Structural analysis of carbon thin films deposited by pulsed laser deposition

The objective of the current study is to gain a greater understanding of the atomic structure of carbon films deposited by UV-pulsed-laser ablation. Films deposited onto Si substrates at 293 K, 473 K, 673 K, and 873 K are characterized using X-ray reflectometry and Raman spectroscopy. Film densities are shown to initially decrease from a maximum density of 2.39 g/cm³ as temperature increases. Above 673 K the density remains constant. When compared with Raman spectroscopy data, the reflectometry data are shown to be sensitive to microstructural changes within the films. The possibility of using density measurements as a boundary condition for more quantitative analysis is discussed. Also, Raman spectroscopy indicates that the graphitic domain size initially decreases, passes through a minimum, and then increases as temperature increases. The amount of bond-angle disorder is shown to decrease with increasing substrate temperature. However, an upward shift in frequency of the Raman D peak is not observed with the presumed decrease in sp³ bonding as the deposition temperature increases. These and other experimental results are presented and discussed.