NUCLEATION OF BORON-NITRIDE THIN-FILMS ON NI(100)

The initial stages of BN growth on Ni(100) have been studied by means of thermal desorption mass spectrometry (TDS), X-ray photoelectron spe ctrometry (XPS), and low-energy electron diffraction (LEED). TDS and X PS measurements have shown that condensed multilayers of B2H6 and NH3 coadsorbed on Ni(100) at low temperature will react during heating to form sub-monolayer coverages of BN. This reaction was observed to occu r in the absence of electron irradiation, indicating that the reaction between B2H6 and NH3 to form BN on the Ni(100) surface can be thermal ly activated. Under low-pressure (<10(-6) Torr) growth conditions, exp osing Ni(100) to both B2H6 and NH3 simultaneously at 950 K results in self-limiting BN growth. XPS measurements of the BN films grown at low pressure indicate the formation of roughly one monolayer of BN on the Ni(100) surface. LEED of the BN film grown at 950 K was found to prod uce a (1 x 7) diffraction pattern. This diffraction pattern is consist ent with the formation of a monolayer of strained hexagonal BN on the Ni(100) surface. The BN monolayer on the Ni(100) surface was found to be quite stable in atmosphere, with no detectable oxidation after expo sure to atmosphere for several days. Subsequent growth of BN by MOCVD (at 76 Torr) on the BN-covered Ni(100) surface leads to further growth of hexagonal BN overlayers. (C) 1997 Elsevier Science B.V.