(color online) XPS analysis of the recovered diamond–cBN–B₄C–Si sample. (a)–(d) XPS spectra for B 1s, C 1s, N 1s, and Si 2p core levels for the sample synthesized at 5.2 GPa/1680 K for 3 min. A combination of Gaussian and Lorentzian were used in the fitting of observed spectra. Different binding energies for each element suggest multiple bonding in the sample.