rates than the nonreactive. The resulting thin films were characterized regarding their bonding and microstructure by x-ray photoelectron spectroscopy and transmission electron microscopy. Reactively deposited CNx thin films in Ar and Kr ambient exhibited an ordering toward a fullerene-like structure, whereas carbon and CNx films deposited in Ne atmosphere were found to be amorphous. This is attributed to an elevated amount of highly energetic particles observed during ion mass spectrometry and indicated by high peak target currents in Ne-containing processes. These results are discussed with respect to the current understanding of the structural evolution of a-C and CNx thin films.
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| 8. |
- Tucker, Mark, et al.
(författare)
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Filtered pulsed cathodic arc deposition of fullerene-like carbon and carbon nitride films
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:14, s. 144312-
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Tidskriftsartikel (refereegranskat)abstract
- Carbon and carbon nitride films (CNx , 0 ≤ x ≤ 0.26) were deposited by filtered pulsed cathodic arc and were investigated using transmission electron microscopy and X-ray photoelectron spectroscopy. A “fullerene-like” (FL) structure of ordered graphitic planes, similar to that of magnetron sputtered FL-CNx films, was observed in films deposited at 175 °C and above, with N2 pressures of 0 and 0.5 mTorr. Higher substrate temperatures and significant nitrogen incorporation are required to produce similar FL structure by sputtering, which may, at least in part, be explained by the high ion charge states and ion energies characteristic of arc deposition. A gradual transition from majority sp3-hybridized films to sp2 films was observed with increasing substrate temperature. High elastic recovery, an attractive characteristic mechanical property of FL-CNx films, is evident in arc-deposited films both with and without nitrogen content, and both with and without FL structure.
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