Tunable Optical Properties of Amorphous-Like Ga2O3 Thin Films Deposited by Electron-Beam Evaporation with Varying Oxygen Partial Pressures.

Shijie Li,Chen Yang,Linpeng Dong,Changlong Cai,Jin Zhang,Weiguo Liu,Haifeng Liang

doi:10.3390/nano10091760

Shijie Li, Chen Yang + Show 5 more

Open Access

https://doi.org/10.3390/nano10091760

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Abstract

Ga2O3 thin films were fabricated by the electron-beam evaporation technique at a varying oxygen partial pressure from 0 to 2.0 × 10−2 Pa. The effect of oxygen partial pressure on the crystalline structure and optical properties of the Ga2O3 films was analyzed using sophisticated techniques including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, spectroscopic ellipsometry, ultraviolet-visible spectroscopy and a laser-induced damage test system. The correlation between the oxygen partial pressure and the film’s properties in optics and materials were investigated. XRD and Raman revealed that all films were amorphous in spite of applying a varying oxygen partial pressure. With the change of oxygen partial pressure, XPS data indicated that the content of oxygen in the Ga2O3 films could be broadly modulable. As a result, a changeable refractive index of the Ga2O3 film is realizable and a variable blue-shift of absorption edges in transmittance spectra of the films is achievable. Moreover, the damage threshold value varied from 0.41 to 7.51 J/cm2 according to the rise of oxygen partial pressure. These results demonstrated that the optical properties of Ga2O3 film can be broadly tunable by controlling the oxygen content in the film.

Highlights

Gallium oxide (Ga2O3) possesses diverse crystalline phases such as α, β, γ, δ, ε-Ga2O3 and so on [1]
The preparation of Ga2O3 thin films have been finalized by low-pressure chemical vapor deposition (LPCVD) [7], mist chemical vapor deposition [8], metal-organic chemical vapor deposition (MOCVD) [9], halide vapor phase epitaxy (HVPE) [10], pulsed laser deposition (PLD) [11], hydrothermal [12], sol-gel [13] and sputtering [14]
Considering the optical properties of Ga2O3 thin films are greatly affected by oxygen partial pressure, the properties of the thin film, such as stoichiometry, microstructure, and optical characteristics, have been comprehensively analyzed under the different oxygen partial pressures

Summary

Introduction

Gallium oxide (Ga2O3) possesses diverse crystalline phases such as α-, β-, γ-, δ-, ε-Ga2O3 and so on [1]. Our investigation intentionally planned to focus on the optical properties of the amorphous-like Ga2O3 thin films commonly applied in optics field, which were deposited by a low-cost and larger-scale deposition method of electron-beam evaporation. Considering the optical properties of Ga2O3 thin films are greatly affected by oxygen partial pressure, the properties of the thin film, such as stoichiometry, microstructure, and optical characteristics, have been comprehensively analyzed under the different oxygen partial pressures. This investigation would be beneficial for exploring our new knowledge of fundamental properties of Ga2O3 films

Experimental Details

Results and Discussions

Optical Properties of Ga2O3 Films