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

技术摘要该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）掺杂的In 2 O 3稀磁半导体（DMS）中的铁磁性的基本原理。掺杂后的铁磁行为、高居里温度和可控的载流子密度是开发基于自旋的多功能器件的一些关键要求。TM掺杂的In_2 O_3是这样一个独特的系统，对于该系统，控制缺陷浓度可以将电/磁行为从类铁磁金属调谐到铁磁半导体再到顺磁绝缘。通过掺杂、沉积过程中的生长参数和沉积后的退火来控制通过脉冲激光沉积生长的DMS薄膜的载流子密度。原子尺度的结构和界面细节将通过各种最先进的技术，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，透射电子显微镜检查。铁磁性及其与电子特性的相关性将通过磁化和磁输运研究，在高和低磁场和温度低至2 K，使用超导量子干涉装置磁强计和高场磁输运装置。实验数据将测试目前提出的DMS理论模型。从这项研究中产生的自旋物理学的理解将导致新的自旋电子器件的潜在发展，如超灵敏的磁场传感器，基于量子的逻辑和高速计算的存储器。本研究计画将激发及鼓励大学部学生对磁性、半导体物理及自旋电子元件有更深入的了解。非技术性摘要铁磁性的产生是由于相邻电子的磁矩排序，使得它们指向同一方向。许多材料在低温下显示出铁磁性，但只有铁、钴、镍和一些合金在室温以上显示出铁磁性。稀磁半导体（DMS）属于一类新的铁磁体，其通过将稀量的过渡金属（例如铁或钴）并入正常半导体（例如GaAs、ZnO或In 2 O3）中而形成。掺杂后的铁磁特性、高居里温度和可控的电子密度是发展基于自旋的多功能器件的关键要求。这个RUI项目的总体目标是更好地理解铁磁性的基本原理，并控制电子载流子介导的过渡金属（TM）掺杂的In 2 O3稀磁半导体（DMS）中的磁性。 将通过化学掺杂、沉积期间的生长参数和沉积后退火来控制将通过脉冲激光沉积生长的DMS薄膜的电子载流子浓度。结构，磁性和电子特性将通过各种最先进的技术，如X射线衍射，光谱学，原子力显微镜，电子显微镜和超导量子干涉器件磁强计进行研究。实验结果将使用已提出的DMS的理论模型进行分析。这项研究将导致更深入地了解DMS中的铁磁性现象，这将导致新的基于自旋的设备的潜在发展，如超灵敏的磁场传感器，基于量子的逻辑和高速计算的存储器。通过这项研究获得的本科和研究生MS学生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.