Extended Data Fig. 6: Nanoindentation and nanoscratch test results.

a, b, Nanoindentation results showing that the deposition of a-BN on Si substrates leads to an enhancement in surface hardness and stiffness. The average and standard deviation values for the hardness in b are 11.31 ± 0.13 for a-BN on Si and 10.93 ± 0.09 for bare Si. c, Nanoscratch test results revealing that a scratch depth of 40 nm (more than 10 times the film thickness) is required to delaminate the film, which suggests excellent adhesion with the Si substrate. Scanning electron microscopy observations show that the scratch regions are clean, with no evidence of delamination of a-BN for a scratch depth smaller than 40 nm. The datasets 1–4 in the bottom panel represent scratch test data obtained at four different positions under the same experimental conditions.