Diamond nucleation and growth under very low-pressure conditions

The synthesis of thin diamond films using various chemical vapor deposition methods has received significant attention in recent years due to the: uni que characteristic of diamond, which make it an attractive candidate for a wide range of applications. In order to grow diamond epitaxially, the prope r control of diamond nucleation on mirror-polished Si is essential. Adding the negative bias voltage to the substrate is the most popular method. This paper has proposed a new method to greatly enhance the nuclear density. Un der very low pressure (1 torr), the high-density nucleation of diamond is a chieved on mirror-polished silicon in a hot-filament chemical vapor deposit ion (HFCVD). Scanning electron microscopy has demonstrated that the nuclear density can be as high as 10(10)-10(11) cm(-2). Raman spectra of the sampl e have shown a dominant diamond characteristic peak at 1332 cm(-1) The pres sure effect has been discussed in detail and it has been shown that the ver y low pressure is a very effective means to nucleate and grow diamond films on mirror-polished silicon. Extraordinary pure hydrogen (purity = 99.9999% ) was used as the source. Compared with the highly pure hydrogen (purity = 99.99%), we found that the density of nucleation was greatly increased. The residual oxygen in the hydrogen displayed a very obvious negative effect o n the nucleation of diamond, although it can accelerate the growth of diamo nd. Based on these results, it was suggested that the enhanced nucleation a t very low pressure should be attributed to an increased mean free path, wh ich induced a high density of atomic hydrogen and hydrocarbon radicals near the silicon surface. Atomic hydrogen can effectively etch the oxide layer on the surface of silicon and so greatly enhance the nucleation density. (C ) 2000 Published by Elsevier Science S.A. All rights reserved.