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.
Figure 1b)
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.
Figure 2: Angular
dependence of the B 1s absorption spectra for the iBN film.
The inset shows that q is the polar angle between the
incident x-ray wavevector and the normal to the surface of
the film. The spectra have been vertically separated for ease
of comparison. The p* features are largest near normal
incidence and decrease in normalized intensity as the angle
between the incident x-ray beam and the surface normal
increases.
Figure 3: Angular
variation of the integrated intensity of the largest peak in
the p* portion of the iBN B 1s spectra. The form I (q) =
cos2q is expected if the hexagonal layer planes lie
orthogonal to the Si surface with the p bonds in the plane of
the film.