Transition Metal Doping in Two-Dimensional, Atomically Thin Semiconductors

摘要：非技术：通过杂质掺杂控制半导体中的电输运已经实现了整整一代技术。随着器件长度尺度的缩小，推动了硅技术的极限，新的原子薄半导体材料，如二维过渡金属二硫族化合物，正在成为硅的潜在替代品。虽然硅技术的掺杂控制已经完善了几十年，但原子薄过渡金属二硫族化合物的受控合成和掺杂策略仍处于起步阶段。在这个项目中，研究人员提出了一种稳定的掺杂策略，该策略涉及用杂质金属取代过渡金属原子。研究人员打算用这种方法证明空穴和电子掺杂是如何成为可能的。这项工作可以实现过渡金属二硫化物纳米片的可控和稳定掺杂，以调整其载流子类型和密度，从而为由原子薄半导体构建的下一代电子和光电子器件铺平道路。为了整合研究和教学，研究人员提出了专门设计的互动学习模块（虚拟实验室），它将被整合到伦斯勒理工学院的课程中。外联活动包括向当地高中的学生和教师展示互动模块；这将有助于普及科学，并吸引代表性不足的群体从事科学和工程事业。技术描述：在原子级薄的过渡金属二硫族化合物中，很少有直接取代（掺杂）过渡金属原子的报道。这可能是由于过渡金属原子远比硫原子稳定，因此更难被取代。然而，研究人员的初步结果表明，在化学气相沉积生长过程中，单层过渡金属二硫族化合物的大面积（原位）过渡金属掺杂确实是可能的。在这个项目中，研究人员提出了在广泛的掺杂浓度下的第一性原理密度泛函理论计算，以了解过渡金属掺杂如何影响这些材料的半导体和光电子性能。在实验方面，研究人员建议证明兴奋剂可以在大范围内系统地调节。使用背门控场效应晶体管配置的变温度电子输运测量将被执行，以确定材料的电子特性如何受到掺杂的影响。此外，将在广泛的温度和掺杂浓度范围内进行光致发光和微分反射光谱，以了解掺杂如何影响材料的光电性能。该项目最终将以原子尖锐pn结装置为特色的技术演示。为了完成上述任务，研究人员组建了一个具有互补专业知识的跨学科团队。实验家和理论家之间的合作将使团队能够深入了解潜在的物理原理，并在可控和稳定地掺杂原子薄过渡金属二硫族化物材料方面取得快速进展。

Abstract:Non-Technical:Controlling electrical transport in semiconductors by impurity doping has enabled an entire generation of technology. As device length scales shrink, pushing the limits of silicon technology, new atomically thin semi-conducting materials such as two-dimensional transition metal dichalcogenides are emerging as a potential replacement to silicon. While doping control has been perfected for silicon technology over many decades, controlled synthesis and doping strategies for atomically thin transition metal dichalcogenides are still in their infancy. In this project, the investigators propose to demonstrate a stable doping strategy for such materials which involves substitution of the transition metal atom by an impurity metal. The investigators propose to show how both hole and electron doping is possible using such an approach. This work could enable controllable and stable doping of transition metal dichalcogenide nanosheets to tune their carrier type and density, thereby paving the way for next generation electronic and optoelectronic devices constructed from atomically-thin semiconductors. To integrate research and teaching, the investigators propose specially designed interactive learning modules (virtual labs) which will be integrated into the curriculum at the Rensselaer Polytechnic Institute. Outreach includes demonstrations of the interactive modules to students and teachers from local area high schools; this will help to popularize science and attract underrepresented groups to careers in science and engineering.Technical Description:There are very few reports of direct substitution (doping) of transition metal atoms in atomically-thin transition metal dichalcogenides. This is likely due to the fact that transition metal atoms are far more stable than chalcogens and hence much harder to replace. However initial results by the investigators indicate that large-area (in situ) transition metal doping for monolayer transition metal dichalcogenides is indeed possible during the chemical vapor deposition growth process. In this project, the investigators propose first-principles density functional theory calculations over a wide range of doping concentrations to understand how the semiconducting and optoelectronic properties of such materials are affected by transition metal doping. On the experimental side, the investigators propose to demonstrate that the doping can be systematically tuned over a wide range. Variable temperature electronic transport measurements, using a back gated field-effect transistor configuration will be performed to establish how the material's electronic properties are influenced by doping. Further, photoluminescence and differential reflectance spectroscopy over a wide range of temperatures and dopant concentrations will be carried out to understand how doping affects the optoelectronic properties of the material. The project will culminate in a technology demonstration featuring an atomically sharp p-n junction device. To accomplish the above tasks, the investigators have assembled an interdisciplinary team with complementary expertise. Collaboration between experimentalists and a theorist will enable the team to develop an in-depth understanding of the underlying physics and make rapid progress towards controllably and stably doping atomically-thin transition metal dichalcogenide materials.