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

下一代电子技术的进步需要在材料、功能甚至设备操作范式方面取得突破，以应对随着设备不断小型化，热管理和电荷隧道等挑战。石墨烯作为一种单原子厚度的导体，具有特殊的电子特性，特别是高迁移率的电子，最近引起了极大的兴奋，2010年诺贝尔物理学奖被授予了这种材料的开创性工作。然而，由于石墨烯不是半导体，形成计算设备基础的数字电子实现是困难的。磷烯是一种单层或多层的黑磷，是一种稳定的层状磷同素异形体，它像石墨烯一样具有高度可移动的电子，但也像硅一样是一种半导体。这可能使它成为数字电子学和逻辑门的基础。然而，它的许多基本性质是未知的，因为磷与空气反应，设备钝化是重要的。本研究旨在研究器件的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子器件。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，包括那些来自代表性不足的群体的学生，并帮助维持美国技术部门急需的科学家和工程师的管道。通过向当地高中学生和教师推广，该项目还将对内陆帝国地区的多种族社区产生积极影响。本提案的目标是研究单层或多层黑磷或磷烯的电子，热学和热电性质，并探索基于这种新材料的新型器件。由于其许多理想的特性，如非常高的体迁移率、面内各向异性、预期的大热电功率和可在大范围内通过应变或厚度调节的直接带隙，磷烯已成为电子和光学应用的有前途的材料。然而，诸如迁移瓶颈和主要散射机制等基本性质尚不清楚，器件钝化仍然很重要。我们的方法包括：(1)通过封装制造稳定、高迁移率的器件，并通过控制衬底、保护层和肖特基势垒进行优化；(2)通过离子液体门控和各向同性或各向异性应变调谐器件特性；(3)各向异性塞贝克系数和能司特功率的热功率测量；(4).空间调制器件，如用于电子、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双分子层。该项目建立在PI和co-PI在石墨烯和碳纳米管方面的良好记录之上，以及令人兴奋的初步数据，如前所未有的4000 cm2/ v的迁移率和对磷烯量子振荡的观察。本研究的成果包括阐明单层和多层磷烯的基本材料性质，为稳定的高迁移率器件提供急需的途径，而探索各向异性热电、pn结和扭曲双层将为新的电子、热电和光电子应用打开大门。

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.