Chemical synthesis and band gap control of Ga2O3:Co nanocrystals

Chemical synthesis of Ga2O3:Co was carried out for band gap control. As the amount of Co added increased, uniform fibrous Ga2O3 nanocrystals became irregular and the film-like structures appeared. By X-ray diffraction evaluation, nanocrystals were confirmed to be e-type when the addition of Co was increased up to (GaCl3:CoCl2) = 2:1 molar ratio of raw materials. It was suggested that the crystal changed to γ-Ga2O3 at molar ratios over 1:1. Evaluation of the energy band structure based on the optical absorption spectra, it was found that the band gap widened as the addition of Co was small. The band gap conversely narrowed when the addition was increased from the molar ratio of 2:1 to 1:2. As a result, the band gap was controlled in the range of 4.6 to 5.6 eV.