Development of Amorphous Carbon-Based Variable Optical Gap Semiconductor Materials

Abstract

Amorphous carbon (a-C) based semiconductor materials with variable optical gap and high semiconductor properties could be successfully fabricated by radio frequency plasma enhanced chemical vapor deposition (RF-PeCVD) method using a mixed solution of tetramethylsilane (TES) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS) as a liquid source. The optical gap could be controlled by varying sizes and number of sp 2 clusters included in multi-phase structure of a-C by incorporating Si atoms. The resulting Si-doped a-C with 10 six-membered rings in sp 2 clusters shows 1.76 eV of optical gap and Si-doped a-C with 4 six-membered rings in sp 2 clusters shows 2.76 eV. From photocurrent measurement under UV exposure, it was clarified that these films functioned as high performance n-type semiconductors with ca. 4 % of quantum yield, which was on the same level as that obtained at anatase-type titanium oxide prepared by the sol-gel method.