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

随着器件继续小型化，下一代电子技术的进步需要在材料、功能甚至器件操作模式上取得突破，以应对热管理和电荷隧道等挑战。作为一种单原子厚度的导体，石墨烯最近引起了极大的兴奋，它具有特殊的电子性质，具有特别高的电子迁移率，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，形成计算设备基础的数字电子实现是困难的。磷烯是一种单层或几层黑色磷，是一种稳定的层状磷同素异形体，具有像石墨烯一样高度可移动的电子，但也像硅一样是一种半导体。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，而且由于磷与空气发生反应，器件钝化是重要的。这项研究旨在研究器件钝化以及磷烯的基本性质，以实现新型的、高性能的电子和光电子器件。该项目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队伍。通过向当地高中生和教师伸出援手，这项计划也将对内陆帝国种族多元化的当地社区产生积极影响。这项计划的目标是研究单层或几层黑磷的电子、热学和热电性质，并探索基于这种新材料的新型器件。由于具有很高的体迁移率、面内各向异性、预期的大热电功率和可在很大范围内通过应变或厚度调节的直接带隙等许多理想的性质，膦已经成为一种很有前途的电子和光学应用材料。然而，诸如迁移率瓶颈和主要散射机制等基本特性尚不清楚，器件钝化仍然很重要。我们的研究方法包括(1)。通过封装制造稳定的高迁移率器件，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来调整器件性能，(3)。各向异性塞贝克系数和能斯特功率的热电势测量；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的磷烯双层。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的基础上，例如前所未有的4000 cm2/vs的迁移率和对磷烯中量子振荡的观察。这项研究的成果包括阐明了单层和少层磷烯的基本材料性质，并为稳定、高迁移率器件提供了急需的途径，而各向异性热电层、pn结和扭曲双层膜的探索将为新的电子、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.