Tuning and protecting MoTe2 derived phase change materials for electronic device fabrication

调整和保护用于电子器件制造的 MoTe2 衍生相变材料

基本信息

批准号：
1608654
负责人：
Matthias Batzill
金额：
$ 29.67万
依托单位：
University of South Florida
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-07-15 至 2019-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1608654&HistoricalAwards=false
关键词：
Tuning protecting MoTe2 derived phase

项目摘要

Abstract: Growth, modification, and encapsulation of MoTe2 derived semiconductor-to-metal phase change materials for electronic device applications.Nontechnical: Layered semiconductors, with strong in-plane bonding and only weak, non-covalent interactions between planes, can be reduced to a single molecular layer thickness while maintaining good electronic properties. Thus these materials enable the ultimate reduction in length scale for microelectronic devices. MoTe2 is of particular interest in this class of novel semiconductors because of a desirable band-gap and importantly, the presence of a structural phase change that enables transforming the material from a semiconductor to a metal. Local switching of the phase of MoTe2 thus enables to make metal/semiconductor devices entirely build out of a single elemental composition. In this project we are aiming at overcoming materials engineering challenges and thus enabling utilization of the special phase change properties of MoTe2 in device structures. First, we will establish synthesis of single or few molecular layers of MoTe2 on a wafer scale. Second, we investigate the controlled phase transformation from the semiconducting to the metallic phase and investigate approaches to modify this phase transformation by addition of other elements. Third, we address the chemical instability of MoTe2, which leads to easy oxidation. Strategies to encapsulate it in a protective layer will be developed, which is essential for making MoTe2 useable for devices. This project is embedded in the research activity on two-dimensional materials at the University of South Florida and will provide education to graduate and undergraduate students in an area of future technological relevance. Technical: The van-der Waals semiconductor MoTe2 exhibits a relatively small band gap of about ~ 1eV and is a promising material for ambipolar field effect devices. The strong light absorption over the entire visible spectrum makes MoTe2 also interesting for photovoltaics and its band gap value makes it a candidate for near infrared optoelectronics. In addition, a thermally induced phase change of MoTe2 from semiconducting to metallic provides possible solutions to materials engineering problems of making electrical contacts to van der Waals semiconductors. In this project we will investigate and optimize the growth of MoTe2 by molecular beam epitaxy. Modification of MoTe2 by alloying will be studied with the goal of enabling tuning of the band gap as well as phase change behavior. The growth of these films and their properties are primarily characterized with scanning probe microscopy/spectroscopy and photoemission and thus we gain insights of the growth and phase transformation mechanisms at the nanoscale. One main shortcoming of MoTe2 is its relatively poor chemical stability, which causes its degradation under ambient conditions. To overcome this stability-issue the protection of these MoTe2-derived materials by oxide-capping layers will be studied. Phase change behavior with and without capping layer is compared, especially in view of the dependence of the transition temperature on Te-deficiency. Finally, in-plane interfaces between MoTe2 and dissimilar TMDs are fabricated with the aim of utilizing the phase change properties of MoTe2 for making ohmic-contacts to other TMD semiconductors. Thus this project will investigate if MoTe2 could be used as a universal material for addressing the general problem of making electrical contacts to two-dimensional van der Waals semiconductors.

摘要：用于电子器件应用的 MoTe2 衍生半导体-金属相变材料的生长、改性和封装。非技术：层状半导体具有强的面内键合，且平面之间只有微弱的非共价相互作用，可以简化为单分子层厚度，同时保持良好的电子性能。因此，这些材料能够最终减小微电子器件的长度尺寸。 MoTe2 在这类新型半导体中特别受关注，因为它具有理想的带隙，而且更重要的是，它存在结构相变，可以将材料从半导体转变为金属。因此，MoTe2 相的局部转换使得金属/半导体器件完全由单一元素组成构建而成。在这个项目中，我们的目标是克服材料工程挑战，从而能够在器件结构中利用 MoTe2 的特殊相变特性。首先，我们将在晶圆级上合成单层或少数 MoTe2 分子层。其次，我们研究了从半导体相到金属相的受控相变，并研究了通过添加其他元素来修改这种相变的方法。第三，我们解决了 MoTe2 的化学不稳定性，这导致容易氧化。将开发将其封装在保护层中的策略，这对于使 MoTe2 可用于设备至关重要。该项目嵌入南佛罗里达大学二维材料的研究活动中，将为研究生和本科生提供未来技术相关领域的教育。技术：范德瓦尔斯半导体 MoTe2 具有约 1eV 的相对较小的带隙，是用于双极场效应器件的有前途的材料。在整个可见光谱范围内的强光吸收使得 MoTe2 在光伏领域也很有趣，其带隙值使其成为近红外光电子学的候选者。此外，MoTe2 从半导体到金属的热诱导相变为与范德华半导体进行电接触的材料工程问题提供了可能的解决方案。在这个项目中，我们将通过分子束外延研究和优化 MoTe2 的生长。将研究通过合金化对 MoTe2 进行改性，目的是能够调节带隙和相变行为。这些薄膜的生长及其特性主要通过扫描探针显微镜/光谱学和光电发射来表征，因此我们深入了解了纳米尺度的生长和相变机制。 MoTe2的一个主要缺点是其化学稳定性相对较差，这会导致其在环境条件下降解。为了克服这一稳定性问题，我们将研究氧化物覆盖层对这些 MoTe2 衍生材料的保护。比较了有和没有覆盖层的相变行为，特别是考虑到转变温度对 Te 缺乏的依赖性。最后，制造了 MoTe2 和异种 TMD 之间的面内界面，目的是利用 MoTe2 的相变特性与其他 TMD 半导体形成欧姆接触。因此，该项目将研究 MoTe2 是否可以用作通用材料来解决二维范德华半导体电接触的一般问题。