Aftab Sikandar, Yousuf Saqlain, Khan Muhammad Usman, Khawar Rafia, Younus Ayesha, Manzoor Mumtaz, Iqbal Muhammad Waqas, Iqbal Muhammad Zahir
Department of Physics & Astronomy and Graphene Research Institute, Sejong University, Seoul 05006, Korea.
Nanoscale. 2020 Aug 7;12(29):15687-15696. doi: 10.1039/d0nr03904g. Epub 2020 Jul 16.
Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are layered semiconductor materials that have recently emerged as promising candidates for advanced nano- and photoelectronic applications. Previously, various doping methods, such as surface functionalization, chemical doping, substitutional doping, surface charge transfer, and electrostatic doping, have been introduced, but they are not stable or efficient. In this study, we have developed carrier polarity modulation of molybdenum ditelluride (MoTe) for the development of phototransistors and switching photodiodes. Initially, we treated p-MoTe in a N environment under DUV irradiation and found that the p-type MoTe changed to n-type MoTe. However, the treated devices exhibited environmental stability over a long period of 60 days. Kelvin probe force microscopy (KPFM) measurements demonstrated that the values of the work function for p-MoTe and n-MoTe were ∼4.90 and ∼4.49 eV, respectively, which confirmed the carrier tunability. Also, first-principles studies were performed to confirm the n-type carrier polarity variation. Interestingly, the n-type MoTe reversed its polarity to p-type after the irradiation of the devices under DUV in an O environment. Additionally, a lateral homojunction-based p-n diode of MoTe with a rectification ratio of ∼2.5 × 10 was formed with the value of contact potential difference of ∼400 mV and an estimated fast rise time of 29 ms and decay time of 38 ms. Furthermore, a well self-biased photovoltaic behavior upon illumination of light was achieved and various photovoltaic parameters were examined. Also, V switching behavior was established at the p-n diode state by switching on and off the incident light. We believe that this efficient and facile carrier polarity modulation technique may pave the way for the development of phototransistors and switching photodiodes in advanced nanotechnology.
二维（2D）过渡金属二硫属化物（TMDs）是一类层状半导体材料，最近已成为先进的纳米和光电子应用中很有前景的候选材料。此前，人们已经引入了各种掺杂方法，如表面功能化、化学掺杂、替代掺杂、表面电荷转移和静电掺杂，但这些方法不稳定或效率不高。在本研究中，我们开发了用于制备光电晶体管和开关光电二极管的碲化钼（MoTe₂）载流子极性调制方法。最初，我们在深紫外（DUV）照射下于氮气环境中处理p型MoTe₂，发现p型MoTe₂转变为n型MoTe₂。然而，经过处理的器件在长达60天的时间内表现出环境稳定性。开尔文探针力显微镜（KPFM）测量表明，p型MoTe₂和n型MoTe₂的功函数值分别约为4.90和4.49 eV，这证实了载流子的可调性。此外，还进行了第一性原理研究以确认n型载流子极性变化。有趣的是，在氧气环境中对器件进行DUV照射后，n型MoTe₂的极性又反转回p型。此外，形成了基于横向同质结的MoTe₂ p-n二极管，其整流比约为2.5×10，接触电势差约为400 mV，估计快速上升时间为29 ms，衰减时间为38 ms。此外，在光照下实现了良好的自偏置光伏行为，并对各种光伏参数进行了研究。而且，通过打开和关闭入射光，在p-n二极管状态下建立了V开关行为。我们相信，这种高效且简便的载流子极性调制技术可能为先进纳米技术中光电晶体管和开关光电二极管的发展铺平道路。
