Gulo Desman P, Yeh Han, Chang Wen-Hao, Liu Hsiang-Lin
Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan.
Department of Electrophysics, National Chiao Tung University, Hsinchu, 30010, Taiwan.
Sci Rep. 2020 Nov 4;10(1):19003. doi: 10.1038/s41598-020-76036-y.
PtSe has received substantial research attention because of its intriguing physical properties and potential practical applications. In this paper, we investigated the optical properties of bilayer and multilayer PtSe thin films through spectroscopic ellipsometry over a spectral range of 0.73-6.42 eV and at temperatures between 4.5 and 500 K. At room temperature, the spectra of refractive index exhibited several anomalous dispersion features below 1000 nm and approached a constant value in the near-infrared frequency range. The thermo-optic coefficients of bilayer and multilayer PtSe thin films were (4.31 ± 0.04) × 10/K and (-9.20 ± 0.03) × 10/K at a wavelength of 1200 nm. Analysis of the optical absorption spectrum at room temperature confirmed that bilayer PtSe thin films had an indirect band gap of approximately 0.75 ± 0.01 eV, whereas multilayer PtSe thin films exhibited semimetal behavior. The band gap of bilayer PtSe thin films increased to 0.83 ± 0.01 eV at 4.5 K because of the suppression of electron-phonon interactions. Furthermore, the frequency shifts of Raman-active E and A phonon modes of both thin films in the temperature range between 10 and 500 K accorded with the predictions of the anharmonic model. These results provide basic information for the technological development of PtSe-based optoelectronic and photonic devices at various temperatures.
由于其引人入胜的物理性质和潜在的实际应用，PtSe受到了大量的研究关注。在本文中，我们通过光谱椭偏仪在0.73 - 6.42 eV的光谱范围内以及4.5至500 K的温度下研究了双层和多层PtSe薄膜的光学性质。在室温下，折射率光谱在1000 nm以下表现出几个反常色散特征，并在近红外频率范围内接近一个恒定值。双层和多层PtSe薄膜在1200 nm波长处的热光系数分别为(4.31 ± 0.04)×10⁻⁴/K和(-9.20 ± 0.03)×10⁻⁴/K。室温下光学吸收光谱的分析证实，双层PtSe薄膜具有约0.75 ± 0.01 eV的间接带隙，而多层PtSe薄膜表现出半金属行为。由于电子-声子相互作用的抑制，双层PtSe薄膜的带隙在4.5 K时增加到0.83 ± 0.01 eV。此外，两种薄膜在10至500 K温度范围内拉曼活性E和A声子模式的频率偏移符合非谐模型的预测。这些结果为基于PtSe的光电器件和光子器件在不同温度下的技术发展提供了基本信息。
