High-Pressure Synthesis and Characterization of β‑GeSeA Six-Membered-Ring Semiconductor in an Uncommon Boat Conformation

• Published in: Journal of the American Chemical Society Vol. 139; no. 7; pp. 2771 - 2777
• Main Authors: von Rohr, Fabian O, Ji, Huiwen, Cevallos, F. Alexandre, Gao, Tong, Ong, N. Phuan, Cava, Robert J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 22-02-2017
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.6b12828

Two-dimensional materials have significant potential for the development of new devices. Here we report the electronic and structural properties of β-GeSe, a previously unreported polymorph of GeSe, with a unique crystal structure that displays strong two-dimensional structural features. β-GeSe is made at high pressure and temperature and is stable under ambient conditions. We compare it to its structural and electronic relatives α-GeSe and black phosphorus. The β form of GeSe displays a boat conformation for its Ge–Se six-membered ring (“six-ring”), while the previously known α form and black phosphorus display the more common chair conformation for their six-rings. Electronic structure calculations indicate that β-GeSe is a semiconductor, with an approximate bulk band gap of Δ ≈ 0.5 eV, and, in its monolayer form, Δ ≈ 0.9 eV. These values fall between those of α-GeSe and black phosphorus, making β-GeSe a promising candidate for future applications. The resistivity of our β-GeSe crystals measured in-plane is on the order of ρ ≈ 1 Ω·cm, while being essentially temperature independent.