2024/05/01 by Jian Tang, Tang, J., Kai Jiang +9
Materials Science · Energy · #Ga2O3 and related materials #Advanced Photocatalysis Techniques #Electronic and Structural Properties of Oxides
paper · pdf · doi:10.48550/arxiv.2405.00299
Phase transitions in metastable α-, κ(ε)-, and γ-Ga2O3 films to thermodynamically stable β-Ga2O3 during annealing in air, N2, and vacuum have been systematically investigated via in-situ high-temperature X-ray diffraction and scanning electron microscopy. These respective polymorphs exhibited thermal stability to around 471-525^∘C, 773-825^∘C, and 490-575^∘C before transforming into β-Ga2O3, across all tested ambient conditions. Particular crystallographic orientation relationships were observed before and after the phase transitions, i.e., (0006) α-Ga2O3 ∥ (402) β-Ga2O3, (004) κ(ε)-Ga2O3 ∥ (310) and (402) β-Ga2O3, and (400) γ-Ga2O3 ∥ (400) β-Ga2O3. The phase transition of α-Ga2O3 to β-Ga2O3 resulted in catastrophic damage to the film and upheaval of the surface. The respective primary and possibly secondary causes of this damage are the +8.6% volume expansion and the dual displacive and reconstructive transformations that occur during this transition. The κ(ε)- and γ-Ga2O3 films converted to β-Ga2O3 via singular reconstructive transformations with small changes in volume and unchanged surface microstructures.