Tin diselenide (SnSe₂) is a van der Waals semiconductor, which spontaneously forms a subnanometric SnO₂ skin once exposed to air. Here, by means of surface-science spectroscopies and density functional theory, we have investigated the charge redistribution at the SnO₂–SnSe₂ heterojunction in both oxidative and humid environments. Explicitly, we find that the work function of the pristine SnSe₂ surface increases by 0.23 and 0.40 eV upon exposure to O₂ and air, respectively, with a charge transfer reaching 0.56 e^–/SnO₂ between the underlying SnSe₂ and the SnO₂ skin. Remarkably, both pristine SnSe₂ and defective SnSe₂ display chemical inertness toward water, in contrast to other metal chalcogenides. Conversely, the SnO₂–SnSe₂ interface formed upon surface oxidation is highly reactive toward water, with subsequent implications for SnSe₂-based devices working in ambient humidity, including chemical sensors. Our findings also imply that recent reports on humidity sensing with SnSe₂ should be reinterpreted, considering the pivotal role of the oxide skin in the interaction with water molecules.

中文翻译：

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暴露于氧化和潮湿环境的 SnSe2 表面的电荷重新分布机制及其对化学传感的相关影响


二硒化锡 (SnSe ₂ ) 是一种范德华半导体，一旦暴露于空气中，就会自发形成亚纳米 SnO ₂皮层。在这里，通过表面科学光谱和密度泛函理论，我们研究了氧化和潮湿环境中 SnO ₂ -SnSe ₂异质结的电荷重新分布。明确地，我们发现原始 SnSe ₂表面的功函数在暴露于 O ₂和空气时分别增加了 0.23 和 0.40 eV，底层 SnSe ₂和 SnO ₂之间的电荷转移达到 0.56 e ^– /SnO ₂皮肤。值得注意的是，与其他金属硫属化物相比，原始 SnSe ₂和有缺陷的 SnSe ₂对水都表现出化学惰性。相反，表面氧化时形成的SnO ₂ -SnSe ₂界面对水具有高度反应性，这对在环境湿度下工作的基于SnSe ₂的器件（包括化学传感器）产生了后续影响。我们的研究结果还意味着，考虑到氧化皮在与水分子相互作用中的关键作用，最近关于 SnSe ₂湿度传感的报道应该重新解释。