CVD diamond nucleation enhanced by ultrasonic pretreatment using diamond and mixture of diamond and TaC powders

摘要

Effects of ultrasonic pretreatment on chemical vapor deposition (CVD) diamond nucleation on Si substrates were systematically studied. Pure 1.5-40 mum-diamond powder and mixtures of 1.5-5 mum-diamond as well as 5-20 mum-Tantalum Carbide (TaC) powder were used in ultrasonic pretreatment. The root-mean-square (Rms) surface roughness of the pretreated substrates, residual diamond and TaC powders left on the substrates were examined using atomic force microscopy (AFM), Raman spectroscopy and X-ray diffraction (XRD), respectively. It was observed that the Rms surface roughness increases with increasing diamond or TaC powder size, and there is some diamond or TaC powder left on the substrates after ultrasonic pretreatment. Diamond films were deposited using microwave plasma chemical vapor deposition (MPCVD) technique and characterized by field emission scanning electron microscop (FE-SEM). It was found that CVD diamond nucleation density strongly depends on particle size of diamond or TaC powder used, the nucleation density increases with increasing diamond or TaC powder size. A mixture of diamond and TaC powders enhances CVD diamond nucleation much more significantly than that of pure diamond powder. A mixture of 1.5 mum-diamond and 20 mum-TaC powders has an equivalent nucleation enhancement efficiency, which could be caused by pure 40 mum-diamond powder.