RUI: N-Type Ferromagnetism in Oxide Based Dilute Magnetic Semiconductors

本RUI项目的总体目标是更好地理解载流子介导的n型过渡金属(TM)掺杂In2O3稀磁半导体(DMS)中铁磁性的基本原理。掺杂后的铁磁行为、高居里温度和可控载流子密度是发展自旋基多功能器件的一些关键要求。Tm掺杂In_2O_3就是这样一种独特的体系，它的缺陷浓度的控制可以调节从铁磁金属到铁磁半导体再到顺磁绝缘的电磁行为。脉冲激光沉积生长的DMS薄膜的载流子密度将通过掺杂、沉积过程中的生长参数和沉积后的退火来控制。原子尺度的结构和界面细节将通过各种最先进的技术来检查，如X射线衍射、拉曼光谱、原子力显微镜、场发射扫描电子显微镜和透射电子显微镜。利用超导量子干涉器件磁强计和高场磁输运装置，在高、低磁场和2K以下的温度下，通过磁化和磁输运研究铁磁性及其与电子性质的关系。实验数据将验证当前提出的DMS理论模型。对自旋物理的理解将导致新的自旋电子器件的潜在发展，如超灵敏磁场传感器、基于量子的逻辑和用于高速计算的存储器。这项研究项目将激励和鼓励本科生对磁学、半导体物理和自旋电子器件有更坚实的理解。非技术性特征铁磁性是由于相邻电子的磁矩有序，使它们指向同一方向而产生的。许多材料在低温下表现出铁磁性，但只有铁、钴、镍和一些合金在室温以上表现出铁磁性，用于有用的应用。稀磁半导体(DMS)是一种新型的铁磁体，它是在常规半导体材料(如GaAs、ZnO或In2O_3)中掺入稀有量的过渡金属如铁或钴而形成的。掺杂后的铁磁性、高居里温度和可控的电子密度是发展自旋基多功能器件的关键要求。RUI项目的总体目标是更好地了解铁磁性的基本原理，并控制电子载体介导的过渡金属(TM)掺杂In2O3稀磁半导体(DMS)中的磁性。脉冲激光沉积DMS薄膜的电子载流子浓度将通过化学掺杂、沉积过程中的生长参数和沉积后的退火热处理来控制。结构、磁性和电子性质将通过各种最先进的技术进行研究，如X射线衍射、光学光谱、原子力显微镜、电子显微镜和超导量子干涉装置磁测量。实验结果将使用已提出的DMS理论模型进行分析。这一研究将加深对DMS中铁磁性现象的理解，从而为超灵敏磁场传感器、量子逻辑和高速计算存储器等基于自旋的新型器件的潜在发展奠定基础。本科生和研究生通过这项研究获得的培训和技能将为他们在高科技行业、学术机构以及政府和私人研究实验室的就业提供良好的服务。

TECHNICAL ABSTRACTThe overall goal of this RUI project is to better understand the fundamentals of ferromagnetism in carrier mediated n-type transition metal (TM)-doped In2O3 dilute magnetic semiconductors (DMS). Ferromagnetic behavior after doping, high Curie temperature, and controllable carrier density are some of the crucial requirements for developing spin-based multifunctional devices. TM-doped In2O3 is such a unique system, for which control of the defect concentration can tune the electrical/magnetic behavior from ferromagnetic metal-like to ferromagnetic semiconducting to paramagnetic insulating. The charge carrier density of thin films of DMS, grown by pulsed laser deposition, will be controlled through doping, growth parameters during deposition, and post-deposition annealing. Structural and interfacial details at atomic scale will be examined by various state-of-the-art techniques such as X-ray diffraction, Raman spectroscopy, atomic force microscopy, field emission scanning electron microscopy, and transmission electron microcopy. Ferromagnetism and its correlations with electronic properties will be investigated through magnetization and magneto-transport studies at high and low magnetic fields and at temperatures down to 2 K using a superconducting quantum interference device magnetometer and a high field magneto-transport set-up. Experimental data will test current theoretical models proposed for DMS. An understanding of spin physics arising from this research will lead to the potential development of new spintronic devices such as ultra-sensitive magnetic field sensors, quantum-based logic, and memory for high speed computation. This research project will motivate and encourage undergraduate students realize a firmer understanding of magnetism, semiconductor physics, and spin-electronic devices.NON-TECHNICAL ABSTRACTFerromagnetism arises due to the ordering of the magnetic moments of neighboring electrons such that they point in the same direction. A number of materials show ferromagnetism at low temperatures, but only iron, cobalt, nickel, and some alloys show ferromagnetism above room temperature for useful applications. Dilute Magnetic Semiconductors (DMS) belong to a new class of ferromagnets, which are formed by incorporating dilute amount of transition metals such as iron or cobalt into normal semiconductors such as GaAs, ZnO, or In2O3. Ferromagnetic behavior after doping, high Curie temperature, and controllable electron density are the crucial requirements for developing spin-based multifunctional devices. The overall goal of this RUI project is to better understand the fundamentals of ferromagnetism and control magnetism in electron carrier mediated transition metal (TM)-doped In2O3 dilute magnetic semiconductors (DMS). The electron carrier concentration of thin films of DMS, to be grown by pulsed laser deposition, will be controlled through chemical doping, growth parameters during deposition, and post-deposition annealing. Structural, magnetic, and electronic properties will be investigated by various state-of-the-art techniques such as X-ray diffraction, optical spectroscopy, atomic force microscopy, electron microcopies, and superconducting quantum interference device magnetometry. Experimental results will be analyzed using the theoretical models which have been proposed for DMS. This research will lead to a deeper understanding of the phenomenon of ferromagnetism in DMS which will lead to the potential development of new spin-based devices such as ultra-sensitive magnetic field sensors, quantum-based logic, and memory for high speed computation. Training and skills acquired by undergraduate and graduate MS students through this research will serve them well for employment in high-tech industry, academic institutions, and government and private research laboratories.