Effects of secondary pretreatments of substrate on the nucleation of diamond film
- PDF / 768,788 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 24 Downloads / 231 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Effects of secondary pretreatments of substrate on the nucleation of diamond film W. S. Yang and Jung Ho Je Department of Materials Science and Engineering, Pohang University of Science & Technology, San 31, Hoyja Dong, Pohang, Kyungbuk 790-784, Republic of Korea (Received 14 December 1995; accepted 22 February 1996)
The effects of secondary pretreatments on diamond nucleation were investigated for the Si substrates pretreated by the diamond abrasion. When the substrate was just abraded with diamond powder, the nucleation density of diamond was 7 3 108ycm2 . However, the nucleation density was found to be greatly decreased by various secondary pretreatments except by one wet chemical etching method. The nucleation density was reduced to 3 3 107ycm2 by the chemical etching (I), to 7 3 106ycm2 by the H2 plasma etching, and to ,104ycm2 by the Ar sputtering, or O2 plasma etching. It was very slightly reduced to 3 3 108ycm2 by the chemical etching (II). The effects of secondary pretreatments in reducing the nucleation density were found to be very closely related to the removal of diamond seeds rather than topographic sites or structural defects. Therefore, diamond seeds generated by the diamond abrasion are considered as the main nucleation sites of diamond.
I. INTRODUCTION
Diamond films, grown by chemical vapor deposition (CVD), have potentially attractive applications due to the diamond’s excellent and unique properties. One critical issue in realizing most of these applications is a sound understanding of the nucleation mechanism on foreign substrates.1 The nucleation density of diamond on foreign substrates, except c-BN, is generally very low for growing a continuous film from an early stage of growth. Various substrate pretreatments have been proposed for enhancing the nucleation density, and a common and reliable one is the abrasion of substrate surface with diamond powder.2 Diamond abrasion is known to enhance the nucleation density up to 106–10ycm2 .3,4 Some possible mechanisms have been suggested to explain the role of diamond abrasion in enhancing diamond nucleation.2 They mainly include the plantation of diamond seeds,4–6 the generation of structural defects,7–9 and the creation of concave10,11 or prominent12,13 topographic sites on the substrate surface. However, it is considered that diamond abrasion can produce three possible nucleation sites simultaneously.12,14 This makes it more difficult to find out which of them acts as the main nucleation sites of diamond. If the three possible nucleation sites mentioned above can be controlled independently, it may be possible to find out the main nucleation sites. Some additional pretreatments have also been proposed to reduce the nucleation density on the Si substrate pretreated by diamond abrasion for the selective growth of diamond film.15 They include the Ar1 ion beam etching,7,16 KrF eximer laser irradiation,17 and the plasma etching by using H2 gas18,19 or the mixture gas of J. Mater. Res., Vol. 11, No. 7, Jul
Data Loading...
