  Boron carbide thin films of different thicknesses deposited by ion beam
sputtering were studied. The deposited films were characterized by grazing
incidence hard x-ray reflectivity (GIXR), resonant soft x-ray reflectivity
(RSXR), x-ray photo electron spectroscopy (XPS), resonant Rutherford
backscattering spectrometry (RRBS), and time of flight secondary ion mass
spectrometry (TOF-SIMS). An in-depth profile of the chemical elements
constitute the films is reconstructed based on analysis of reflectivity curves
measured in the vicinity of B K-edge. The composition of films is closely
dependent on film thickness. Boron to Carbon (B/C) ratio reaches to ~4 as the
thickness of deposited films increases. The B/C ratio estimated from RSXR
measurements are in agreement with the RRBS measurements. TOF-SIMS data also
suggested that decrease in boron content with decrease in film thickness. XPS
measurements confirm the presence of little amount of B atoms on the surface of
low thickness film.
