【International Papers】Optical activity and phase transformations in γ/β Ga₂O₃ bilayers under annealing

      Researchers from the University of Oslo have published a dissertation titled "Optical activity and phase transformations in γ/β Ga₂O₃ bilayers under annealing " in arXiv.

Abstract

      Gallium oxide (Ga₂O₃) can be crystallized in several polymorphs exhibiting different physical properties. In this work, polymorphic structures consisting of the cubic defective spinel (gamma) film on the top of the monoclinic (beta) substrate were fabricated by disorder-induced ordering, known to be a practical way to stack these polymorphs together. Such bilayer structures were annealed to investigate the optical properties and phase transformations. Specifically, photoluminescence and diffuse reflectance spectroscopies were combined with transmission electron microscopy, Rutherford backscattering/channeling spectrometry and x-ray diffraction to monitor the evolutions. As a result we observe a two-stage annealing kinetics in gamma/beta Ga₂O₃ bilayers associated with the epitaxial gamma-to-beta regrowth at the interface at temperatures below 700 °C and a non-planar gamma-to-beta phase transformation starting at higher temperatures. Thus, the present data enhance understanding of the polymorphism in Ga₂O₃, interconnecting the phase transformation kinetics with the evolution of the optical properties.

Figure 1. Systematic structural analysis of γ/β bilayer anneals. (a) RBS/C spectra and (b) corresponding XRD 2Q scans of γ/β Ga₂O₃ bilayers before and after annealing as indicated in the legends. The peak marked by star in the panel (b) is because of the sample holder. The RBS/C and XRD spectra of the unimplanted (virgin) β-Ga₂O₃ samples are also included in the corresponding panels for comparison. Dashed-dotted line illustrates the nuclear energy loss vs depth profile calculated with SRIM code, with arrow point the R_pd.

Original link:https://doi.org/10.48550/arXiv.2405.20011