Ga2O3 nanoparticles synthesized in a low-pressure flame reactor

Ga2O3 was-synthesized by doping a premixed H-2/O-2/Ar flat flame with diluted trimethyl gallium Ga(CH3)(3) in a low-pressure reactor. The mean particle diameter d(p) of the resulting metal oxide was characterized in-situ with a particle mass spectrometer (PMS), and was observed to range between 2.5 nm <= d (p) <= 6.5 nm. XRD results show that the as-synthesized Ga2O3 nanoparticles are mostly amorphous, although, a few broad reflexes were observed that indicate the presence of some degree of crystallinity. Thermal annealing of the as-synthesized material at 1000 degrees C for 5 min yielded beta-Ga2O3 with a monoclinic structure. UV-VIS measurements indicate strong absorption in the UV range (4.8 eV), which corresponds quite well to the direct band gap of bulk Ga2O3. Photoluminescence (PL) measurements of the as-synthesized metal oxide show a broad emission ranging from 350 nm to 600 nm with a maximum at 460 nm. Crystalline beta-Ga2O3 exhibited stronger luminescence than as-synthesized particles.