β-Ga2O3 nanostructures, including nanowires (NWs), nanosheets (NSHs), and nanorods (NRs), were synthesized using thermally dewetted Au nanoparticles as catalyst in a chemical vapor deposition process. The morphology of the as-grown β-Ga2O3 nanostructures depends strongly on the growth temperature and time. Successful growth of β-Ga2O3 NWs with lengths of 7-25 μm, NSHs, and NRs was achieved. It has been demonstrated that the vapor-liquid-solid mechanism governs the NW growth, and the vapor-solid mechanism occurs in the growth of NSHs and NRs. The X-ray diffraction analysis showed that the as-grown nanostructures were highly pure single-phase β-Ga2O3. The bandgap of the β-Ga2O3 nanostructures was determined to lie in the range of 4.68-4.74 eV. Characteristic Raman peaks were observed with a small blue and red shift, both of 1-3 cm-1, as compared with those from the bulk, indicating the presence of internal strain and defects in the as-grown β-Ga2O3 nanostructures. Strong photoluminescence emission in the UV-blue spectral region was obtained in the β-Ga2O3 nanostructures, regardless of their morphology. The UV (374-377 nm) emission is due to the intrinsic radiative recombination of self-trapped excitons present at the band edge. The strong blue (404-490 nm) emissions, consisting of five bands, are attributed to the presence of the complex defect states in the donor (VO) and acceptor (VGa or VGa-O). These β-Ga2O3 nanostructures are expected to have potential applications in optoelectronic devices such as tunable UV-Vis photodetectors.
Keywords: chemical vapor deposition; gallium oxide β-Ga2O3; nanostructures; nanowires; photoluminescence; semiconductor.