Low temperature synthesis of nanocrystalline diamond films deposited by microwave CVD

Nanocrystalline diamond thin films were grown on silicon substrates at 480 ℃ using methanol and hydrogen mixtures in microwave plasma chemical vapor deposition(MPCVD).Effect of the methanol concentration and deposition temperature on morphology of diamond films was investigated.The evidence of nanocrystallinity and purity was obtained by characterizing the samples with a combination of Raman spectroscopy,atomic force microscopy(AFM) and scanning tunneling microscopy(STM).The results show that the high quality nanocrystalline diamond film can be deposited on a 50 mm diameter Si substrate by increasing the methanol concentration and reducing the deposition temperature.The grain size was observed to be approximately 10~20 nm by STM.The mechanism of deposition high quality nanocrystalline diamond thin film at low temperature was also presented.