Doping Dependent Transition from Paramagnetism to Ferromagnetism in Semiconductors

技术革命已经使高速计算和信息存储在地球上几乎任何地方触手可及，为了加速技术革命，新的想法是必不可少的。半导体器件设计的一个进步途径，被称为自旋电子学，寻求利用磁性自由度达到与目前硅技术中使用的电荷自由度相同的程度。当科学家们试图控制或操纵电子自旋（电子固有的磁性）时，他们已经认识到磁性和半导体材料的实用性。然而，在目前已知的少数此类系统中，没有一个完全满足诸如与硅的兼容性，室温磁性以及与自旋电子学技术所需的电信号和光信号耦合的可能性等要求。正如许多新兴技术一样，对材料和物理特性的基本探索可以带来突破。该项目研究了一系列磁性和半导体材料，以探索磁性的机制，包括电子和磁性自由度的相互作用，并记录这些相互作用对这些系统物理性质的影响。不同层次的学生，以及高中教师，将探索这些磁性半导体晶体、薄膜和纳米线形式的磁性、电学、光学和热力学性质。虽然磁性半导体由于其在自旋电子学器件中的潜在用途而受到了极大的关注，但从基本观点来看，它们仍然缺乏探索。特别是，将通常压倒性的缺陷相关问题与更有趣的基本行为分开是非常困难的。该项目将研究一组磁性和半导体硅化物和硫化物，其中仔细的表征表明，二次相和缺陷相关的问题是不相关的。这种对材料特性的控制使我们能够进入一种独特的状态，即通过晶体、薄膜和纳米线中的化学取代，接近半导体中顺磁性绝缘体向磁性金属的过渡。不同层次的学生和高中教师将会探索这些材料，寻找新的传输、磁性、热力学和光学性质，这些性质可能会在未来的技术中得到利用。

Non-technical abstractIn order to accelerate the technological revolution that has placed high speed computation and information storage at our fingertips almost anywhere on Earth, new ideas are essential. One pathway for progress in semiconductor device design, known as spintronics, seeks to make use of the magnetic degrees of freedom to the same extent that charge degrees of freedom are used in present day silicon technologies. As scientists have sought to control or manipulate the electron spin, the intrinsic magnetic property of electrons, they have recognized the utility of materials that are both magnetic and semiconducting. However, of the small number of such systems presently known, none completely meet requirements such as compatibility with silicon, room temperature magnetism, and the possibility of coupling to electrical and optical signals that are necessary for spintronics technologies. As is true of many nascent technologies, fundamental explorations of material and physical properties can lead to breakthroughs. This project investigates a range of magnetic and semiconducting materials to explore the mechanisms for magnetism which includes the interaction of electronic and magnetic degrees of freedom and to document the ramifications of these interactions on the physical properties of these systems. Students on many levels, as well as high school teachers, will be exploring magnetic, electric, optical, and thermodynamic properties of these magnetic semiconductors in crystalline, thin film, and nanowire form. Technical abstractAlthough magnetic semiconductors have received enormous attention because of their potential use in spintronics devices, from a fundamental viewpoint they remain poorly explored. In particular, it has been very difficult to separate the often overwhelming defect related issues from the more interesting essential behaviors. This project will investigate a set of magnetic and semiconducting silicides and sulfides where careful characterization has demonstrated that secondary phases and defect related issues are not relevant. This control over materials properties allows access to a unique regime, that near the transition(s) from paramagnetic insulator to magnetic metal in a semiconductor by way of chemical substitution in crystals, thin films, and nanowires. Students on many levels, as well as high school teachers will be exploring these materials searching for novel transport, magnetic, thermodynamic, and optical properties that may, perhaps, be exploited in future technologies.