Monochalcogenides of germanium (or tin) are considered as isoelectronic and isostructural analogues of black phosphorus. Here, we demonstrate the synthesis of atomically thin GeSe by direct sonication-assisted liquid phase exfoliation (LPE) of bulk microcrystalline powders in organic solvents. The thickness of the GeSe sheets is dependent on the exfoliation conditions, and highly crystalline few-layer GeSe sheets of 4–10 layer stacks with lateral sizes over 200 nm were obtained. In ambient atmosphere, the LPE sheets deposited on the substrate demonstrate strong resistance against degradation, while decomposition into elemental Ge and Se nanostructures occurs at a moderate rate for ethanol dispersions. Density functional theory calculation together with optical characterizations confirm the blue-shifted bandgap for the GeSe sheets as a result of strong quantum confinement effect. In addition, we show that the few-layer GeSe sheets with favorable optical bandgap allow for efficient solar light harvesting for photocurrent generation based on a photoelectrochemical cell. Our joint theoretical and experimental results suggest that GeSe sheets of atomic thickness could be a new two-dimensional semiconductor that can be exploited for potential applications in optoelectronics and photonics.

中文翻译：

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二维GeSe作为磷的同构和等电子类似物：超声辅助合成，化学稳定性和光学性质

锗（或锡）的单硫族化物被认为是黑磷的等电子和同构类似物。在这里，我们演示了通过在有机溶剂中直接超声辅助大块微晶粉末的液相剥落（LPE）进行原子薄GeSe的合成。GeSe片的厚度取决于剥离条件，并获得了高度结晶的4-10层堆叠的多层GeSe片，其横向尺寸超过200 nm。在环境大气中，沉积在基材上的LPE片材表现出强大的抗降解性，而乙醇分散液则以中等速率分解为元素Ge和Se纳米结构。密度泛函理论计算以及光学特性证实了GeSe片的蓝移带隙是强量子限制效应的结果。此外，我们显示出具有良好光学带隙的几层GeSe片材可基于光电化学电池有效收集太阳光，以产生光电流。我们的联合理论和实验结果表明，原子厚度的GeSe片可能是一种新型的二维半导体，可以用于光电子学和光子学中的潜在应用。