Nucleation of boron nitride on Ni(100) surfaces

We report studies of the formation of boron nitride by decomposition of diborane (B2H6) and ammonia (NH3) on the Ni(100) surface. Diborane decomposes on the Ni(100) surface and is accompanied by the desorption of hydrogen, with the decomposition complete at 500 K. In the absence of ammonia, the boron on the surface reacts with the substrate to form a Ni2B phase. Boron nitride can be formed by heating ammonia and diborane multilayers from 100 K or by coadsorption of the two gases at temperatures above 800 K. The former procedure produces disordered, submonolayer coverages while the latter procedure produces ordered overlayers. A low energy electron difraction (LEED) pattern characteristic of an overlayer (1 x 7) is observed after growth at 950 K. This surface reconstruction appears to be consistent with the formation of a strained hexagonal boron nitride overlayer.