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

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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).