Abstract
In this study, an ab initio molecular dynamics method is employed to investigate the response behavior of α-Al2O3 to low energy irradiation. Different from the previous experiments, our calculations reveal that the displacements of oxygen dominate under electron irradiation and the created defects are mainly oxygen vacancy and interstitial. The experimental observation of the absorption peaks appearing at 203, 233 and 256 nm for α-Al2O3 under electron irradiations should be contributed by the oxygen defects and these defects will reduce the transmittance of α-Al2O3, which agrees well with the very recent experiment. This study demonstrates the necessity to reinvestigate the threshold displacement energies of α-Al2O3, and to introduce recombination center for oxygen defects to improve its optical properties and performance under radiation environment.
Highlights
The sapphire phase of alumina (α-Al2O3) is widely used for numerous industrial applications, such as catalyst support, solid state laser and photovoltaic devices[1, 2]
The lattice disorder induced by collective electronic excitation was confirmed by the Rutherford backscattering spectrometry in channeling geometry (RBS-C) analysis, and the optical absorption spectroscopy of α-Al2O3 exhibited the characteristic bands associated with oxygen vacancies[5]
Microstructural evolution in crystalline α-Al2O3 during Xe+ ion irradiation has been investigated by Okubo et al, who found that the swift heavy ion irradiation caused lattice expansion and the structural modification led to structural amorphization above the energy around 100 MeV10
Summary
The sapphire phase of alumina (α-Al2O3) is widely used for numerous industrial applications, such as catalyst support, solid state laser and photovoltaic devices[1, 2]. Its potential applications include components of breeder blanket and diagnostic windows, as well as coating in future fusion reactors to avoid the permeation of light gases[3] In these applications, α-Al2O3 is exposed to different kinds of radiation environment, i.e., neutron, low and swift heavy ions and γ-ray radiation. Α-Al2O3 is exposed to different kinds of radiation environment, i.e., neutron, low and swift heavy ions and γ-ray radiation This leads to the generation, migration and aggregation of defects or defect clusters, which may deteriorate the mechanical properties of materials and influence their performance. The presented results will be useful for understanding the structure-property relationship of α-Al2O3 and improving its properties and performances for its application as the substrate material for GaN growth for the production of blue light-emitting diode (LED), thin film passivation material for high-efficiency solar cells, luminescence dosimetry, and so on
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