Ellipsometric study of thin carbon films deposited by pulsed laser deposition

Abstract

The fabrication of nano-crystalline carbon films was implemented by the application of pulsed laser deposition (PLD) technology. The experiments were performed in a standard on-axis laser ablation (LA) configuration. The third harmonic of a Nd:YAG laser was used for ablation of a microcrystalline graphite target. All experiments were performed in vacuum at a pressure of 1×10-3 Pa for different deposition times. (001) Oriented silicon (Si) covered by either 350 or 450 nm silica (SiO2) layer was used as a substrate. The films have a thickness between 4 and 40 nm and are characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM) and ellipsometry measurements. We established deposition of nano-sized graphene-like films on top of predominantly amorphous carbon films with a thickness of 1- 2 nm. The measured the (n and k) and determined the values for the forbidden gap of the films which are between 0.01 eV and about 1 eV with reference to the sp3 hybridized carbon content of the film.