Department of Physics, National Taiwan University, Taipei 106, Taiwan.
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
Sci Rep. 2017 Mar 21;7:44768. doi: 10.1038/srep44768.
Two-dimensional (2D) materials are composed of atomically thin crystals with an enormous surface-to-volume ratio, and their physical properties can be easily subjected to the change of the chemical environment. Encapsulation with other layered materials, such as hexagonal boron nitride, is a common practice; however, this approach often requires inextricable fabrication processes. Alternatively, it is intriguing to explore methods to control transport properties in the circumstance of no encapsulated layer. This is very challenging because of the ubiquitous presence of adsorbents, which can lead to charged-impurity scattering sites, charge traps, and recombination centers. Here, we show that the short-circuit photocurrent originated from the built-in electric field at the MoS junction is surprisingly insensitive to the gaseous environment over the range from a vacuum of 1 × 10 Torr to ambient condition. The environmental insensitivity of the short-circuit photocurrent is attributed to the characteristic of the diffusion current that is associated with the gradient of carrier density. Conversely, the photocurrent with bias exhibits typical persistent photoconductivity and greatly depends on the gaseous environment. The observation of environment-insensitive short-circuit photocurrent demonstrates an alternative method to design device structure for 2D-material-based optoelectronic applications.
二维（2D）材料由原子级薄的晶体组成，具有巨大的表面积与体积比，其物理性质很容易受到化学环境变化的影响。与其他层状材料（如六方氮化硼）封装是一种常见的做法；然而，这种方法通常需要复杂的制造工艺。另一方面，探索在没有封装层的情况下控制传输特性的方法是很有趣的。由于无处不在的吸附剂，这是非常具有挑战性的，因为它们会导致带电杂质散射位点、电荷陷阱和复合中心。在这里，我们表明，在从 1×10-1 托真空到环境条件的范围内，源自 MoS 结内置电场的短路光电流对气体环境出人意料地不敏感。短路光电流的环境不敏感性归因于与载流子密度梯度相关的扩散电流的特性。相反，具有偏置的光电流表现出典型的持续光导性，并且极大地取决于气体环境。对环境不敏感的短路光电流的观察为基于 2D 材料的光电应用的器件结构设计提供了一种替代方法。
