Sozen Y, Yagmurcukardes M, Sahin H
Department of Photonics, Izmir Institute of Technology, 35430, Izmir, Turkey.
Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Phys Chem Chem Phys. 2021 Sep 29;23(37):21307-21315. doi: 10.1039/d1cp02299g.
In the present work, the identification of two hexagonal phases of germanium oxides (namely GeO and GeO) through the vibrational and optical properties is reported using density functional theory calculations. While structural optimizations show that single-layer GeO and GeO crystallize in 1T and buckled phases, phonon band dispersions reveal the dynamical stability of each structure. First-order off-resonant Raman spectral predictions demonstrate that each free-standing single-layer possesses characteristic peaks that are representative for the identification of the germanium oxide phase. On the other hand, electronic band dispersion analysis shows the insulating and large-gap semiconducting nature of single-layer GeO and GeO, respectively. Moreover, optical absorption, reflectance, and transmittance spectra obtained by means of GW-BSE calculations reveal the existence of tightly bound excitons in each phase, displaying strong optical absorption. Furthermore, the excitonic gaps are found to be at deep UV and visible portions of the spectrum, for GeO and GeO crystals, with energies of 6.24 and 3.10 eV, respectively. In addition, at the prominent excitonic resonances, single-layers display high reflectivity with a zero transmittance, which is another indication of the strong light-matter interaction inside the crystal medium.
在本工作中，利用密度泛函理论计算报告了通过振动和光学性质对两种氧化锗六方相（即GeO和GeO）的识别。结构优化表明，单层GeO和GeO分别结晶为1T相和屈曲相，声子能带色散揭示了每种结构的动力学稳定性。一阶非共振拉曼光谱预测表明，每个独立的单层都具有特征峰，这些峰是识别氧化锗相的代表性特征。另一方面，电子能带色散分析表明，单层GeO和GeO分别具有绝缘和大带隙半导体性质。此外，通过GW-BSE计算获得的光吸收、反射率和透射率光谱揭示了每个相中存在紧密束缚的激子，表现出强烈的光吸收。此外，对于GeO和GeO晶体，激子能隙分别位于光谱的深紫外和可见光部分，能量分别为6.24和3.10 eV。此外，在显著的激子共振处，单层显示出高反射率和零透射率，这是晶体介质内部强光-物质相互作用的另一个迹象。
