基于石墨烯-过渡金属硫属化物二维异质结的制备及器件界面研究

The layered structures of two dimensional (2D) materials, such as graphene, as well as the low lattice mismatch between various 2D materials make them ideal templates for the artificial construction of vertical and lateral heterojunctions. However, compared with the well-controlled growth process of one single kind of 2D materials, the creating of large-scale homogeneous vertical or lateral 2D heterostructures by the van der Waals stacking or covalently bonded stitching of 2D layered materials, is of great challenge, since the growth window of heterostructures is more fine and narrow as well as its extremely high sensitivity to the environmental interface. Thus, developing/optimizing new growth technologies, as well as realizing the interface regulations and device applications, is highly demanded. In view of this, the project aims to systematically study: ①how to use/optimize our developed growth technologies (including CVD and electrochemical deposition methods) to synthesize 2D lateral and vertical heterostructures based on graphene and transition metal dichalcogenides (TMDs); ② how to in-situ characterize and control the built-in potential within the lateral heterostructures based on TMDs by adoping the KPFM (Kelvin probe force microscopy) experiments;③how to design the new passive gas sensors based on the two Schottky junctions within the graphene/TMDs/graphene multi-vertical heterostructures without the objective limitations of the method of mechanical exfoliation. Therefore, the lunch of this project is of great significance to promote the synthesis technologies of the artificial heterostructures as well as the development of their interface regulations and application devices. In the end, this project will lay a solid foundation for the practical applications of the 2D heterostructures.

石墨烯为代表的二维材料，以其层状特性和较低的晶格失配，为人工构建异质结提供了有利平台。然而，相比单种二维材料较为可控的生长流程，异质结的生长窗口更为精细与狭窄，对其所处环境界面有着极高灵敏度，如何开发与优化制备技术，并实现异质结的界面调控与器件应用，是一巨大挑战。鉴于此，本项目拟开展如下研究：①结合化学气相沉积(CVD)与电镀方案等已有科研基础，实现基于石墨烯，过渡金属硫属化物(TMDs)平面与垂直异质结的制备与优化；②设计开尔文探针力显微镜(KFPM)实验，原位表征与调控TMDs平面异质结过渡区界面的内建电势；③构建石墨烯/TMDs/石墨烯的多结垂直异质结，突破机械剥离手段的客观限制，利用其双肖特基结性质实现新型无源气体传感器。本项目的开展对推动二维异质结的生长、界面研究以及应用器件的研制具有十分重要的现实意义，能够为二维层状材料异质结的实际应用奠定基础。

二维层状材料及其垂直与平面异质结，以其独特的物理性质为材料工程和器件设计提供了新维度，在电子学与光子学领域具有广泛应用前景。本项目的主要研究内容如下：.首先，我们使用商用喷墨打印机，在皮克(10−12g)量级对 过渡金属硫属化物（TMDs）的水基前驱体实现了稳定控制，并通过精确调控喷墨打印参数与快速加热过程，实现了大面积，厘米尺寸，具有良好厚度可控性的图案化TMDs薄膜以及其垂直与平面异质结的制备，并且可在30秒内合成毫米级的高质量单层TMDs。制备出的单层MoS2和MoSe2表现出了优异的电学性能，其载流子迁移率分别高达21和54cm2V-1s-1。.其次，我们发展了一种可控的H2等离子体方案来逐步合成Janus MoSH单分子层，在经过飞行时间二次离子质谱仪（TOF-SIMS）原位分析以及随后MoSSe的硒化过程中，证实了该MoSH的成功制备。我们采用场效应晶体管（FET）器件测试、开尔文探针力显微镜（KPFM）和密度泛函理论（DFT）计算相结合的方法，系统地研究了MoSH的电子性质，包括其高本征载流子浓度（∼2×1013cm-2）和费米能级（∼−4.11eV）。.再则，我们使用拥有两项授权专利的电化学沉积（ECD）技术，制备出 WS2/石墨烯异质结，并观察到扭曲的WS2薄膜（~15.6°）。基于该异质结的光电探测器，其光响应率高达2.62A/W，响应时间为49ms。通过KPFM表征和I–V的温度特性研究，我们定量了WS2/石墨烯异质结中的肖特基势垒（ϕSB=310mV）和内建电势（ϕBi=270mV），该测量结果与DFT计算吻合。.最后，我们研究了单层MoS2-WS2平面异质结中的栅极可调特性。通过结合使用KPFM和I–V特性测试，我们发现，当Vg=40V时，内建电势可高达262meV的，这一现象可用我们提出的晶格缺陷机制来解释。同时，基于异质结能带不连续模型，我们给出了二维Ⅱ型n-n异质结的能带图。.本项目在Advanced Materials， ACS Nano 等杂志上发表SCI论文9篇，其中,中科院一区论文4篇，影响因子大于10的2篇，项目开展期间，申请发明专利4项，其中授权2项。