Formation of Sic Films on Silicon Field Emitters
- PDF / 2,359,022 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 104 Downloads / 202 Views
FORMATION OF SiC FILMS ON SILICON FIELD EMI'ERS Jiang Liu, U. T. Son*, A. N. Stepanova**, K. N. Christensen, G. W. Wojak, E. I. Givargizov**, K. J. Bachmann, and John J. Hren Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC *Agency For Defense Development, R. 0. Korea "**Institute of Crystallography, Russian Academy of Sciences, Moscow, Russia
ABSTRACT Thin films of silicon carbide have been formed on silicon field emitters by chemical reaction with ethylene (C2 H 4 ) at temperatures of 850 to 9500C using ethylene gas pressures up to 5x10- 3 Torr. By controlling the reaction time and temperature, we have made SiC coatings of from -20 A thickness to complete transformation of tips to SiC (1-2 pm). The electron diffraction pattern of the SiC layers show the expected 20% lattice mismatch with silicon and, for those emitters completely transformed, a polycrystalline 3C-SiC polytype was identified. The small radius of curvature was maintained for both the coated and completely transformed tips, although some defects and surface roughness was introduced during the treatments.
. INTRODUCTION Silicon is a favored field emitter material for applications involving large arrays because of the highly developed technology for microfabrication. However, the propensity of clean silicon to react with its environment, especially with nanometer curved surfaces, makes silicon field emitters somewhat unstable. A previous study has shown that during the early stages of field emission, the surface of silicon emitters is modified by formation of a contamination layer which degrades the performance and can lead to failure [1]. Chemical modification of the silicon surface is one means to overcome these difficulties. Silicon carbide is a strong candidate material for coating silicon because of its excellent electronic, chemical, and mechanical properties [2-31. Films of 3C-SiC can usually be grown heteroepitaxially on SiC or a Si substrate by CVD or MBE [4-6]. Thin, smooth layers of SiC can also be formed by the chemical reaction of Si with gaseous hydrocarbons [7-9] which minimizes the stresses due to lattice mismatch and differences in thermal expansion coefficients between Si and SiC. Since field emitters must maintain their nanometer scale radius of curvature, such a growth mechanism is especially interesting. Unfortunately, all previous studies have been carried on flat Si substrates with orientation well defined. In contrast, a field emitter has nearly all crystal facets on its surface, a radius of curvature of a few nanometers and a shank diameter of only several microns. H. Experimental Procedures Sharp silicon single crystal whiskers were grown by the vapor-liquidMat. Res. Soc. Symp. Proc. Vol. 311. ©1993 Materials Research Society
22
solid (VLS) mechanism on the end of oriented 1xix1O mm silicon Such specimens are convenient to handle for transfers substrates [10]. During the present between the processing and characterizations steps. experiments, all whiskers except one favorably
Data Loading...
