Preparation Of Large Area Thick Diamond Films

The potential application of the diamond film in various fields has surprisingly increased in recent years,due to its excellent mechanical,electrical , thermal and optical properties. For optimizing the deposition technology of large area thick diamond film and preparing the diamond films which satisfy the need of different fields. In this thesis, the deposition technology of large area thick diamond film and high quality diamond films has been studied,and discuss the effects of nitrogen flow rate on diamond growth properties. 1)The growth properties and deposition parameters of large area thick diamond films are studied. At the process of large area thick diamond films deposition, the diamond films thickness and quality are not uniform which has been caused by the non-uniform of the glow discharge. For improving the glow discharge state and decreasing the non-uniform of substrate temperature,the parallel degree between the filament and substrate plane must be adjusted carefully,and the exhalation degree of the glow discharge should be improved. In addition, for the better touch of the substrate and cushion, they must be adjusted carefully. It has been found that frequent variation of substrate temperature and the non-uniform of substrate temperature are the main reasons of the micro-crack generation. SEM shows that the growth properties of diamond films present columnar figure. In this thesis, by the systemic technology experiment ,the optimized technology parameters are given, and the diamond films with a diameter of 100mm have been successfully manufactured. 2) The Nitrogen concentration in the diamond films deposition environment has been changed by adding nitrogen. The effects of nitrogen on diamond film deposition have been studied. The effects of nitrogen flow rate on diamond growth rate have been studied. It is found that the diamond deposition rate depends greatly on the nitrogen flow rate. The experiment results show that the diamond film growth rate increased when nitrogen flow rate is lower (～4sccm),it is decreased when nitrogen flow rate is higher at higher substrate temperature. The growth rate decreases with the increase of nitrogen flow rate at the lower substrate temperature. Raman spectrum results indicate that:at the higher substrate temperature,Raman peak intensity at 1332 cm-1 decrease with thenitrogen flow rate increase. But the Raman peak intensity at 1350 cm-1 and 1550 cm-1 increase with the nitrogen flow rate increase. At the lower substrate temperature, all samples reveal a sharp intrinsic Raman peak at 1332 cm-1, which indicates that all samples have good quality. The Raman peak at 2060cm-1and 3790cm-1 is obviouse, so it is revealed that [N-V]0 and [N-V]-1 is contained in diamond films. Comparing the SEM pictures of the diamond films, the morphology of the diamond films have changed obviously with the change of nitrogen flow rate. At the higher substrate temperature, SEM results shows that the morphology in "cauliflower-like"contained diamond (100) faces when nitrogen flow rate is 8sccm, the amount of (100) faces on surface of the "cauliflower-like"is decreased obviously when nitrogen flow rate is increased further. The diamond film quality becomes poor; while,at the lower substrate temperature,the figure of the grains become clear and integrated. XPS results show that the bond structure of the surface layer of diamond films change obviously.sp3C—C bond decrease with the nitrogen flow rate increase, and sp2C—N bond increase with the nitrogen flow rate increase.