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D R Mckenzie - One of the best experts on this subject based on the ideXlab platform.
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the structural phases of non crystalline carbon prepared by physical vapour deposition
Carbon, 2009Co-Authors: A Moafi, M B Taylor, J G Partridge, D G Mcculloch, R C Powles, D R MckenzieAbstract:Abstract The structure of non-crystalline carbon films produced using physical vapour deposition is studied as a function of ion impact energy and substrate temperature. The average ion energy was varied from 10 eV to 820 eV using magnetron sputtering and cathodic arc deposition systems while the substrate temperature was varied from room temperature to 640 °C. The Intrinsic Stress, film density and through-film electrical resistance were mapped in the ion energy–temperature plane. These contour plots show the deposition conditions which give rise to Stressed tetrahedral amorphous carbon (ta-C), Stress relieved ta-C and lower density films with a variety of structural forms. Electron microscopy revealed that the microstructure of the low-density forms ranges from highly disordered to various types of oriented graphitic material. The microstructure is determined by the local structural rearrangements that occur due to ion impacts on the picosecond timescale (thermal spikes) and slower relaxation processes which depend on the substrate temperature.
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a comprehensive model of Stress generation and relief processes in thin films deposited with energetic ions
Surface & Coatings Technology, 2006Co-Authors: M M M Bilek, D R MckenzieAbstract:Abstract Levels of Intrinsic Stress in thin films deposited using energetic condensation of ions and/or atoms are known to depend strongly on the energy of the depositing species. At low energies (up to a few eV) thin films are often observed to have a large number of voids and show tensile Stress. As the energy increases, the Stress is observed to rise to a maximum at an intermediate energy—usually at a few tens to a few hundreds of eV. Thereafter as the energy is increased further, the Intrinsic Stress is found to decrease. Variations on this “universal” behaviour occur when species of two quite different energies are deposited whereupon the higher of the two energies seems to determine the level of Intrinsic Stress even when the fraction of ions at that energy is comparatively small. This finding has led to the use of the plasma immersion ion implantation (PIII) method during film deposition to produce coatings with low Stress. Although 98–99% of the ions impacting the substrate have energies in the range which produces very high Intrinsic Stress, the Intrinsic Stress in the film is determined predominantly by the 1–2% of ions with high energy (kV and above). Recent experiments show that Stress relief can be achieved in films deposited with high levels of Stress by post-deposition ion implantation with a non-condensing species, such as argon. We carried out in-situ ellipsometric studies during the implantation and relaxation process, and found that the thickness of the film increased. The increase in thickness in carbon was consistent with a transition of material in the treated volume from sp3 rich to sp2 rich chemical bonding. Atomistic simulations also indicate that the film expands by raising the surface when Stress is relieved by energetic bombardment. Experiments with a variety of materials show that a phase transition or change in preferred orientation occurs during the Stress relief process. This paper will explore the physical processes involved in determining Stress levels in thin films using experimental results together with atomistic simulation. Experimental results of Intrinsic Stress as a function of ion energy when dc bias is applied, so that a high proportion of the depositing species are affected, are compared to results of PIII&D processes where only a small proportion of ions are affected by the applied bias. Mechanisms and simple models of Stress generation and relief are proposed and compared with experiment. The carbon system is examined in detail and the effects of thermal annealing (also found to reduce Stress but with different effects on microstructure) are compared with that of high energy ion bombardment. The differences are explained in terms of the model presented.
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a model for Stress generation and Stress relief mechanisms applied to as deposited filtered cathodic vacuum arc amorphous carbon films
Thin Solid Films, 2005Co-Authors: M M M Bilek, M. Verdon, L Ryves, T W H Oates, D R MckenzieAbstract:Abstract The application of plasma immersion ion implantation (PIII) both during and after the deposition of amorphous carbon by filtered cathodic vacuum arc (FCVA) has been shown to significantly lower the Intrinsic Stress in the coatings. Stress relaxation is found to occur at applied bias as low as 500 V and we observe a trade off between applied bias voltage and pulsing frequency. This paper presents results obtained with pulse bias voltages ranging from 500 V to 20 kV, which show that very thick high strength carbon films suitable for biomedical applications can be grown using this method. In the absence of high voltage pulse biasing during deposition, the Intrinsic Stress in the films is found to depend on the dc bias applied during growth in the way commonly observed in thin film deposition—an initial increase with bias to a maximum followed by a decrease at higher bias. We propose a model to account for the Stress generation energy window commonly observed and to account for the dependence of Stress relief, due to the application of PIII during deposition, on both the applied bias voltage and the pulsing frequency.
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control of Stress and microstructure in cathodic arc deposited films
IEEE Transactions on Plasma Science, 2003Co-Authors: M M M Bilek, D R Mckenzie, R N Tarrant, D G MccullochAbstract:The almost fully ionized cathodic arc plasma is a versatile source for the deposition of thin films. Ion energies impinging on the growth surface can easily be controlled by applying substrate bias. The natural energy of the depositing ions is moderate (tens of electron volts) and generates substantial compressive Stress in most materials. In hard materials (such as tetrahedral-carbon and titanium nitride), the high-yield Stress makes the problem particularly severe. Recent work has shown that Stress relaxation can be achieved by pulses of high ion-energy bombardment (/spl sim/10 keV) applied to the substrate during growth. In this paper, we describe the variation of Intrinsic Stress as a function of applied pulsed bias voltage (V) and pulse frequency (f) for deposition of carbon and titanium nitride films. We found that Stress relaxation depends on the parameter Vf, so it is possible to achieve the same level of Stress relief for a range of voltages by selecting appropriate pulsing frequencies. With the right choice of parameters, it is possible to almost completely eliminate the Intrinsic Stress and deposit very thick coatings. Our experimental results showed correlations between Intrinsic Stress and film microstructures, such as the preferred orientation. This leads to the possibility of controlling microstructure with high energy ion pulsing during growth. Molecular dynamics computer simulations of isolated impacts provide insight into the atomic-scale processes at work. Using the results of such simulations, we describe a model for how Stress relief might take place, based on relaxation in thermal spikes occurring around impact sites of the high-energy ions.
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control of Stress and microstructure in cathodic arc deposited films
International Symposium on Discharges and Electrical Insulation in Vacuum, 2002Co-Authors: M M M Bilek, D R Mckenzie, R N Tarrant, D G MccullochAbstract:The almost fully ionized cathodic arc plasma is a versatile source for the deposition of thin films. The ion energies impinging on the growth surface can easily be controlled by the application of substrate bias. The natural energy of the depositing ions is moderate (/spl sim/10s eV) and generates substantial compressive Stress in most materials. In hard materials such as tetrahedral-carbon and titanium nitride the high yield Stress makes the problem particularly severe. Work has shown that Stress relaxation can be achieved by pulses of high ion energy bombardment (/spl sim/10 kV) applied to the substrate during growth. In this paper we describe the variation of Intrinsic Stress as a function of applied pulsed bias voltage (V) and pulse frequency (f) for the deposition of carbon and titanium nitride films. We show that the Stress relaxation depends on the parameter Vf, so that it is possible achieve the same level of Stress relief for a range of voltages by selecting appropriate pulsing frequencies. With the right choice of parameters it is possible to almost completely eliminate the Intrinsic Stress and deposit very thick coatings. Our experimental results show correlations between Intrinsic Stress and film microstructures, such as the preferred orientation. This leads to the possibility of controlling microstructure with high energy ion pulsing during growth. Molecular dynamics computer simulations of isolated impacts provide insight into the atomic scale processes at work. Using the results of such simulations, we describe a model for how the Stress relief might take place, based on relaxation in thermal spikes occurring around impact sites of the high-energy ions.
J W Chai - One of the best experts on this subject based on the ideXlab platform.
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deposition of iron containing amorphous carbon films by filtered cathodic vacuum arc technique
Diamond and Related Materials, 2001Co-Authors: J S Chen, Gang Chen, Yingtao Li, J W ChaiAbstract:Ž. Iron containing amorphous carbon a-C:Fe films have been deposited with an Fegraphite composite target with different Fe Ž. Ž . content by filtered cathodic vacuum arc FCVA technique. X-Ray induced photoelectron spectroscopy XPS was used to analyze the Fe content in the films. Micro-Raman spectroscopy was employed to characterize the structural changes of a-C:Fe films. The properties of the a-C:Fe films such as the Intrinsic Stress, morphology and roughness investigated by the profiler, atomic force Ž. microscope AFM . The XPS results show that there exists small amount of oxygen in the form of FeO in the films and the Fe fraction in the films is always larger than that in the target. Compared with pure amorphous carbon films the Intrinsic Stress was effectively reduced by incorporating Fe into the films, and decreases with increasing Fe content. As increasing the Fe content, the clusters in the films become finer and the roughness increases The studies of Raman spectra show that the positions of G peak and D peak shift to low and high wavenumbers, respectively, and the ratio of the intensity of D and G peaks increases with an increase in Fe content, that suggests that the sp 2 -bonded carbon and the size of the sp 2 -bonded cluster increases with an increase in the Fe content. 2001 Elsevier Science B.V. All rights reserved.
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deposition of iron containing amorphous carbon films by filtered cathodic vacuum arc technique
Diamond and Related Materials, 2001Co-Authors: J S Chen, Gang Chen, Shu Ping Lau, Zhili Sun, B K Tay, J W ChaiAbstract:Ž. Iron containing amorphous carbon a-C:Fe films have been deposited with an Fegraphite composite target with different Fe Ž. Ž . content by filtered cathodic vacuum arc FCVA technique. X-Ray induced photoelectron spectroscopy XPS was used to analyze the Fe content in the films. Micro-Raman spectroscopy was employed to characterize the structural changes of a-C:Fe films. The properties of the a-C:Fe films such as the Intrinsic Stress, morphology and roughness investigated by the profiler, atomic force Ž. microscope AFM . The XPS results show that there exists small amount of oxygen in the form of FeO in the films and the Fe fraction in the films is always larger than that in the target. Compared with pure amorphous carbon films the Intrinsic Stress was effectively reduced by incorporating Fe into the films, and decreases with increasing Fe content. As increasing the Fe content, the clusters in the films become finer and the roughness increases The studies of Raman spectra show that the positions of G peak and D peak shift to low and high wavenumbers, respectively, and the ratio of the intensity of D and G peaks increases with an increase in Fe content, that suggests that the sp 2 -bonded carbon and the size of the sp 2 -bonded cluster increases with an increase in the Fe content. 2001 Elsevier Science B.V. All rights reserved.
Christoph Hollenstein - One of the best experts on this subject based on the ideXlab platform.
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dependence of Intrinsic Stress in hydrogenated amorphous silicon on excitation frequency in a plasma enhanced chemical vapor deposition process
Journal of Applied Physics, 1992Co-Authors: Joydeep Dutta, U Kroll, Patrick Chabloz, A A Howling, J L Dorier, Arvind Shah, Christoph HollensteinAbstract:Dependence of Intrinsic Stress in hydrogenated amorphous silicon on excitation frequency in a plasma-enhanced chemical vapor deposition process
C Polop - One of the best experts on this subject based on the ideXlab platform.
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disclosing the origin of the postcoalescence compressive Stress in polycrystalline films by nanoscale Stress mapping
Physical Review B, 2018Co-Authors: E Vasco, E G Michel, C PolopAbstract:A method based on atomic force microscopy, which allows mapping the residual Stress at nanoscale on the surface of crystalline solids [Polop et al., Nanoscale 9, 13938 (2017)], sheds light on the controversial origin of the Intrinsic compression that arises in continuous polycrystalline films under high atomic mobility conditions. The maps of residual Stress reveal that the compression is concentrated in narrow strips adjacent and parallel to the grain-boundary triple junctions, but not inside the grain boundary as usually assumed. We explain these findings in the light of Mullins's theory for surface diffusion of adatoms towards grain boundaries. As the surface slope at the grain-boundary triple junctions is constrained by the balance between interfacial tensions, the kinetic surface profile is different from the mechanical equilibrium profile predicted by the Laplace-Young equation. Where the curvatures of both profiles differ, an Intrinsic Stress is generated in the form of Laplace pressure. The average value of the Stress profile is compressive. In turn, the resulting Stress induces a Srolovitz-type surface diffusion, which counters the Mullins-type diffusion. The competition between both diffusion mechanisms addresses the main fingerprints of the Intrinsic Stress behavior in polycrystalline films, namely, the stabilization of the Stress profile during growth, its reversibility with the flux, and the kinetics of the Stress relaxation and recovery.
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Intrinsic compressive Stress in polycrystalline films is localized at edges of the grain boundaries
Physical Review Letters, 2017Co-Authors: E Vasco, C PolopAbstract:The Intrinsic compression that arises in polycrystalline thin films under high atomic mobility conditions has been attributed to the insertion or trapping of adatoms inside grain boundaries. This compression is a consequence of the Stress field resulting from imperfections in the solid and causes the thermomechanical fatigue that is estimated to be responsible for 90% of mechanical failures in current devices. We directly measure the local distribution of residual Intrinsic Stress in polycrystalline thin films on nanometer scales, using a pioneering method based on atomic force microscopy. Our results demonstrate that, at odds with expectations, compression is not generated inside grain boundaries but at the edges of gaps where the boundaries intercept the surface. We describe a model wherein this compressive Stress is caused by Mullins-type surface diffusion towards the boundaries, generating a kinetic surface profile different from the mechanical equilibrium profile by the Laplace-Young equation. Where the curvatures of both profiles differ, an Intrinsic Stress is generated in the form of Laplace pressure. The Srolovitz-type surface diffusion that results from the Stress counters the Mullins-type diffusion and stabilizes the kinetic surface profile, giving rise to a steady compression regime. The proposed mechanism of competition between surface diffusions would explain the flux and time dependency of compressive Stress in polycrystalline thin films.
M M M Bilek - One of the best experts on this subject based on the ideXlab platform.
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a comprehensive model of Stress generation and relief processes in thin films deposited with energetic ions
Surface & Coatings Technology, 2006Co-Authors: M M M Bilek, D R MckenzieAbstract:Abstract Levels of Intrinsic Stress in thin films deposited using energetic condensation of ions and/or atoms are known to depend strongly on the energy of the depositing species. At low energies (up to a few eV) thin films are often observed to have a large number of voids and show tensile Stress. As the energy increases, the Stress is observed to rise to a maximum at an intermediate energy—usually at a few tens to a few hundreds of eV. Thereafter as the energy is increased further, the Intrinsic Stress is found to decrease. Variations on this “universal” behaviour occur when species of two quite different energies are deposited whereupon the higher of the two energies seems to determine the level of Intrinsic Stress even when the fraction of ions at that energy is comparatively small. This finding has led to the use of the plasma immersion ion implantation (PIII) method during film deposition to produce coatings with low Stress. Although 98–99% of the ions impacting the substrate have energies in the range which produces very high Intrinsic Stress, the Intrinsic Stress in the film is determined predominantly by the 1–2% of ions with high energy (kV and above). Recent experiments show that Stress relief can be achieved in films deposited with high levels of Stress by post-deposition ion implantation with a non-condensing species, such as argon. We carried out in-situ ellipsometric studies during the implantation and relaxation process, and found that the thickness of the film increased. The increase in thickness in carbon was consistent with a transition of material in the treated volume from sp3 rich to sp2 rich chemical bonding. Atomistic simulations also indicate that the film expands by raising the surface when Stress is relieved by energetic bombardment. Experiments with a variety of materials show that a phase transition or change in preferred orientation occurs during the Stress relief process. This paper will explore the physical processes involved in determining Stress levels in thin films using experimental results together with atomistic simulation. Experimental results of Intrinsic Stress as a function of ion energy when dc bias is applied, so that a high proportion of the depositing species are affected, are compared to results of PIII&D processes where only a small proportion of ions are affected by the applied bias. Mechanisms and simple models of Stress generation and relief are proposed and compared with experiment. The carbon system is examined in detail and the effects of thermal annealing (also found to reduce Stress but with different effects on microstructure) are compared with that of high energy ion bombardment. The differences are explained in terms of the model presented.
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a model for Stress generation and Stress relief mechanisms applied to as deposited filtered cathodic vacuum arc amorphous carbon films
Thin Solid Films, 2005Co-Authors: M M M Bilek, M. Verdon, L Ryves, T W H Oates, D R MckenzieAbstract:Abstract The application of plasma immersion ion implantation (PIII) both during and after the deposition of amorphous carbon by filtered cathodic vacuum arc (FCVA) has been shown to significantly lower the Intrinsic Stress in the coatings. Stress relaxation is found to occur at applied bias as low as 500 V and we observe a trade off between applied bias voltage and pulsing frequency. This paper presents results obtained with pulse bias voltages ranging from 500 V to 20 kV, which show that very thick high strength carbon films suitable for biomedical applications can be grown using this method. In the absence of high voltage pulse biasing during deposition, the Intrinsic Stress in the films is found to depend on the dc bias applied during growth in the way commonly observed in thin film deposition—an initial increase with bias to a maximum followed by a decrease at higher bias. We propose a model to account for the Stress generation energy window commonly observed and to account for the dependence of Stress relief, due to the application of PIII during deposition, on both the applied bias voltage and the pulsing frequency.
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control of Stress and microstructure in cathodic arc deposited films
IEEE Transactions on Plasma Science, 2003Co-Authors: M M M Bilek, D R Mckenzie, R N Tarrant, D G MccullochAbstract:The almost fully ionized cathodic arc plasma is a versatile source for the deposition of thin films. Ion energies impinging on the growth surface can easily be controlled by applying substrate bias. The natural energy of the depositing ions is moderate (tens of electron volts) and generates substantial compressive Stress in most materials. In hard materials (such as tetrahedral-carbon and titanium nitride), the high-yield Stress makes the problem particularly severe. Recent work has shown that Stress relaxation can be achieved by pulses of high ion-energy bombardment (/spl sim/10 keV) applied to the substrate during growth. In this paper, we describe the variation of Intrinsic Stress as a function of applied pulsed bias voltage (V) and pulse frequency (f) for deposition of carbon and titanium nitride films. We found that Stress relaxation depends on the parameter Vf, so it is possible to achieve the same level of Stress relief for a range of voltages by selecting appropriate pulsing frequencies. With the right choice of parameters, it is possible to almost completely eliminate the Intrinsic Stress and deposit very thick coatings. Our experimental results showed correlations between Intrinsic Stress and film microstructures, such as the preferred orientation. This leads to the possibility of controlling microstructure with high energy ion pulsing during growth. Molecular dynamics computer simulations of isolated impacts provide insight into the atomic-scale processes at work. Using the results of such simulations, we describe a model for how Stress relief might take place, based on relaxation in thermal spikes occurring around impact sites of the high-energy ions.
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control of Stress and microstructure in cathodic arc deposited films
International Symposium on Discharges and Electrical Insulation in Vacuum, 2002Co-Authors: M M M Bilek, D R Mckenzie, R N Tarrant, D G MccullochAbstract:The almost fully ionized cathodic arc plasma is a versatile source for the deposition of thin films. The ion energies impinging on the growth surface can easily be controlled by the application of substrate bias. The natural energy of the depositing ions is moderate (/spl sim/10s eV) and generates substantial compressive Stress in most materials. In hard materials such as tetrahedral-carbon and titanium nitride the high yield Stress makes the problem particularly severe. Work has shown that Stress relaxation can be achieved by pulses of high ion energy bombardment (/spl sim/10 kV) applied to the substrate during growth. In this paper we describe the variation of Intrinsic Stress as a function of applied pulsed bias voltage (V) and pulse frequency (f) for the deposition of carbon and titanium nitride films. We show that the Stress relaxation depends on the parameter Vf, so that it is possible achieve the same level of Stress relief for a range of voltages by selecting appropriate pulsing frequencies. With the right choice of parameters it is possible to almost completely eliminate the Intrinsic Stress and deposit very thick coatings. Our experimental results show correlations between Intrinsic Stress and film microstructures, such as the preferred orientation. This leads to the possibility of controlling microstructure with high energy ion pulsing during growth. Molecular dynamics computer simulations of isolated impacts provide insight into the atomic scale processes at work. Using the results of such simulations, we describe a model for how the Stress relief might take place, based on relaxation in thermal spikes occurring around impact sites of the high-energy ions.
