5-25. Investigation the electronic property of two dimensional semiconductors by scanning probe technique

Zegao Wang

School of materials science and engineering, sichuan university

Abstract: Compared to zero-bandgap graphene, 2D layered transition metal dichalcogenides (TMDs) with the chemical formula MX₂ (where M=group IVB-VIIB metal and X=chalcogen) have brought new possibility for the applications in ultralow-power electronics due to the reasonable bandgap. Currently, the carrier mobilities of TMDs at ambient conditions are a little bit low which limit their practical applications. Besides synthesizing new 2D layered materials, revealing the transport mechanism and further optimizing the device configuration are acknowledged as another promising strategy.

In this talk, we will introduce the recent progress of the investigation of device mechanism with scanning probe technique including electric field microscopy, kelvin probe force microscopy and current atomic force microscopy. With electric field microscopy, the effective surface potential of 1-40 layers WSe₂ has been studied to understand the screening effect. Combined the scanning probe technique with the electronic device, we are able to study the electronic property of materials as well as the device performance, and demonstrating that the Fermi level of WSe₂ would shift by 440 meV when the WSe₂ switch between n-type semiconductor and p-type semiconductor. We have proposed a green method to controllably create one-dimension nanochannel, two-dimensional pit and three-dimensional cavity on MoS₂ basal plane which effectively improve the surface activity. The PtSe₂ nanosheets have been synthesized and the growth mechanism has been studied in detail. By fabricating the PtSe₂ transistor with short channel length, we have demonstrated that the PtSe₂ shows p-type transport property. The PtSe₂/MoS₂ p-n junctions have been constructed with excellent diode performance indicating its potential application in two dimensional nano-devices. In a word, with the scanning probe technique, we are able to understand the local electronic property of 2D layered semiconductor, such as surface potential, work function et al. Significantly, combining the device and scanning probe technique, we first in-situ revel how the electronic structure of semiconductor evolution with device performance switching among p-type, institutor and n-type.

Keywords: Electronic materials; Scanning probe microscopy; Electrical property; Growth mechanism

利用扫描探针技术研究二维半导体材料电学性质

王泽高

四川大学材料科学与工程学院，成都，中国，610065

摘要：与零带隙石墨烯相比，具有MX₂化学式的二维层状过渡金属二硫化物（Transition Metal Dichalcogenides, TMD）（其中M表示IVB-VIIB族金属，X表示硫族元素）因具有优异的带隙结构（覆盖了0~2.5eV）而为超低功耗电子器件的应用带来了新的可能性。目前，在大气环境中，TMD材料的性能偏低，如载流子迁移率相对偏低，这限制了它们的实际应用。

在本报告中，作者将介绍扫描探针技术，包括电场力显微镜，开尔文探针力显微镜和导电原子力显微镜在二维层状半导体研究中的作用，特别侧重于其电学性质研究^[1-3]。利用电场力显微镜，通过研究1~40层二硒化钨半导体对基底表面电荷的屏蔽效应揭示了二维层状半导体的界面屏蔽机理。开发了一种元器件显微分析技术，将元器件与开尔文力显微镜相结合，原位研究了器件性质与材料电子结构的关联，发现作为双极性半导体的二硒化钨，其费米能级随着载流子浓度的改变可以上下移动440 meV，直观的证实了双极性导电的机制。提出了一种绿色刻蚀二维材料basal面的方法，通过调节反应温度计气氛，可控的在basal面构建了一维纳米通道、二维面内缺陷以及三维洞，并证实了其zigzag-S的晶相边缘结构。通过加工microcell，定量的测量了这些纳米结构对材料表面活性的贡献。首次合成了二硒化铂纳米片，通过调节反应温度、组分等优化二硒化铂合成工艺获得高质量二硒化铂纳米片；通过构建短沟道二硒化铂纳米电子器件揭示了其p型半导体导电机制，并构建了二硒化铂/二硫化钼垂直异质结二节管，研究了其整流特性为进一步研制新型二维材料及器件提供了参考。