Layers of BN were deposited onto substrates by means of spark discharge. The layer diffusion sources gave reproducible B distributions, with homogeneous surface concentrations. The amount of B which diffused was determined only by heat treatment at 850 to 950C. The B profiles corresponded to a Gaussian distribution and, using the 4-point diffusivity method, it was found that the diffusivity could be described by:

D (cm2/s) = 1.15 x 101 exp[-3.77(eV)/kT]

H.J.Schnabel, F.Fleischer: Physica Status Solidi A, 1971, 8[1], 71-8