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Kleinsorge, Britta Yvonne. "Doping of amorphous carbon." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621744.
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Ferrari, Andrea Carlo. "Nanoscale properties of amorphous carbon." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621037.
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Satyanarayana, Bukinakere Subbakrishniah. "Field emission from tetrahedral amorphous carbon." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621638.
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Jones, Todd J. Tombrello Thomas A. "Radiation-induced conductivity in amorphous carbon /." Diss., Pasadena, Calif. : California Institute of Technology, 1989. http://resolver.caltech.edu/CaltechETD:etd-02022007-131335.
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Walters, Jennifer. "The structure of amorphous hydrogenated carbon." Thesis, University of Kent, 1995. https://kar.kent.ac.uk/38837/.
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The structure of several amorphous hydrogenated carbon (a-C:H) samples has been studied in detail using time-of-flight neutron diffraction, inelastic neutron scattering, infrared spectroscopy and reverse Monte Carlo (RMC) computer modelling. Supplementary work has also included combustion analysis. The results are presented as evidence for a new structural model for a-C:H. The high-resolution real-space neutron diffraction data allows direct determination of the single:double bond ratio, and also shows the presence of sp1 hybridised carbon bonding environments in some samples. There is limited evidence for the presence of molecular hydrogen "trapped" within the amorphous network. The spectroscopic data is then used to provide information on the C-H bonding environments, so that using a combination of experimental techniques a detailed picture of the atomic scale structure has been produced. For the hand carbon samples, prepared using acetylene and propane, the carbon-atom sites are found to be predominantly sp2 bonded, with a single:double bond ratio for carbon-carbon bonds of about 2.5:1. The effect of beam energy on the structure of the material is also investigated, and comparison made between samples prepared using a fats-atom (neutral particle)source and those prepared by plasma enhanced chemical vapour deposition, from acetylene. The results show that in both deposition methods, increasing the beam energy produces a lower total sp2 hybridised carbon content in the material with evidence for a shift from pure olefinic to some aromatic/graphitic bonding in one sample. This trend to a more aromatic bonding environment is also observed in samples prepared from a cyclohexane precursor. The spectroscopy results show that for all samples the hydrogen bonding environments are similar, although there is some evidence for changes in the distribution of hydrogen within the network with deposition energy. The spectra for all the samples show similarities to those for the polymeric materials, polyethylene and rubber. In addition, the results of a study of the structure of a-C:H up to a maximum of 1000c are presented. The data show clearly the effect on atomic correlations of elevated temperatures, with the initial room-temperature amorphous network (a mixture of single bonds and olefinic double bonds) becoming progressively aromatic, the graphite as hydrogen is evolved. Infrared spectroscopy results would seem to indicate that sp3 CH is the primary source of hydrogen for effusion, such that, on annealing, molecular hydrogen is formed wherever there are two neighboring hydrogen atoms. Structural transformations are seen to occur throughout the heating process. Finally, the RMC method has been used to produce a model for the structure of a-C:H, by fitting to experimental data from neutron and X-ray diffraction experiments. The RMC method was implemented with the introduction of additional constraints on the minimum number of atoms in a ring, and on the maximum coordination number. Once the data has been fitted, it is possible to generate model partial pair distribution functions, bond angle distributions, coordination number distributions, etc. By fitting all the experimental data sets simultaneously, there is sufficient information to generate a viable "physical" model for the structure of these materials. The effects of increasing number density within the model have also been investigated, and this confirmed that the density is a crucial parameter in the modelling process.
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Honeybone, P. J. R. "Neutron scattering studies of amorphous hydrogenated carbon and silcon carbon." Thesis, University of Kent, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317306.
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TASAYCO, CARLOS MANUEL SANCHEZ. "NITROGEN INCORPORATION INTO AMORPHOUS FLUORINATED CARBON FILMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3698@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOAs propriedades tribológicas de revestimentos de carbono usados em discos rígidos magnéticos foram de enorme importância para o contínuo aumento da densidade de informação armazenada nos mesmos. As características mecânicas e estruturais de filmes de carbono amorfo também foram indispensáveis para o desenvolvimento de revestimentos que atendessem às especificações do desenvolvimento destes dispositivos: alta dureza e densidade, além de baixo coeficiente de atrito e alta resistência ao desgaste. Neste trabalho são apresentados os efeitos da incorporação de nitrogênio em filmes de carbono fluorado (a-C:H:F) depositados pela técnica de deposição por vapor químico assistido por plasma. As propriedades mecânicas e estruturais foram investigadas com o uso das técnicas nucleares (retroespalhamento Rutherford, detecção de recuo elástico, reação nuclear), espectroscopia de fotoelétrons induzidos por raios-X, medidas de tensão interna (por perfilometria), espectroscopia de absorção no infravermelho, espectroscopia Raman, microscopia de força atômica e medidas de ângulo de contato. Foi depositada uma série de filmes onde foi variada a pressão de N2 em uma atmosfera precursora de CH4-CF4 (1:2) (PN2 = 0% até 60%). A tensão de autopolarização foi fixada em - 350V. Os resultados obtidos mostram que as propriedades dos filmes são controladas pela incorporação de nitrogênio que chega a 20 at.%. Identificou-se um decaimento na taxa de deposição com o incremento da pressão parcial de N2, e um sensível decaimento na concentração de flúor. O filme fica menos tensionado, o que pode resultar em uma melhoria na adesão. Entretanto, o ângulo de contato diminui, resultando em um aumento no coeficiente de atrito. Novos estudos procurando aumentar simultaneamente as concentrações de F e N são sugeridos.
The tribological properties of carbon coatings of hard magnetic disks played an important role for the continuous increase of their storage capacity. The mechanical and structural properties were also important: high density, hardness and wear resistance, and low friction coefficient. In this work, we study the effects of the nitrogen incorporation into fluorinated carbon films (a-C:H:F) deposited by plasma enhanced chemical vapor deposition. The film properties were investigated by using a multitechnique approach: nuclear techniques (Rutherford backscattering, elastic recoil and nuclear reaction analyses), x-ray photoelectron spectroscopy, internal stress measurements by perfilometry, Raman and Infrared spectroscopies, atomic force microscopy and contact angle measurements. Films were deposited changing the N2 partial pressure in a precursor atmosphere also composed by a fixed CH4-CF4 mixture (1:2) (PN2: 0 - 60%), with the self-bias voltage of -350V. The results show that the film properties are controlled by the nitrogen incorporation, with an important fluorine content reduction. The internal stress reduction may result in an increase of the film adhesion. However, the contact angle decreases upon nitrogen incorporation, resulting in an increase of the friction coefficient. New studies with the goal of obtain a simultaneous increase of both fluorine and nitrogen content are suggested.
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Miriyala, Nikhila. "Porous carbon carriers for amorphous drug delivery." Thesis, Aston University, 2018. http://publications.aston.ac.uk/37526/.
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Given the great potential of porous carrier based drug delivery for stabilising the amorphous form of drugs and enhancing dissolution profiles, this thesis centred on investigations into the application of activated carbon (AC) and carbon onion (OLC) as porous carriers for oral delivery, using paracetamol (PA) and ibuprofen (IBU) as model drugs. Initial work was focussed on the toxicity studies of AC followed by preparation and characterisation of drug/AC complex. Results showed that AC is a promising drug carrier with low toxicity, high loading capacity and ability to stabilise amorphous drug. However, loading efficiency and solid state characteristics were different for PA and IBU, whilst the drug release from AC was incomplete in the absence of surfactant. To investigate the factors affecting drug loading, three different loading methods were compared, with solution adsorption followed by centrifugation found to be the optimum method to achieve maximum loading with least crystallinity. Initial drug concentration in the loading solution was also found to influence the loading, where the optimum concentration to achieve maximum loading without any crystallinity differed depending on the chemical nature of the drug. Further, the surface chemistry of AC was modified in order to achieve complete drug release, and results showed that drug release increased with an increase in the surface oxygen content of AC. Also, drug release was found to increase with a decrease in the micropore volume fraction. The second part of the work was focussed on the synthesis and characterisation of OLC, followed by drug loading studies. Results showed that annealing of nano-diamonds (ND) at 1100 oC produced OLC with a diamond core, which is non-toxic. Drug loading studies revealed that loadings achieved were lower than those seen with AC, regardless of drug solubility. Of the both carriers investigated, AC was less expensive and found to be a promising carrier with higher loading capacity and lower toxicity.
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Tsai, Tsung Hui. "Tetrahedral amorphous carbon based field emission display." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620674.
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Piscanec, Stefano. "Raman spectra of graphite, carbon nanotubes, silicon nanowires and amorphous carbon." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614290.
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Khan, Rizwan Uddin Ahmad. "Electronic properties of hydrogenated amorphous carbon thin films." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/844559/.
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This thesis is concerned with the growth, electronic properties and modification of hydrogenated amorphous carbon films of a thickess range of 50-300 nm, which have been deposited using rf plasma-enhanced chemical vapour deposition. These films may be subdivided into two types according to the electrode on which they are grown and the resulting film properties. These are polymer-like amorphous carbon or PAC, and diamond-like amorphous carbon or DAC. PAC possesses a wide optical band gap (2.7 eV), high resistivity (1014 - 10 15 Ocm) and low density of paramagnetic defects (~ 10 17 spins cm-3). The dominant current transport mechanism at room temperature has been observed to be hopping conduction at low electric fields and space-charge-limited current at high electric fields. The addition of nitrogen gas to the plasma to incorporate nitrogen within the film has been shown to move the Fermi level by 1 eV, towards midgap. A mechanism of doping due to the introduction of aromatic nitrogen-containing sites has been postulated. The boron, carbon and nitrogen ion implantation of PAC has resulted in the controllable increase in conductivity from 1015 to 106 O cm as a function of ion dose, from 2 x 1012 to 2 X 1016 ions cm-2. At low ion doses (up to 6 x 1014 ions cm-2) this occurs without any change in band gap; however, at higher doses the band gap collapses as a result of graphitisation. The dependence on the implant ion shows that it is possible to move the Fermi level towards the valence band with the implantation of boron, and towards midgap with the implantation of nitrogen. A hysteresis effect is observed at intermediate ion doses, which is attributed to the trapping of holes resulting in an increase in electron current. Implanting part of the thickness of the film at this ion dose has resulted in rectification, which has not previously been reported for this type of structure in amorphous carbon. DAC has been shown to possess a smaller band gap (0.7 eV), higher density of defects (~ 1020 spins cm-3) and lower resistivity (~ 1013 O cm) than PAC. The room-temperature current transport is governed by band-tail conduction at fields below 105 V cm-1, and the Poole-Frenkel effect at higher fields. The addition of nitrogen of up to 8 at. % has been observed to increase the band gap from 0.7 to 1.0 eV and therefore decrease the magnitude of the Poole-Frenkel conductivity. The Fermi level remains pinned at midgap, however. Therefore, it appears that PAC shows advantages over DAC in terms of future device applications.
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Rusli. "Optical and luminescence properties of hydrogenated amorphous carbon." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326704.
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Wächter, Rolf. "Deposition and characterisation of amorphous hydrogenated carbon films." Thesis, Oxford Brookes University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287760.
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Conway, N. M. J. "Hydrogenated tetrahedrally bonded amorphous carbon for electronic applications." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597911.
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This thesis examines the properties of hydrogenated tetrahedrally bonded amorphous carbon (ta-C:H) grown using a plasma beam source(PBS) and assesses its potential as a semiconductor material for electronic applications. Production of high quality ta-C:H requires optimisation of the deposition conditions and it is therefore of importance to analyse the behaviour of the PBS. It is found that the operation of the PBS agrees with its theoretical description as a capacitively coupled system and the plasma has the required properties to produce ta-C:H. Characterisation of the structural properties confirms the tetrahedral nature of the deposited films. Characterisation of the electronic and optical properties show that ta-C:H is a wide band gap semiconductor which conducts by a thermally activated localised hopping mechanism with a defined activation energy. Measurements of photoconductivity show that ta-C:H grown using methane gas has a photosensitivity greater than in any other form of amorphous carbon. A high density of mid-gap defects will degrade the electronic properties of an amorphous material, however defects can often be passivated by hydrogen. Hydrogen only has a weak passivation effect in ta-C:H and the defect density remains high. Improved passivation is shown to be achieved by post-deposition annealing of ta-C:H, although experimental results suggest that the presence of hydrogen increases localisation of the conduction states. The ability to dope ta-C:H is also important for electronic applications. Strong evidence is presented which suggests that ta-C:H is slightly p-type and can be doped n-type by the addition of nitrogen. This n-type behaviour is further verified by the manufacture of n-type ta-C:H:N thin film transistors (TFTs). The TFTs show a small on/off ratio and require a large turn-on voltage. This is attributed to the relatively high defect density in the mid-gap region, despite its reduction by annealing, illustrating the main problem at present with the use of ta-C:H in device applications.
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Veerasamy, Vijayen S. "Tetrahedral amorphous carbon : deposition, characterisation and electronic properties." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337824.
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Maeng, Sung-Lyul. "Tetraherally bonded amorphous carbon for electronic device applications." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621005.
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Zhao, Zijun. "Tunnelling conduction for resistive switching in amorphous carbon." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/21919.
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Electron transport in amorphous carbon (a-C) with a mixture of sp2 and sp3 hybridization states is treated as a problem in electron tunnelling through barriers. With an optical analogy of "antireflection coating", an unexpected enhancement of transmission is obtained with a positive potential pre-barrier. A finite difference time domain algorithm is used to find the enhancement of transmission through a triangular field emission barrier with a pre-barrier that meets the new condition. Examples are given of available materials to enhance transmission in practical applications including improvement of the efficiency of solar cells. A theory is presented that unifies the description of the optical and electronic properties of a-C dominated by hopping conduction. The theory considers all of the states to be localized to various extents with electronic density of states modeled with Gaussian functions and an energy and temperature dependent ‘hopping mobility’. An example is described to well characterized a-C films prepared by high power impulse magnetron sputtering with a range of sp3 hybridization states. The theory explains the temperature dependence of resistivity and hopping photoconductivity of the films. A link is made between persistent hopping photoconductivity and resistive switching. Resistive switching properties including volatile threshold switching, non-reversible switching, and reversible bipolar switching of a-C are explored using different test structures. An all-carbon device is then fabricated and the structural and electrical characteristics are well described. A mechanism based on the formation of conductive pathways caused by transitions between sp2 and sp3 hybridization states is proposed and the current-voltage characteristics were modeled. The switching was attributed to reversible electric field induced alteration of the hybridization states of carbon atoms. A proposal for carbon-based hardware neuromorphic computing platform is described.
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Abbas, Gamal A. W. "A spectroscopic study of modified tetrahedral amorphous carbon (ta-C) and hydrogenated amorphous carbon (a-C:H) films for diffusion barrier applications." Thesis, University of Ulster, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412130.
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Godwin, Paul D. "Structure and properties of diamond-like carbon." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360316.
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Miyajima, Yoji. "Electronic properties of pulsed laser deposited amorphous carbon and carbon nitride thin films." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843244/.
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This thesis is concerned with the electrical properties of the disordered amorphous material, amorphous carbon and carbon nitride films. At first, hydrogenated amorphous carbon was deposited using rf plasma enhanced chemical vapour deposition with methane as a precursor. Changing the deposition parameter, such as the input power results in the negative self bias modification and thus changes in the properties of the deposited film. The hydrogen condition in the deposition chamber is important for the growth of these films. With the demonstration of an achieve electronic device, a resonance tunnel diode, was reported using pulsed laser deposition; pulsed laser deposited amorphous carbon and carbon nitride thin films were studied. To understand the electrical properties of these films, a wide range of measurements were performed. The surface morphology was examined using atomic force microscopy and scanning tunnelling microscopy. The microstructure was investigated using electron energy loss spectroscopy giving data on the sp2 fraction, density, nitrogen content and Raman spectroscopy showed the degree of sp2 clustering. The band structure was investigated using electron energy loss spectroscopy, scarnning tunnelling spectroscopy and ultraviolet photoelectron spectroscopy, giving information on the density of empty conduction band states, close to the Fermi level and the occupied valence band states. The joint density of states was also measured by ultraviolet-visible-infrared optical transmittance, spectroscopic ellipsometry and Photothermal deflection spectroscopy. Electrical characterisations were carried out using both sandwich and coplanar structures. Pulsed laser annealing of amorphous carbon films was also studied, and the change on the surface morphology, microstructural and electrical properties studied. The conduction mechanism in amorphous carbon films at high electric fields was found to be based on classical Poole-Frenkel conduction, and the dielectric constants estimated from the model were found to be consistent with optical measurements. The neutral trapping centres were postulated to be localised sp2 sites below the conduction band according the analysis of the total band structure. Low field conduction in amorphous carbon films were thought to be controlled by band tail hopping through localised sp2 sites. Laser annealing shows the increase of the number of the sp2 sites which increase the conductivity of the film. However, the sp2 clustering does not necessarily increase the conductivity of the film. The optical band gap in high stress amorphous carbon films can be smaller than the other reports, as a bandtail exists in the bandgap which contributes to the hopping and Poole- Frenkel conduction process. The influence to the nitrogen atoms incorporated to laser deposited amorphous carbon nitride films was also studied. It was found that the nitrogen gas background pressure in the deposition chamber strongly affects the properties of the films. It was demonstrated that a higher nitrogen pressure does not always give rise to higher nitrogen content in the films. Higher nitrogen pressure reduces the velocity of the incident carbon species ablated by the laser, and less dense (less stress) films were deposited. Consequently, the conductivity of the film was reduced. However, the conduction mechanism appears still to be similar to that of amorphous carbon. The analysis of the change in the band structure due to the incorporation of the nitrogen atoms supports the analysis. Thus, the entire band structure of amorphous carbon was linked to the electrical conduction mechanism at both high and low electric fields, including the effect of nitrogen atom incorporation, and pulsed laser annealing. In this thesis we report the highest field effect mobility of a-C and a-CNx films ever reported in the literature of 0.01-0.02 cm2/Vs. This mobility is obtained due to the very high electric field that can be applied to our devices.
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Jiang, Yucheng, and 姜昱丞. "Magnetoresistance, photoconductivity and strain effect in the system of magnetically doped amorphous carbon." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208021.
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Tsai, Kun-Chao. "Investigation of micro-mechanical applications of amorphous carbon films." Thesis, University of Ulster, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288900.
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Bayley, P. A. "Electronic characterisation of amorphous silicon-carbon alloy thin films." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636060.
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Excess electron and hole drift mobilities in hydrogenated amorphous silicon-carbon alloy thin films have been investigated using the time-of-flight technique. A detailed study of the temperature and electric field dependence of these parameters has been carried out. This has permitted the computation of the energy distributions of conduction and valence band tail localised states as a function of carbon concentration in the films. It is apparent from these data that increased carbon incorporation is associated with an increase in the total number of both the conduction and valence band tail states. This is supported by the experimental behaviour of the pre-transit currents. The present range of materials were produced by conventional low power radio frequency glow discharge of silane and methane. Typical carbon contents are below 10at.% and optical measurements show that the samples have optical energy gaps Eg up to 2.0eV. Time-of-flight charge collection experiments have been performed to investigate the free carrier mobility-lifetime products as a function of carbon concentration in the films. Results show a considerable decrease in this parameter with increasing carbon content. This is likely to be primarily associated with an increase in density of recombination centres in the films. The density of localised states in the materials have also been computed using a Fourier transformation of transient photo-current data. This reveals the increase in density of the conduction band tail states, as detected using the drift mobility analysis, but also reveals an increase in density and energetic broadening of the deep state distribution as carbon content is increased. This is consistent with the reduced carrier lifetimes inferred by the charge collection experiments. Combining the present data with localised state energy distributions measured using other techniques, we are able to illustrate the effect of carbon alloying on the entire localised state population. Preliminary transient photoconductivity results for glow discharge deposited diamond films are also reported.
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Paul, Shashi. "Growth, characterisation and electronic applications of amorphous hydrogenated carbon." Thesis, De Montfort University, 2000. http://hdl.handle.net/2086/4176.
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Chen, Hsiung. "Preparation, properties, and structure of hydrogenated amorphous carbon films." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054566593.
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Manzoor, M. U., Cristina-Luminita Tuinea-Bobe, F. McKavanagh, C. P. Byrne, D. Dixon, P. D. Maguire, and P. Lemoine. "Amorphous carbon interlayers for gold on elastomer stretchable conductors." Journal of Physics D: Applied Physics, 2011. http://hdl.handle.net/10454/17072.
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NoGold on polydimethylsiloxane (PDMS) stretchable conductors were prepared using a novel approach by interlacing an hydrogenated amorphous carbon (a-C : H) layer between the deposited metal layer and the elastomer. AFM analysis of the a-C : H film surface before gold deposition shows nanoscale buckling, the corresponding increase in specific surface area corresponds to a strain compensation for the first 4–6% of bi-axial tensile loading. Without this interlayer, the deposited gold films show much smaller and uni-directional ripples as well as more cracks and delaminations. With a-C : H interlayer, the initial electrical resistivity of the metal film decreases markedly (280-fold decrease to 8 × 10−6 Ω cm). This is not due to conduction within the carbon interlayer; both a-C : H/PDMS and PDMS substrates are electrically insulating. Upon cyclic tensile loading, both films become more resistive, but return to their initial state after 20 tensile cycles up to 60% strain. Profiling experiments using secondary ion mass spectroscopy and x-ray photoelectron spectroscopy indicate that the a-C : H layer intermixes with the PDMS, resulting in a graded layer of decreasing stiffness. We believe that both this graded layer and the surface buckling contribute to the observed improvement in the electrical performance of these stretchable conductors.
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Oliveira, Junior Myriano Henriques de. "Propriedades ópticas, mecânicas e estruturais de filmes de carbono amorfo." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277831.
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Orientador: Francisco das Chagas MarquesTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Neste trabalho desenvolvemos um sistema de deposição de filmes finos pela técnica de arco catódico filtrado (FCVA- Filtered Cathodic Vacuum Arc), que possibilita o desenvolvimento de ligas metálicas e, sobretudo, a deposição de filmes de carbono amorfo altamente tetraédrico. Utilizando este sistema desenvolvemos filmes de carbono amorfo (a-C) com elevada dureza (estimado em cerca de 50 a 60GPa) e alta concentração de ligações sp3 C-C em função da polarização do substrato. Estudamos as propriedades ópticas, mecânicas (stress e dureza), estruturais (Raman e RBS) e a estabilidade térmica (efusão de gases) destes filmes em função da energia de deposição. Também desenvolvemos e caracterizamos filmes de carbono crescidos por FCVA assistido por um feixe de íons secundário de Ar e Kr com diferentes energias, onde analisamos os efeitos da energia deste feixe sobre as propriedades físicas do material resultante. Além das estruturas de carbono intrínseco realizamos um estudo sobre filmes de carbono amorfo hidrogenado depositados por PECVD (plasma enhanced chemical vapor deposition) com diferentes tensões de bias (de 60 à 550V) e atmosferas mistas de CH4/Kr, onde variamos a pressão parcial deste gás nobre entre 0 e 50%. Estudamos a influência deste gás nobre sobre as propriedades estruturais do material assim como a forma como os átomos deste elemento se distribuem dentro da rede amorfa. Esta última análise foi baseada em estudos conduzidos a partir da absorção de raios-x na borda K do átomo de criptônio, onde verificamos a aglomeração destes átomos na forma de estruturas solidas. Também investigamos os processos de transformações estruturais ocorridas em estruturas a-C:H e ta-C com a temperatura baseadas na efusão de gases. Para este estudo construímos um sistema que funciona em ultra-alto vácuo, com temperatura controlada variando de ambiente até cerca de 1000 graus. Os estudos sobre as propriedades estruturais foram baseados, sobretudo, em medidas de espectroscopia de espalhamento Raman com radiação de excitação na região do visível e do ultravioleta, o que possibilita a obtenção de informações mais detalhadas sobre a forma como os átomos sp2 e sp3 distribuem-se no material. Por fim, exploramos o potencial de aplicação de três tipos de carbono amorfo; tipo polimérico (PLC), tipo diamante (DLC) e tetraédrico (ta-C) como monocamadas antirefletoras para células solares de silício cristalino e comparamos com o desempenho obtido com camadas fabricadas com materiais usualmente empregados na indústria para tal aplicação. Os resultados mostraram que filmes de carbono amorfo podem ser utilizados como camada anti-refletora. Os filmes de carbono tipo polimérico apresentaram resultados muito semelhantes aos obtidos com camadas convencionais de dióxido de estanho
Abstract: In this work we designed, manufactured and characterized a Filtered Cathodic Vacuum Arc (FCVA) deposition system. This technique is usually applied in the preparation of metallic alloys and highly sp3 - hybridized amorphous carbon thin films. By using this system we prepared a series of amorphous carbon films (a-C) with high hardness (up to ~60GPa) and high concentration of sp3 C-C bonds varying the deposition energy of the C+ ions. Mechanical (hardness and intrinsic stress) and structural (Raman, RBS and gas effusion) were investigated. Another series of a-C was developed by FCVA, but using an assisted beam of Ar or Kr as a function of the ion energy. The main purpose of this work is to understand of the effects of the bombardment of an energetic ion beam on the physical properties of the films. Another study performed on hydrogenated amorphous carbon films (a-C:H) were carried out on samples deposited by plasma enhanced chemical vapor deposition (PECVD). The films were prepared with different self-bias, varying from 60 up to 550V, and different mixed atmospheres of methane and krypton gases, varying the partial pressure of krypton from 0 to 50%. Films prepared at low bias are polymeric-like (PLC), while films prepared at high bias are diamond-like (DLC). We had performed investigations on the influence of this noble gas on the structural properties of the a-C:H films and how the Kr atoms are arranged within the amorphous matrix. The distribution of Kr atoms was studied mainly by x-ray absorption on the krypton absorption K-edge. Due to the absence of EXAFS oscillations the spectra were interpreted using the XANES region, which gave us evidences of clustering of Kr atoms. The processes involved in the a-C:H nd ta-C structural transformations during the thermal annealing were analyzed by means of thermal gas effusion measurements (using a quadrupole spectrometer) in a system developed in our laboratory. Raman scattering spectroscopy measurements were carried out with excitation radiation in the visible and ultraviolet ranges. This choice is justified due to the more detailed information obtained by multiwavelength Raman spectroscopy on the distribution of sp2and sp3sites within the amorphous carbon matrix. Finally, we had evaluated the possibility of the application of three types of amorphous carbon structures, the diamond-like and polymeric-like carbon, and the ta-C as antireflective coating on crystalline silicon solar cells. We observed that all amorphous carbon structures (DLC, PLC and ta-C) increase the short-circuit current of the solar cells. In the case of PLC films, the result is comparable to that obtained with conventional antireflective coating such as tin dioxide (SnO2)
Doutorado
Física da Matéria Condensada
Doutor em Ciências
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Rahman, Md Anisur. "Tetrahedral amorphous carbon (ta-C, ta-C:N) and hydrogenated amorphous carbon (a-C:H) thin films : Studies of deposition, residual stress and surface energy." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520545.
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El-Hossary, F. M. "Thin-film amorphous carbon prepared by plasma chemical deposition processes." Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381486.
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Manage, Dammika P. "Structural and optical characterization of hydrogenated amorphous carbon thin films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0005/NQ41228.pdf.
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Lee, Deok-Hyung (Doug). "Mechanisms of surface hardness enhancement in ion-implanted amorphous carbon." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19639.
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White, Andrew James. "Photon-enhanced chemical vapour deposition of amorphous carbon thin films." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320045.
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HOLGADO, DANNY PILAR ARAUCANO. "STUDY OF THE TRIBOLOGICAL PROPERTIES OF FLUORINATED AMORPHOUS CARBON FILMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19910@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Este trabalho teve como objetivos o estudo das modificações nas propriedades de filmes de carbono amorfo hidrogenado (a-C:H) através do tratamento da sua superfície com plasma de tetrafluoreto de carbono (CF4) e Argônio e a deposição e estudo das propriedades tribológicas de filmes de carbono amorfo fluorado e hidrogenado (a-C:F:H) sobre substrato de aço inoxidável 316L. A primeira parte da tese descreve a funcionalização por plasma da superfície com flúor de filmes previamente depositados de a-C:H sobre silício cristalino 100 pela técnica da deposição química na fase vapor assistido por plasma PECVD. Esta funcionalização foi feita pelo emprego de plasma de uma mistura dos gases CF4 e Argônio em diferentes proporções. Estes filmes tiveram a sua superfície analisada por espectroscopia de fotoelétrons, microscopia de força atômica e tiveram a sua energia superficial avaliadas por medidas de ângulo de contato de três diferentes líquidos (água deionizada, glicerol e bromonaftaleno). A funcionalização com Flúor tornou a superfície superhidrofóbica, atingindo valores em torno de 140 graus. Na segunda parte da tese descrevemos com sucesso a deposição por PECVD de filmes de carbono amorfo fluorados sobre substratos de aço inoxidável 316L. Para melhorar a adesão, os substratos foram submetidos a tratamento com nitretação e carbonitretação por plasma e a posterior deposição de um filme de titânio e de a-C:H. Nestes filmes foram realizadas medidas de microscopia de força atômica, dureza, espectroscopia de fotoelétrons e tribometria para determinar o coeficiente de atrito e resistência ao desgaste mecânico. Os resultados obtidos mostraram que a incorporação de CF4, produz filmes com propriedades semelhantes às propriedades do Teflon. Obtivemos filmes com dureza em torno de 11Gpa, mais duro que o aço inoxidável 316L, cuja dureza é de aproximadamente 4,5 GPa, porém menor que a medida em aço nitretado. Com relação ao coeficiente de atrito, o filme de a-C:F:H apresentou uma redução significativa em relação ao aço e ao aço nitretado. As medidas de tribometria também mostraram que o filme ficou bem aderido e apresenta boa resistência ao desgaste mecânico, resistindo a centenas de ciclos com a ponta do tribometro arrastando sobre a superfície com forças aplicadas de 10N. Como resultado conseguimos depositar filmes sobre aço inoxidável 316L com baixo coeficiente de atrito, dureza elevada e boa resistência ao desgaste mecânico.
This work aimed to the study of the modifications of the properties of carbon amorphous hydrogenated films (a-C:H) trough the treatment of the surface film with plasma of carbon tetra fluoride (CF4) and Argon. Another object has been the study of the tribological properties of carbon amorphous fluorinated and hydrogenated (a-C:F:H) deposited on substrates of stainless steel 316L. The first part of the these describes the functionalization by plasma of the surfaces with fluorine of films previously deposited of a-C:H on crystalline silicon 100 by the technique of plasma enhanced chemical vapor deposition PECVD. This functionalization was made by the use of plasma of a mixture of CF4 and Argon gases in different proportions. The films had their surfaces analyzed by photoelectron spectroscopy, atomic force microscopy and their surface energies calculates by measurement of the angle contact of three different liquids (water, glycerol and bromonaphthalene). The functionalization with Fluorine made the surface super hydrophobic, reaching values for the contact angle around 140 degrees. In the second part of the these we describe the successful deposition by PECVD of films of carbon amorphous fluorinated on stainless steel 316L. In order to improve the adhesion, the substrates were submitted to treatment with nitriding and carbonitriding by plasma and the subsequent deposition of a film of titanium and a-C:H. In these films were realized measurements of atomic force microscopy, hardness, photoelectron spectroscopy and tribometry to determine the friction coefficient and the resistance to mechanical wastage. The results obtained showed that an incorporation of CF4, produces films with properties similar to teflon properties. We obtained films with hardness around 11 Gpa, harder than stainless steel 316L, whose hardness is approximately 4,5 Gpa, but smaller than the measure in nitrated steel. In relation to the friction coefficient, the film of a-C:F:H presented a significant reduction in relation to the steel and nitrated steel. The tribometry measurements also showed that the film was well adhered and present good resistance to mechanical wear, resisting to hundreds of cycles with the point of the tribometry dragging on the surface with applied force of 10N. As result we get to deposit films on stainless steel 316L with low friction coefficient, elevated hardness and good resistance to mechanical wear.
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Cooper, Jack. "Amorphous carbon coating systems for pressurised water reactor tribological applications." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/22484/.
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Gammon, W. Jason. "Chemical bonding in hard and elastic amorphous carbon-nitride films." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539623423.
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In this study, the chemical bonding in hard and elastic amorphous carbon nitride (a-CNx) films is investigated with x-ray photoelectron spectroscopy (XPS) and 15N, 13C, and 1H nuclear magnetic resonance (NMR) spectroscopy. The films were deposited by DC Magnetron sputtering in a pure nitrogen discharge on Si(001) substrates at 300--400??C. Nanoindentation measurements reveal an elastic modulus of ∼50 GPa and a hardness of ∼5 GPa, thus confirming our films are highly elastic but resist plastic deformation.;Our 13C NMR study demonstrates the absence of sp 3-bonded carbon in this material. Collectively, our N(1s) XPS, 13C NMR, and 15N NMR data suggest a film-bonding model that has an aromatic carbon structure with sp2-hybridized nitrogen incorporated in heterocyclic rings. We demonstrate that the nitrogen bonding is predominantly in configurations similar to those in pyridine and pyrrole. In addition, the data indicate that the a-CNx films prepared for this study have low hydrogen content, but are hydrophilic. Specifically, results from 15N and 13C cross polarization (CP) and 1H magic angle spinning (MAS) NMR experiments suggest that nitrogen sites are susceptible to protonation from water absorbed during sample preparation for the NMR experiments. The sensitivity of the surface of a-CNx to water absorption may impact tribological applications for this material.;In accord with our XPS and NMR spectroscopic studies on a-CN x films, we propose a film-structure model consisting of buckled graphitic planes that are cross-linked together by sp2 hybridized carbons. The curvature and cross-linking is attributed to a type of compound defect, which is formed by placing a pentagon next to single-atom vacancy in a graphite layer. Our proposed film structure is called the pentagon-with-vacancy-defect (5VD) model. Using Hartree-Fock calculations, we show that the 5VD, film-structure model is compatible with our XPS, NMR, and nanoindentation measurements and with previous transmission electron microscopy (TEM) and computational work.
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Dawson, Janet Caroline. "The electronic properties of granular and amorphous materials." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318097.
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Pritchett, Merry. "Adherence/Diffusion Barrier Layers for Copper Metallization: Amorphous Carbon:Silicon Polymerized Films." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4493/.
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Semiconductor circuitry feature miniaturization continues in response to Moore 's Law pushing the limits of aluminum and forcing the transition to Cu due to its lower resistivity and electromigration. Copper diffuses into silicon dioxide under thermal and electrical stresses, requiring the use of barriers to inhibit diffusion, adding to the insulator thickness and delay time, or replacement of SiO2 with new insulator materials that can inhibit diffusion while enabling Cu wetting. This study proposes modified amorphous silicon carbon hydrogen (a-Si:C:H) films as possible diffusion barriers and replacements for SiO2 between metal levels, interlevel dielectric (ILD), or between metal lines (IMD), based upon the diffusion inhibition of previous a-Si:C:H species expected lower dielectric constants, acceptable thermal conductivity. Vinyltrimethylsilane (VTMS) precursor was condensed on a titanium substrate at 90 K and bombarded with electron beams to induce crosslinking and form polymerized a-Si:C:H films. Modifications of the films with hydroxyl and nitrogen was accomplished by dosing the condensed VTMS with water or ammonia before electron bombardment producing a-Si:C:H/OH and a-Si:C:H/N and a-Si:C:H/OH/N polymerized films in expectation of developing films that would inhibit copper diffusion and promote Cu adherence, wetting, on the film surface. X-ray Photoelectron Spectroscopy was used to characterize Cu metallization of these a-Si:C:H films. XPS revealed substantial Cu wetting of a-Si:C:H/OH and a-Si:C:H/OH/N films and some wetting of a-Si:C:H/N films, and similar Cu diffusion inhibition to 800 K by all of the a-:S:C:H films. These findings suggest the possible use of a-Si:C:H films as ILD and IMD materials, with the possibility of further tailoring a-Si:C:H films to meet future device requirements.
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Millar, Mark A. W. "Plasma deposited silicon incorporated amorphous carbon thin films for automotive applications." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535144.
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Munindradasa, Dedimuni Amith Indika. "Electrical and optical properties of nitrogenated : hydrogenated : amorphous carbon thin films." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397394.
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The electronic and optical properties of hydrogenated amorphous carbon (a-C: H) and nitrogenated : hydrogenated amorphous carbon (a-C: H: N), deposited using inductively coupled plasma enhanced chemical vapour deposition (ICPECVD) and helicon wave excited plasma enhanced chemical vapour deposition (HWPECVD) are discussed in this thesis. The design and the implementation of the helicon wave excited plasma system is also presented. The capacitance voltage (C-V) characteristics of heterojunctions formed by depositing a-C: H: N on Si, show that almost ideal interface behaviour can be accomplished using ICPECVD for optimised plasma conditions. The highest frequency response, known to date for a-C, 13MHz, is also reported. The photoluminescence (PL) studies are carried out to investigate the influence of nitrogen in a-C: H: N. The nitrogen and the optical band gap dependencies of PL indicated the existence of N associated recombination centres. A twin recombination mechanism at localised tails and N associated centres is suggested to describe the observed behaviour. The capability of selective energy transitions in a helicon wave plasma as predicted theoretically is successfully demonstrated for N2 plasma. The passivation of high power electronic devices and the electron field emission are presented as potential areas where a-C: H and a-C: H: N perform successfully
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Philipp, Peter. "Phase transformation in tetrahedral amorphous carbon by focused ion beam irradiation." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-136547.
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Ion irradiation of tetrahedral amorphous carbon (ta-C) thin films induces a carbon phase transformation from the electrically insulating sp3 hybridization into the conducting sp2 hybridization. In this work, a detailed study on the electrical resistivity and the microstructure of areas, irradiated with several ion species at 30 keV energy is presented. Continuous ion bombardment yields a drastic drop of the resistivity as well as significant structural modifications of the evolving sp2 carbon phase. It is shown that the resistivity lowering can be attributed to the degree of graphitization in the film. Furthermore, the structural ordering processes are correlated with the ion deposited energy density. It is therefore revealed that the ion-induced phase transformation in ta-C films is a combination of sp3-to-sp2 conversion of carbon atoms and ion-induced ordering of the microstructure into a more graphite-like arrangement. All experiments were done with focused ion beam (FIB) systems by applying FIB lithography of electrical van-der-Pauw test structures. FIB lithography on ta-C layers is presented as a fast and easy technique for the preparation of electrically active micro- and nanostructures in an insulating carbon matrix.
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Burke, Theresa Mary. "An X-ray and neutron scattering study of amorphous hydrogenated carbon." Thesis, University of Kent, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240132.
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Ibrahim, Faridah. "Photo-oxidation of amorphous silicon carbon alloys preparation and mechanistic study." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1489.
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Arena, Claudia. "Local properties of tetrahedral amorphous carbon investigated by scanning tunnelling microscopy." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624394.
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Grigonis, A., A. Micko, A. Medvid, R. Zabels, Z. Rutkuniene, and V. Vinciunaite. "IR, VIS, and UV laser light irradiation of amorphous carbon films." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20640.
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Diaz, Javier. "Study of amorphous carbon thin films grown by pulsed laser deposition." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10015.
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Le but de cette these est l'etude des parametres physiques qui font varier les proprietes electroniques et mecaniques des couches minces de carbone amorphe (a-c) evaporees par la technique de deposition par laser pulse (pld). Tout d'abord, on a fait des experiences pour connaitre le systeme experimental: on a etudie la composition du materiau evapore et la cinetique de deposition des particules sur la surface de si (111) 7x7. Cette derniere a ete observe a l'echelle atomique avec un microscope a effet tunnel dans l'ultra vide. Dans une deuxieme partie, on a caracterise les depots de a-c. Ces films ont une densite entre 2. 45 g/cm#3 et 2. 8 g/cm#3 et une durete jusqu'a 50 gpa. Ils sont semiconducteurs avec un gap optique de 0. 3 ev et une resistivite electrique de 10#5 cm. Ces proprietes sont degradees si l'energie cinetique des particules evaporees est diminuee. L'analyse physico-chimique de ces couches minces a ete faite en utilisant les spectroscopies de photoemission (xps et ups), d'absorption des rayons x (nexafs) et raman. Cette analyse revele que ces couches sont constituees par des atomes de carbone hybrides sp#2 et sp#3. La proportion des liaisons sp#3 par rapport aux liaisons sp#2 est de 40% pour les couches dures (45 gpa) et 25% pour les moins dures (22 gpa). Les resultats nexafs obtenus en detection d'electron et en fluorescence semblent indiquer un gradient de densite du materiau, celle-ci augmentant de la surface vers le volume. Finalement, la similitude observee entre les spectres raman de films de a-c avec des duretes semblables mais des gap optiques radicalement differents indiquent que la spectroscopie raman est plus sensible a l'organisation structurale qu'aux proprietes electroniques des depots de a-c
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Stephan, Uwe. "Theoretical methods and results for electronic-structure investigations of amorphous carbon." [S.l. : s.n.], 1996. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10324488.
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Jonsen, Daniel Everett. "Experimental and Computational Studies of Carbon Sputtering with Application to Deposition of Tetrahedrally Bonded Amorphous Carbon Films." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010805-194422.
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JONSEN, DANIEL EVERETT. Experimental and Computational Studies of Carbon Sputtering with Application to Deposition of Tetrahedrally Bonded Amorphous Carbon Films. (Under the direction of Dr. Jerome J. Cuomo.)
In this work, amorphous carbon films are deposited on various substrates by ion beam sputtering of a graphite target. In addition, computational studies of the carbon sputtering process are performed using a molecular dynamics simulation program. In both cases, several process parameters are varied with the intent to find the optimum conditions for the sputter deposition of amorphous carbon films of high sp content amorphous carbon films.
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Li, Yuting. "Simulations and Electronic Structure of Disordered Silicon and Carbon Materials." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1395410498.
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Zehnder, Thomas. "Deposition of silicon carbide and amorphous carbon films by pulsed laser deposition /." Bern : [s.n.], 1995. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Lee, Sang Joon. "Structure and Interaction Energies of Kr Atoms Adsorbed on Graphitic Amorphous Carbon." DigitalCommons@USU, 1995. https://digitalcommons.usu.edu/etd/2091.
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The physisorption of Kr on graphitic amorphous carbon (g-C) has been investigated using a statistical approach. The interaction energy calculation process (i) established a structural model of g-C and (ii) determined the adsorbate-adsorbate and the adsorbate-substrate interaction potentials on g-C.
The structural model of g-C was divided into three regions. For the interaction potential between a Kr atom and a carbon atom the short and medium range order of g-C was described with a discrete medium model based on three ring clusters using ring statistics from Beeman's continuous random network C1120 model of g-C. For the intermediate distance region, Beeman's radial distribution function was used to model g-C. A homogenous and isotropic continuous medium model was used at large distances.
The Kr-Kr and Kr-g-C interaction potentials used for Kr on g-C, which are pair-wise Lennard-Jones 6-12 potentials, are similar to Kr on graphite potentials. the validity of the model for g-C and the potentials were verified though calculations for Kr on graphite. Results compared favorably with recent literature values.
The interaction energy calculation results for Kr on a g-C substrate assert that (i) Kr adlayers will form on g-C, (ii) the structure of the Kr adlayer is governed by the substrate corrugation at low coverage and by the Kr-Kr interaction at high coverage, and (iii) there is no direct relation between the structure of Kr adlayers on g-C and those on graphite. The average binding energy of Kr on g-C is comparable with that on graphite, but the corrugation of g-C is perhaps six times that of a graphite substrate. The wrinkling of the g-C surface, due to the presence of a distribution of 5-, 6-, and 7- membered rings, is responsible for this large corrugation of the g-C substrate.