In this work we investigate the effects of ambient exposure on CVD grown PdSe₂ and correlate density functional theory calculations of various physisorption and chemisorption binding energies and band structures to the observed changes in the electrical transport. Pristine PdSe₂ is n-type due to intrinsic selenium vacancies, but shows increased p-type conduction and decreased n-type conduction as a function of ambient aging during which various aging mechanisms appear to be operative. Short term aging (<160 h) is ascribed to an activated chemisorption of molecular O₂ at selenium vacancies; first-principles calculations suggest a ~0.85 eV activation energy and adsorption geometries with binding energies varying between 1.3–1.6 eV, in agreement with experimental results. Importantly, this chemisorption is reversible with a low temperature anneal. At long term aging (>430 h), there is a total suppression of n-type conduction, which is attributed to a dissociative adsorption/reaction of the O₂ molecules to atomic O and subsequent PdO₂ formation. XPS confirms the presence of PdO₂ in long term aged flakes. At these extended aging times, the low temperature anneal restores low n-type conduction and suppresses p-type conduction due to the low thermal stability of PdO₂ which, in agreement with XPS measurements, sublimates during the anneal. Thus PdSe₂ devices can be processed into device architectures in standard laboratory environments if atmospheric exposure times are limited to on the order of 1 week.

在这项工作中，我们研究了环境暴露对CVD生长的PdSe ₂的影响，并使各种物理吸附和化学吸附结合能以及能带结构的密度泛函理论计算与电传输中观察到的变化相关。原始的PdSe ₂由于固有的硒空位而为n型，但是随着环境老化的作用，p型导电性增加，n型导电性减小，在此期间各种老化机制似乎都起作用。短期老化（<160小时）归因于分子O ₂的活化化学吸附硒空缺；第一性原理计算表明，约0.85 eV的活化能和结合能在1.3-1.6 eV之间变化的吸附几何形状与实验结果一致。重要的是，这种化学吸附在低温退火下是可逆的。在长期老化（> 430小时）时，完全抑制了n型传导，这归因于O ₂分子对原子O的解离吸附/反应以及随后的PdO ₂形成。XPS证实了长期老化的薄片中存在PdO ₂。在这些延长的老化时间下，由于PdO _2的低热稳定性，低温退火可恢复低n型导通并抑制p型导通与XPS测量结果一致，在退火过程中会升华。因此，如果大气暴露时间限制在1周左右，则可以在标准实验室环境中将PdSe ₂器件处理为器件架构。