Magnetic Moments in Amorphous Semiconductors

非晶半导体中的磁矩

• 批准号: 0505524
• 负责人: Frances Hellman
• 金额: --
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2010-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0505524&HistoricalAwards=false
• 关键词: Magnetic; Moments; Amorphous; Semiconductors

TECHNICAL EXPLANATION This project will investigate the effect of adding magnetic moments to semiconductors on the electrical and magnetic properties of the resultant materials. The focus will be on amorphous semiconductors where a wide variety of dopants can be readily introduced without damaging the structure. Amorphous Si, Ge, and various forms of C doped with magnetic ions such as rare earth elements, Fe and Mn will be prepared and their electronic, magnetic, thermodynamic, and structural properties measured. The influence of the phonon stiffness and the semiconductor band gap on these properties will be determined. In amorphous C, the bonding can and will be varied from graphitic to diamond-like, allowing the band gap to be tuned from near zero to large. The interaction between the added local moments and the spontaneous moments formed at the Metal-Insulator transition as electrons localize will be studied. The research will provide a phenomenological underpinning for a microscopic model for the three dimensional Metal-Insulator transition, and an understanding of the effect on both transport and magnetic properties of introducing local magnetic moments into a semiconductor. The project will provide research training and education for two graduate students and an estimated 5-6 undergraduates, including exposure to industry and to the national laboratories through the PI's collaborations with the magnetic recording industry and with the National High Magnetic Field Lab and Lawrence Berkeley Lab. NON-TECHNICAL EXPLANATIONThe deliberate addition of magnetism or "magnetic moments" to semiconductors produces effects that are extremely large. In particular the change in the electrical resistance when such a material is placed in a magnetic field (magnetoresistance) can be enormous. This project will investigate the effect of adding magnetic atoms to amorphous (non-crystalline) semiconductors Si, Ge, and C, deliberately creating and studying new materials not previously made. Films of amorphous Si, Ge, and C doped with magnetic ions such as rare earth elements, Fe, and Mn will be prepared. Their electronic, magnetic, thermodynamic, and structural properties will be measured over a wide range of temperature, magnetic field, and doping levels. The research will attempt to determine the principles governing the large effect of magnetic moments in semiconductors. An increased understanding of these effects may point the way to making the very large magnetoresistance of use to a developing technology that will use the magnetic property of the electron, its "spin" in addition to its charge, i.e. spin electronics. In addition this research aims to increase our understanding of why magnetic moments play such a crucial role in materials of current interest, such as the high temperature superconductors. The project will provide research training and education for graduate and undergraduate students, and provide them with an exposure to industry and to the national labs through collaborations. Thus, the students will be well prepared for future careers in academia, or industrial or government laboratories.

技术说明 该项目将研究向半导体添加磁矩对所得材料的电学和磁学性质的影响。重点将放在非晶半导体上，其中可以很容易地引入各种掺杂剂而不损坏结构。将制备掺杂有稀土元素、Fe 和 Mn 等磁性离子的非晶 Si、Ge 和各种形式的 C，并测量它们的电子、磁、热力学和结构性能。将确定声子刚度和半导体带隙对这些特性的影响。在无定形碳中，键合可以并且将会从石墨态变为类金刚石态，从而允许带隙从接近零调整到大。将研究电子局域化时添加的局部力矩与金属-绝缘体转变时形成的自发力矩之间的相互作用。该研究将为三维金属-绝缘体转变的微观模型提供现象学基础，并了解将局部磁矩引入半导体对输运和磁性能的影响。该项目将为两名研究生和大约 5-6 名本科生提供研究培训和教育，包括通过 PI 与磁记录行业以及国家高磁场实验室和劳伦斯伯克利实验室的合作，接触行业和国家实验室。非技术解释故意向半导体添加磁性或“磁矩”会产生非常大的效应。特别是，当这种材料被置于磁场中时，电阻的变化（磁阻）可能是巨大的。该项目将研究向非晶态（非晶态）半导体 Si、Ge 和 C 添加磁性原子的效果，有意创造和研究以前未制造过的新材料。将制备掺杂稀土元素、Fe、Mn 等磁性离子的非晶 Si、Ge 和 C 薄膜。它们的电子、磁性、热力学和结构特性将在很宽的温度、磁场和掺杂水平范围内进行测量。该研究将尝试确定控制半导体中磁矩巨大影响的原理。对这些效应的进一步了解可能会为开发技术指明道路，该技术将利用电子的磁性、电子的“自旋”以及电荷，即自旋电子学。此外，这项研究旨在加深我们对为什么磁矩在当前感兴趣的材料（例如高温超导体）中发挥如此重要作用的理解。该项目将为研究生和本科生提供研究培训和教育，并通过合作为他们提供接触行业和国家实验室的机会。因此，学生将为未来在学术界、工业或政府实验室的职业生涯做好充分准备。