Ga2O3 nanoparticles synthesized in a low-pressure flame reactor
Ga2O3 was synthesized by doping a H2/O2/Ar premixed flat flame with diluted trimethyl gallium Ga(CH3)3 in a low pressure reactor. The mean particle diameter dp of the resulting metal oxide was characterized in-situ with a particle mass spectrometer (PMS), and was observed to range between 2.5 nm ? dp ? 6.5 nm. This result was further collaborated by BET measurements. XRD results show that the as-synthesized Ga2O3 nanoparticles are mostly amorphous, although, a few broad reflexes indicating the presence of some degree of crystallinity were observed. Thermal annealing of the as-synthesized material at 1000°C for 5 minutes yielded ?-Ga2O3 with a monoclinic structure. Transmission electron microscope TEM image analysis showed that the particles are agglomerated, but have spherical morphology. UV-VIS measurement indicates strong absorption in the UV range (4.8 eV), which corresponds quite well to the direct band gap of bulk Ga2O3. Photoluminescence (PL) measurement of the as-synthesized metal oxide indicates a broad emission spectrum (blue light) ranging from 350 to 600 nm with a maximum at 460 nm. Crystalline ?-Ga2O3 exhibited higher luminescence than as-synthesized particles, with a significant red shift at higher temperatures.
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