The Effect of Stress in the Density of States of Amorphous Carbon Films Determined by X-Ray Excited Auger Electron Spectroscopy

P F Barbieri,F C Marques

doi:10.1155/2017/5826527

Abstract

Amorphous carbon films can be prepared with a large variety of structure and have been used in a number of technological applications. Many of their properties have been determined, but very little is known concerning the effect of pressure on their properties. In this work we investigate the influence of pressure of graphite-like amorphous carbon films on the density of states (DOS) using X-ray Excited Auger Electron Spectroscopy (XAES) and the second derivate method of the XAES. The films were deposited by ion beam deposition and simultaneously bombarded with argon, which is responsible for the variation of the film stress, reaching extremely high values (4.5 GPa). Marked variations of the density of states of the pπ, pσ, sp, and s components were observed with increasing stress.

Highlights

Amorphous carbon films (a-C) have been investigated and technologically applied for decades due to their interesting properties such as high hardness, low friction coefficient, and chemical inertness or even as a matrix host for the implantation of other elements [1,2,3]
In this paper we studied a-C thin films using the second derivative method to determine, for the first time, the influence of the internal pressure of the carbon matrix and how it affects the band states
After X-ray Excited Auger Electron Spectroscopy (XAES) measurements, the stress of the a-C films was measured using the “bending beam technique” using the radius of curvature of film/substrate composite obtained by the deflection of a He-Ne laser beam

Summary

Introduction

Amorphous carbon films (a-C) have been investigated and technologically applied for decades due to their interesting properties such as high hardness, low friction coefficient, and chemical inertness or even as a matrix host for the implantation of other elements [1,2,3]. In this paper we studied a-C thin films using the second derivative method to determine, for the first time, the influence of the internal pressure (using the intrinsic stress) of the carbon matrix and how it affects the band states. The samples exhibit high intrinsic stress, when compared to other techniques, and it is expected that the stress influences the most external electronic states, composed of s-p hybridized orbitals. Such influences can be perceived by spectroscopic techniques through changes in the line shape spectrum, the intensities and energy peaks, and peak-to-peak energies. The spectroscopy techniques normally investigate occupied states (σ and π orbitals) of DOS in the valence band

Experimental

Results and Discussions

Conclusion