Spectral Absorption Properties of Ultrananocrystalline Diamond/Amorphous Carbon Composite Thin Films Prepared by Pulsed Laser Deposition

Abstract

The spectral absorption properties of ultrananocrystalline diamond (UNCD)/amorphous carbon composite films grown by pulsed laser deposition with graphite were experimentally investigated. The indirect optical band gaps estimated from the absorption spectrum were 1.0 eV and approximately 5.65 eV, which correspond to those for the amorphous carbon surrounding the UNCDs and for UNCDs themselves, respectively. In addition, the spectrum revealed a direct gap having a value of approximately 2.2 eV. One probable origin can be the presence of grain boundaries between UNCDs and amorphous carbon since they are specific to UNCD/amorphous carbon; further, its appearance is consistent with the theoretical predictions.