Electronic structure of chromium-containing amorphous hydrogenated carbon thin films studied by X-ray absorption spectroscopy

C K-, Cr L _3.2 -, and K-edge X-ray absorption near-edge structure (XANES) analysis, high-resolution transmission electron microscopy examination, and optical absorptance have been examined to obtain a correlation between the optical absorptance and electronic structure of chromium-containing amorphous hydrogenated carbon thin films (a-C:H/Cr) deposited using a dc magnetron sputter deposition technique. It was found that the C 2pCr 3d hybridization gradually increases as the Cr nanoparticle (NP) size decreases, accompanied by a C 2p interband transition. The amount of CH bonding and the change in crystalline structure are the main factors affecting the optical absorptance of the thin films. The size of the Cr NP affects the absorption wavelength range of the films. The optical absorptance and C K-edge XANES spectra indicate that a decrease in the size of Cr NP raises the conduction-band-minimum and may also increase the bandgap.