  The chemical bonding in an epitaxial ZrB2 film is investigated by Zr K-edge
(1s) X-ray absorption near-edge structure (XANES) and extended X-ray absorption
fine structure (EXAFS) spectroscopies and compared to the ZrB2 compound target
from which the film was synthesized as well as a bulk {\alpha}-Zr reference.
Quantitative analysis of X-ray Photoelectron Spectroscopy spectra reveals at
the surface: ~5% O in the epitaxial ZrB2 film, ~19% O in the ZrB2 compound
target and ~22% O in the bulk {\alpha}-Zr reference after completed sputter
cleaning. For the ZrB2 compound target, X-ray diffraction (XRD) shows weak but
visible -111, 111, and 220 peaks from monoclinic ZrO2 together with peaks from
ZrB2 and where the intensity distribution for the ZrB2 peaks show a randomly
oriented target material. For the bulk {\alpha}-Zr reference no peaks from any
crystalline oxide were visible in the diffractogram recorded from the
0001-oriented metal. The Zr K-edge absorption from the two ZrB2 samples
demonstrate more pronounced oscillations for the epitaxial ZrB2 film than in
the bulk ZrB2 attributed to the high atomic ordering within the columns of the
film. The XANES exhibits no pre-peak due to lack of p-d hybridization in ZrB2,
but with a chemical shift towards higher energy of 4 eV in the film and 6 eV
for the bulk compared to {\alpha}-Zr (17.993 keV) from the charge-transfer from
Zr to B. The 2 eV larger shift in bulk ZrB2 material suggests higher oxygen
content than in the epitaxial film, which is supported by XPS. In EXAFS, the
modelled cell-edge in ZrB2 is slightly smaller in the thin film (a=3.165 {\AA},
c=3.520 {\AA}) in comparison to the bulk target material (a=3.175 {\AA},
c=3.540 {\AA}) while in hexagonal closest-packed metal ({\alpha}-phase, a=3.254
{\AA}, c=5.147 {\AA}).
