Influence of deposition temperature on the structure, optical and electrical properties of a-C films by DCMS

Amorphous carbon films have been considered as strongly promising semiconductor materials, due to their superior mechanical properties, specific bond structures, as well as facile deposition over large area with device integrated processes. To figure out the effect of sp(2)/sp(3) ratio and size of sp(2) clusters on opto-electrical behavior, we fabricated a series of H-free amorphous carbon (a-C) films by magnetron sputtering with a controllable deposition temperature from 30 to 400 degrees C. Result showed that all the films displayed a strong light absorption in the ultraviolet and visible regions, where the transmittance was less than 5% in the wavelength range of 200-750 nm, demonstrating the typical semiconductor behavior in temperature from 5 to 350 K, exhibiting a lower resistivity at higher temperature. In addition, their transmittance, optical bandgap, resistivity and activation energy showed similar tendency with increasing deposition temperature, which was discussed in terms of the evolution of sp(2)/sp(3) ratio and sp(2) cluster in the a-C films. These studies provide a new route to tune optical and electrical properties of a-C films for their opto-electrical applications.