Experimental study of surface electronic properties of ECR-PECVD deposited a-C1−xNx:H films using UPS, XPS and spectroscopic ellipsometry

Electronic properties of a-C1−xNx:H (0<x<0.1) films deposited using ECR-plasma decomposition of C2H2/N2 precursor gases have been investigated by combining photoelectron spectroscopy (PES) and UV–Vis spectroscopic ellipsometry (SE). Estimates of band positions with respect to the Fermi-level have been obtained. Ultraviolet photoemission spectroscopy (UPS) supplies the work function and the valence band maximum of the a-C1−xNx:H surface, for as entered, heated and sputter cleaned samples. The extraction of the conduction band minimum from the combination of Tauc/E04 gap from SE analysis and the UPS valence band maximum is investigated. Furthermore, the most promising results from the current investigation, is the positioning of π states from data analysis of the UPS spectra, and π∗ states from the combination of UPS and SE. The results show that a-C:H is p-type, lightly N doped a-C1−xNx:H is n-type, while in the higher N doped a-C1−xNx:H the Fermi-level seems to be pinned near the midgap.