Study of the Phase Transformation of Single Particles of Ga_2O_3 by UV-Raman Spectroscopy and High-Resolution TEM

摘要

By taking advantage of UV-Raman spectroscopy and high-resolution TEM (HRTEM), combined with the focused ion beam (FIB) technique, the transformation from GaOOH into α-Ga_2O_3 and then into β-Ga_2O_3 was followed. We found that the stepwise transformations took place from the surface region before developing into the bulk of single particles without particle agglomeration and growth. During the transformation from GaOOH into α-Ga_2O_3, the elimination of water vapor through the dehydroxylation of GaOOH resulted in the formation of micropores in the single particles, whilst maintaining their particle size. For the phase transformation from α-Ga_2O_3 into β-Ga_2O_3, the nucleation of β-Ga_2O_3 was found to occur at the surface defects and this process could be retarded by occupying these defects with a small amount of La_2O_3. By finely controlling the process of the phase transformation, the β-Ga_2O_3 domains gradually developed from the surface into the bulk of the single particles without particle agglomeration. Therefore, the surface structure of the α-Ga_2O_3 single particles can be easily tuned and a particle with an α@β core-shell phase structure has been obtained.