Study of the Phase Transformation of Single Particles of Ga2O3 by UV‐Raman Spectroscopy and High‐Resolution TEM

Abstract 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 2 O 3 and then into β‐Ga 2 O 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 2 O 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 2 O 3 into β‐Ga 2 O 3 , the nucleation of β‐Ga 2 O 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 2 O 3 . By finely controlling the process of the phase transformation, the β‐Ga 2 O 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 2 O 3 single particles can be easily tuned and a particle with an α@β core–shell phase structure has been obtained.