Electronic and Thermoelectric Properties of High Mobility Few-Layer Phospherene Devices

下一代电子产品的发展需要在材料、功能甚至器件操作模式方面取得突破，以应对随着器件不断小型化而出现的热管理和电荷隧穿等挑战。石墨烯最近作为一种单原子厚的导体产生了很大的兴奋，具有特殊的电子特性，特别是高迁移率的电子，2010年诺贝尔物理学奖被授予这种材料的开创性工作。然而，由于石墨烯不是半导体，数字电子实现（诸如形成计算设备的基础的那些）是困难的。磷烯是一种单层或几层黑磷，是一种稳定的层状磷同素异形体，像石墨烯一样具有高度移动的电子，但也是一种像硅一样的半导体。这可能使其成为数字电子和逻辑门的基础。然而，它的许多基本性质是未知的，因为磷与空气反应，设备钝化是很重要的。该研究旨在研究器件钝化以及磷烯的基本性质，以实现新型，高性能的电子和光电器件。该计划将通过半导体和材料研究整合本科生和研究生的招聘和教育，包括来自代表性不足群体的学生，并帮助维持美国技术部门急需的科学家和工程师管道。该项目的目标是研究单层或多层黑磷或磷烯的电子、热和热电性质，并探索基于这种新材料的新型器件。磷已成为一种有前途的材料，用于电子和光学应用，由于其许多理想的性能，如非常高的体迁移率，面内各向异性，预期的大热电功率和直接带隙，可调的应变或厚度在很大范围内。然而，基本属性，如流动性瓶颈和主要的散射机制是未知的，器件钝化仍然很重要。我们的方法包括（1）。通过封装和通过控制衬底、保护层和肖特基势垒的优化来制造稳定的高迁移率器件;通过离子液体门控和各向同性或各向异性应变调节器件性质，（3）。各向异性塞贝克系数和能斯特功率的热功率测量;（4）。空间调制器件，例如用于电子学、电致发光和光伏应用的PN结，以及用于周期性带隙调制的扭曲磷烯双层。该计划建立在PI和co-PI在石墨烯和碳纳米管方面的良好记录以及令人兴奋的初步数据之上，例如前所未有的4000 cm 2/Vs的迁移率和磷烯量子振荡的观察。这项研究的成果包括阐明单层和少层磷烯的基本材料特性，并为稳定的高迁移率器件提供急需的途径，而各向异性热电，pn结和扭曲双层的探索将为新型电子，热电和光电应用打开大门。

The advancement of next generation electronics requires breakthroughs in materials, functionalities and even device operation paradigms, in order to address challenges such as thermal management and charge tunneling as devices continue to be miniaturized. Graphene has recently generated a great deal of excitement as a one-atom thick conductor with exceptional electronic properties with especially high mobility electrons, with the 2010 Physics Nobel prize being awarded for groundbreaking work on this material. However, as graphene is not a semiconductor, digital electronics realizations such as those forming the basis of computing devices are difficult. Phosphorene, a single or few layers of black phosphorus, a stable layered phosphorus allotrope, has highly mobile electrons like graphene but is also a semiconductor like silicon. This potentially enables it to form the basis for digital electronics and logic gates. However, many of its basic properties are unknown and, since phosphorus reacts with air, device passivation is important. The proposed research aims to investigate device passivation, as well the fundamental properties of phosphorene, with the goal of realizing novel, high performance electronic and optoelectronic devices. The program will integrate the recruitment and education of undergraduate and graduate students, including those from under-represented groups, via semiconductor and materials research, and help to maintain the much-need pipeline of scientists and engineers for American technological sector. By outreaching to local high school students and teachers, this program will also positively impact the ethnically diverse local communities in Inland Empire.The goal of this proposal is to investigate electronic, thermal and thermoelectric properties of mono- or few-layer black phosphorus, or phosphorene, and explore novel devices based on this new material. Phosphorene has emerged as a promising material for electronics and optical applications, due to its many desirable properties such as very high bulk mobility, in-plane anisotropy, expected large thermoelectric power and a direct band gap that is tunable by strain or thickness over a large range. However, basic properties such as the mobility bottleneck and major scattering mechanisms are not known and device passivation remains important. Our approaches include (1). fabrication of stable, high mobility devices by encapsulation, and optimization via control of substrate, protection layers, and Schottky barrier; (2). tuning device properties via ionic liquid gating and isotropic or anisotropic strain, (3). thermopower measurements of anisotropic Seebeck coefficients and Nernst power; (4). spatially modulated devices such as pn junctions for electronics, electroluminescence and photovoltaic applications, and twisted phosphorene bilayers for periodic band gap modulation. This program builds on the PI's and co-PI's strong track records on graphene and carbon nanotubes, and exciting preliminary data such as unprecedented mobility of 4000 cm2/Vs and observation of quantum oscillations in phosphorene. Outcomes of this research include elucidation of the fundamental material properties of single- and few-layer phosphorene, and providing the much-needed route for stable, high mobility devices, while exploration of anisotropic thermopower, pn junctions and twisted bilayers will open the door for novel electronic, thermoelectric and optoelectronic applications.