School of Physics, Southeast University, Nanjing 211189, China.
Nanoscale. 2018 Jul 5;10(25):12180-12186. doi: 10.1039/c8nr01533c.
Gallium selenide (GaSe) has recently emerged as a unique platform due to its exciting properties, namely, large and fast photo-response, high carrier mobility and non-linear optical properties. However, exposure for a few days causes the fast oxidation of ultrathin GaSe under ambient conditions and the oxidation mechanism remains unclear. By means of density functional theory calculations and ab initio molecular dynamics simulations, we comprehensively investigated the possible sources that cause oxidation of ultrathin GaSe. Our results show that illumination and Se vacancies induce the fast oxidation of GaSe. Under illumination, photo-excited electrons from the surface of GaSe are effectively transferred to oxygen molecules and thus, superoxide anions (O2-) are generated that react with GaSe. Moreover, Se vacancies directly react with O2. In both the cases, the Ga-Se bonds are continually replaced by Ga-O bonds, which eventually leads to complete degradation of GaSe, accompanied with the formation of the oxidation products Ga2O3 and elemental Se. The comprehensive degradation mechanism unveiled herein lays an important foundation for the development of suitable protecting strategies in GaSe-based devices.
硒化镓（GaSe）由于其独特的性质，如大而快速的光响应、高载流子迁移率和非线性光学性质，最近成为一个独特的平台。然而，在环境条件下，超薄 GaSe 在暴露数天后会快速氧化，其氧化机制仍不清楚。通过密度泛函理论计算和从头分子动力学模拟，我们全面研究了导致超薄 GaSe 氧化的可能来源。研究结果表明，光照和硒空位会导致 GaSe 的快速氧化。在光照下，GaSe 表面的光激电子有效地转移到氧分子上，从而产生超氧阴离子（O2-），与 GaSe 发生反应。此外，硒空位直接与 O2 反应。在这两种情况下，Ga-Se 键不断被 Ga-O 键取代，最终导致 GaSe 完全降解，同时生成氧化产物 Ga2O3 和元素硒。本研究揭示的全面降解机制为基于 GaSe 的器件中开发合适的保护策略奠定了重要基础。
