AUTHOR=Zhao Yi-Feng , Guan Zhao , Zhong Ni , Yue Fang-Yu , Xiang Ping-Hua , Duan Chun-Gang 

TITLE=Raman Spectra of Bulk and Few-Layer GeSe From First-Principles Calculations

JOURNAL=Frontiers in Materials

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2021.736057

DOI=10.3389/fmats.2021.736057

ISSN=2296-8016

ABSTRACT=<p>Raman spectra play a significant role in the study of polar materials. Herein, we report the influence of strain and interlayer shift on vibration responses in bulk and few-layer ferrovalley material GeSe in different polarization states (ferroelectric/FE and antiferroelectric/AFE) based on density functional theory and density functional perturbation theory calculations. We find <italic>A</italic><sub><italic>g</italic></sub><sup>1</sup> mode shifts by about 10 cm<sup>−1</sup> from monolayer to bilayer and trilayer due to the interlayer coupling. The <italic>A</italic><sub><italic>g</italic></sub><sup>3</sup> mode on behalf of FE mode is observed that is consistent with the experiments in bulk and few-layer GeSe. Meanwhile, in our calculations, with the transition between AFE and FE state in the bilayer and trilayer, the Raman frequency of <italic>A</italic><sub><italic>g</italic></sub><sup>2</sup> and <italic>A</italic><sub><italic>g</italic></sub><sup>3</sup> mode decrease obviously whereas that of <italic>A</italic><sub><italic>g</italic></sub><sup>1</sup> mode increases. Interestingly, the Raman peaks shifted a lot due to the strain effect. We expect these variations in the Raman spectroscopy can be employed to identify the status of GeSe films, e.g., the AFE or FE state, and the number of layers in experiments.</p>