Morphology of Optically Transparent Cubic Silicon Carbide Prepared by Chemical Vapor Deposition
- PDF / 1,404,708 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 54 Downloads / 188 Views
Michael W. Russell§,*, Jaime A. Freitas, Jr.¥ and James E. Butler* § NRC Postdoctoral Research Associate * Naval Research Laboratory, Washington, DC 20375 ¥ Sachs/Freeman Associates, Landover, MD 20785 Abstract
Crystals of cubic silicon carbide (3C-SiC) were grown in an RF-induction furnace on graphite substrates by atmospheric pressure chemical vapor deposition (APCVD) from a single precursor, methyltrichlorosilane (MTS) in hydrogen. 'The deposits were characterized by micro-Raman spectroscopy, x-ray diffraction, and atomic force and scanning electron microscopies. Above -1600°C preferential growth directions were identified for the majority of the crystals. At intermediate deposition temperatures (1600-1700'C) the dominant morphology consisted of yellow prismatic crystals heavily twinned along {111) and {111 . At substrate temperatures exceeding -1750°C hexagonally-shaped (1111 oriented 3C-SiC platelets were formed with alternating {001 }/( 101) edges. The dependence of nucleation density, film morphology and film orientation on deposition conditions will be discussed with emphasis on the growth of high quality single crystals of 3C-SiC. Introduction
In addition to its superior mechanical properties, the wide band gap (2.3 eV), high 2 1 breakdown field (-5x10 6 Vcm-1), and high saturated electron velocity (-1000 Vcm- s- ) of cubic silicon carbide (3C-SiC) make it an attractive candidate for elevated-temperature, highfrequency, and high-power electronic devices [1]. Chemical vapor deposition has been demonstrated to yield dense, high purity 3C-SiC which has found applications as wear and corrosion-resistant coatings and as a semiconductor device material particularly in aggressive environments [2]. Previous work at the A.A. Baikov Institute in Moscow demonstrated that high-quality, high-purity 3C-SiC single crystals (-3 mm) could be grown on resistively heated graphite rods by APCVD using MTS in H2 [3]. Earlier results from NRL have also demonstrated that high quality 3C-SiC was deposited at -16500C under conditions of low MTS concentration in H2 [4]. An important objective of this study was to examine the effect of deposition parameters on the microstructure of the deposited layers. Deposition conditions which favored platelet growth were of particular interest. Experimental Procedure
The growth of 3C-SiC was carried out at atmospheric pressure by the thermal decomposition of methyltrichlorosilane (MTS) in excess hydrogen in a vertical, cold-walled quartz reaction chamber (2.54 cm ID x 30.5 cm). A 5 kW RF induction power supply was used to heat a cylindrical graphite substrate (1.83 cm ' x 2.54 cm) which was supported in the quartz tube by a molybdenum rod. Prior to each deposition run the reaction chamber was evacuated to 0.1 torr and then purged with hydrogen. The substrate was preheated for 30 minutes in flowing hydrogen at the deposition temperature prior to initiating the MTS flow. The hydrogen flow rate was controlled with a mass flow controller. The MTS precursor was maintained in a constant temperature
Data Loading...
