Buried Single Crystal Semi-Metal/Semiconductor Nanocomposites for 3D Electronic Materials

非技术描述：该项目研究一类新的晶态金属-半导体纳米结构复合材料。由于其独特的三维(3D)纳米结构，这些纳米复合材料具有潜在的实际应用潜力，使新的半导体器件、热电、光电探测器和太赫兹技术具有广泛的社会影响。通过结合原子水平的生长控制和结构和电子表征，研究了这些3D纳米结构复合材料的形成机理。生长条件的改变，如金属与半导体成分的比例、生长温度、具有不同晶体取向的衬底以及不同的金属-半导体组合，导致了具有不同性质的新的纳米结构。这些参数对生长的影响被模型化，然后用于设计新材料。这项研究涉及材料科学、电气工程、凝聚态物质和材料物理以及化学等跨学科研究领域的研究生和博士后助理。此外，该项目的参与者参与了从高中到研究生及以后的各种教育活动，使所有年龄段的人和代表性不足的社区接触到STEM机会。技术描述：该项目的主要目标是建立对分子束外延(MBE)生长GaSb、GaAs和相关化合物半导体与共沉积稀土元素(如Er)过程中发生的表面介导热力学相分离机制的基本理解。分子束外延共沉积导致了嵌入的外延半金属稀土钒棒、树枝和二维片的形成。进一步的研究包括确定这些纳米结构的物理性质，并探索它们作为光电探测器中埋入触点的潜在应用。采用扫描隧道显微镜、光谱学和X射线光电子能谱等原子级原位结构、化学和电子表征手段，结合分子束外延生长，从原子尺度上研究了分子束外延的生长机理。用变温磁输运、光致发光和太赫兹(THz)光谱研究了薄膜的电学和光学性质。对这些纳米结构材料的基础材料探索可能使其在未来的应用中成为叠层光电探测器和太赫兹偏振滤光片、探测器和光源的掩埋接触。

Nontechnical Description: This project investigates a new class of crystalline metal-semiconductor nanostructure composites. Because of their unique 3-dimensional (3D) nanostructures, these nanocomposite materials have the potential for practical applications for enabling new semiconductor devices, thermoelectrics, photodetectors, and terahertz technologies with broad impacts to society. The mechanism by which these 3D nanostructure composites form is studied by combining atomic-level control of growth with structural and electronic characterization. Changes in growth conditions, such as the proportion of metal to semiconductor components, the growth temperature, substrates with various crystal orientations, and different metal-semiconductor combinations, result in new nanostructures with different properties. The effects of these parameters on growth are modeled and then used to design new materials. This research involves graduate students and postdoctoral associates in interdisciplinary research areas of materials science, electrical engineering, condensed matter and materials physics, and chemistry. In addition, participants of this project are engaged in a variety of educational activities from high-school through graduate level and beyond, which brings people of all ages and under-represented communities into contact with STEM opportunities. Technical Description: The main objective of the project is to establish a fundamental understanding of a surface mediated thermodynamic phase separation mechanism that occurs during the molecular beam epitaxial (MBE) growth of GaSb, GaAs and related compound semiconductors with co-deposition of a rare-earth (RE) element such as Er. The MBE co-deposition results in the formation of embedded epitaxial semi-metallic RE-V rods, branched trees and two-dimensional sheets. Further study includes determining the physical properties of these nanostructures and exploring their potential applications as buried contacts in photodetectors. In-situ atomic level structural, chemical and electronic characterization tools, including scanning tunneling microscopy and spectroscopy plus X-ray photoelectron spectroscopy, are combined with MBE growth to study the growth mechanism at the atomic scale. The electronic and optical properties are studied ex-situ by temperature-dependent magnetotransport, photoluminescence and terahertz (THz) spectroscopy. The fundamental materials exploration of these nanostructured materials could enable future applications as buried contacts for stacked photodetectors and terahertz polarization filters, detectors, and sources.