Figure 1

Figure 1a: Normal-incidence B 1s absorption spectra of the three types of BN. The spectra have been vertically offset and the cBN spectrum divided by 3 for clarity. Top, hBN powder; center, iBN/Si; bottom, cBN powder. The feature near 192.0 eV has p* final-state character, while the bands above about 194 eV have s* final-state character. As expected, the cBN shows only s-bonding.

(b) Normal-incidence N 1s absorption spectra of the three types of BN. The spectra have been offset as in (a). Once again, lower-energy p* features are prominent in the hBN and iBN.