Characterization of amorphous carbon thin films

Abstract

The objective of this study is to develop improved procedures for characterizing amorphous carbon films. Raman spectroscopy is used to characterize amorphous carbon thin films grown by pulsed laser deposition at temperatures between 293 and 873 K. The amount of bond-angle disorder is shown to decrease with increasing substrate temperature. However, a shift of the Raman D peak to higher wave numbers is not observed to coincide with the presumed decrease in sp3 bonding as the deposition temperature increases. The graphitic domain size is shown to initially decrease, pass through a minimum, and then increase as temperature increases. Mass densities, measured independently by x-ray specular reflectometry, are seen to decrease from a maximum of 2.4 g/cm−3 as deposition temperature increases. The trend in the observed density measurements correlates well with the Raman spectroscopy data. The importance of x-ray specular reflectometry as part of a strategy to completely characterize amorphous carbon films is discussed in terms of these data.