Research On The Fabrication,Growth Mechanism And Anti-Reflection Performance Of Diamond-Like Carbon Films

Diamond-like carbon(DLC)films have attracted great attention in recent years.Due to their attractive properties,they are considered as important materials for electronic,optical,and wear-protection applications.Chemical inertness,high hardness,low friction,and high thermal conductivity are all similar to those of diamond because of the sp3-type hybrid C bonds they possess.Chemical vapor deposition and physical vapor deposition technologies for the preparation of DLC thin films are the hotspots of current research and have aroused a great interest.In this thesis,a plasma enhanced chemical vapor deposition system was used to inject the methane(CH4)precursor into the argon(Ar)plasma.The plasma emission spectra were studied in situ using light emission spectroscopy,and then,the DLC films were grown on quartz glass and silicon wafer substrates,respectively.CH4 was decomposed to produce C2 species dominantly through the electron impact,dehydrogenation and energy transfer from the excited state argon atoms,and simultaneously hydrocarbons containing C2 and less number of hydrogens such as C2H2 and/or C2H were formed during the dissociation process.By injecting CH4 into the Ar plasma,the light emission characteristics of Ar-CH4 plasma under different discharge powers,different reaction pressures,and different CH4 flow rates were compared The dehydrogenation and energy transfer process of CH4 were analyzed to investigate different dissociation channels of CH4.Under the same conditions,the temperature of the Ar plasma was higher than that of the Ar-CH4 plasma,indicating that the endothermic reaction was dominant in the Ar-CH4 plasma.The formation mechanism of DLC films was inferred and analyzed according to different types of radicals generatedby the cracking of CH4 under the glow discharge.The growth process of DLC films was affected by several process parameters such as the deposition time,the plasma discharge power,the reaction pressure,the CH4 flow rate,and the substrate temperature.In this thesis,the optical properties and corresponding Raman structure and surface morphology of the synthesised DLC films were investigated under different deposition times,different plasma discharge powers,different CH4 flow rates,and different substrate temperatures,respectively.It was shown that,when the plasma discharge power was 100 W,the CH4 flow rate was 60 scem,and the substrate temperature was 100?,the synthesised DLC film had a high diamond(sp3 C-C)phase,transmittance of 95%,a low surface reflectivity of approximately 14%,as well as a uniform and dense texture.Subsequently,the DLC films with different thicknesses were grown on the surface of crystalline silicon solar cells as anti-reflection coatings.The solar cell current-voltage characteristic testing system was used to study the change of solar cell performance parameters,i.e.,Jsc,Voc,FF and ?.After deposition of a 20-minute-thick DLC film on the surface of a silicon solar cell,the efficiency of the cell increased from 4.12%to 5.2%.