Electrical and optical properties and structural changes of diamondlike carbon films during thermal annealing

Abstract

Diamondlike carbon films, prepared by the dual-ion-beam sputtering method on a glass substrate, were thermally annealed in vacuum for 30 min at 300 \ifmmode^\circ\else\textdegree\fi{}C, 400 \ifmmode^\circ\else\textdegree\fi{}C, 500 \ifmmode^\circ\else\textdegree\fi{}C and 600 \ifmmode^\circ\else\textdegree\fi{}C, respectively. Electrical resistivity, infrared transmittance, and Raman spectroscopy were used to characterize the films before and after annealing. The results showed that the vacuum thermal annealing caused a decrease and even the removal of bond-angle disorder, and an increase of the ${\mathit{sp}}^{2}$ C-C-bond-dominated crystallite size and/or number in the films. This then led to decreases in both film resistivity and optical transmittance of the specimens. Meanwhile, we found that the most substantial changes in structure and in electrical and optical properties occurred at a temperature higher than 400 \ifmmode^\circ\else\textdegree\fi{}C. It was concluded that the annealing effects of diamondlike carbon films in vacuum are nearly the same as those in hydrogen or in nitrogen atmospheres.