Refurbishment of a materials growth system for research into novel quantum materials

本研究工具和仪器（RTI）拨款提案的目的是获得购买，转换和升级分子束外延（MBE）系统所需的资金，用于合成新型金属硫系量子材料。这些量子材料的独特和令人兴奋的特性是电子在其表面自由流动而不损失能量，而晶体的大部分仍然是绝缘体。在过去的几个月里，理论学家预测，几种铋和锑化合物的行为类似于所谓的拓扑绝缘体。2009年6月发表的关于碲化铋块状晶体的第一批结果证实了理论预测。现在，能够快速生长具有极高晶体质量的外延薄膜材料非常重要，以便详细研究拓扑绝缘体的性质并使其能够应用。尤其令人兴奋的是，研究图像磁单极子的前景，以及开发速度更快、几乎没有功率、效率更高的计算机芯片的前景。MBE是合成定制高质量异质结构的首选方法，这些异质结构在室温下显示出所需的性能。我们感兴趣的主要物质系是十四烯矿族。突出的例子是硒化铋（Bi2Se3）和碲化铋（Bi2Te3），它们是V/VI族窄带隙半导体。Bi2Se3和Bi2Te3除了适用于光器件外，还可用作室温热电材料。待转换的MBE系统用于固体物理研究。该系统处于良好的状态（生长室达到1*10^{-11}Torr的基压），并且可以很容易地以最小的成本适应所提出的V/VI工作。该系统配备了砷和锑源，这也是拟议研究（GaAs缓冲层，as覆盖层和sb基化合物）所需要的。要求的关键部件包括硒和碲裂解单元、控制软件升级、氢清洁源以及分析工具（RHEED、x射线探测器、视线质谱仪）。

The purpose of this Research Tools and Instruments (RTI) Grant proposal is to obtain funding required to purchase, convert and upgrade a molecular beam epitaxy (MBE) system for the synthesis of novel metal chalcogenide quantum materials. The unique and exciting property of these quantum materials is the free flow of electrons across their surfaces with no loss of energy - while the bulk of the crystal remains an insulator. In the past months, theorists have predicted that several bismuth and antimony compounds behave like so-called topological insulators. First results, published in June of 2009 on bismuth telluride bulk crystals confirmed the theoretical predictions. It is now of great importance to be able to quickly grow epitaxial thin film materials with extremely high crystal quality in order to both study the properties of topological insulators in great detail and to enable applications. Particularly exciting is the prospect of being able to study an image magnetic monopole and to develop dramatically faster, almost powerless, and more efficient computer chips. MBE is the method of choice for the synthesis of tailored high-quality heterostructures that show the desired properties at room-temperature. The prime materials system of interest is the tetradymite group. Prominent examples are bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3), which are group V/VI narrow bandgap semiconductors. Apart from being suitable for optical devices, Bi2Se3 and Bi2Te3 are used as room-temperature thermoelectric materials. The MBE system to be converted was used for solid state physics research. This system is in excellent condition (the growth chamber reaches a base pressure of 1*10^{-11} Torr) and it can be easily adapted for the proposed V/VI work at minimal cost. The system is outfitted with arsenic and antimony sources, which are also needed for the proposed research (for GaAs buffer layers, As-capping and Sb-based compounds). Critical parts requested include cracker cells for selenium and tellurium, a control software upgrade, a hydrogen cleaning source, as well as analytical tools (RHEED, X-ray detector, line-of-sight mass spectrometer).