Fabrication of Graded Band Gap Amorphous Carbon Nitride Thin Films for New Generation Photovoltaic Applications

Abstract

We have reported the fabrication of amorphous carbon nitride, a-CNx, films with a graded band gap structure to improve their photoconductivity and their structural, optical, and electrical properties are studied. In this study, two different structured a-CNx films with graded band gap structures were compared with single-layered a-CNx films. One of the graded band gap structure films consists of four stacked layers with different band gaps (multilayered film), and the other film consists of one layer with a gradually changed band gap (graded-layered film). All of the a-CNx films are prepared by the reactive radio frequency magnetron sputtering method using a graphite target in pure nitrogen gas. The ratio of photo- and dark-conductivity, σp/σd, of the multilayered film is quite low. In contrast, the σp/σd value of the graded-layered a-CNx film is about 11 times larger than that of the single-layered film and 80 times larger than that of the multilayered film.