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.

技术解释该项目将研究将磁矩添加到半导体对所得材料电气和磁性特性的影响。重点将放在无定形的半导体上，可以轻松地引入各种掺杂剂而不会损害结构。将制备具有磁性离子（例如稀土元件，Fe和Mn）的各种形式的无定形Si，GE和各种形式的C，并测量其电子，磁性，热力学和结构特性。将确定声子刚度和半导体带隙对这些性质的影响。在无定形的C中，键合的键可以并且将从类似钻石变化，从而使带隙从零接近到大。将研究随着电子本地化而在金属 - 绝缘体过渡处形成的自发力矩之间的相互作用。这项研究将为三维金属 - 绝缘体跃迁的微观模型提供一个现象学的基础，并了解将局部磁矩引入半导体的运输和磁性的影响。该项目将通过PI与磁性记录行业的合作以及国家高磁场实验室和劳伦斯·伯克利伯克利实验室的合作，为两名研究生和估计的5-6名本科生提供研究培训和教育，包括接触工业和国家实验室。非技术解释是故意向半导体添加磁性或“磁矩”会产生极大的效果。特别地，当将这种材料放置在磁场（磁场抗性）中时，电阻的变化可能是巨大的。该项目将研究将磁原子添加到无定形（非晶体）半导体SI，GE和C的效果，故意创建和研究以前未制造的新材料。将制备用磁离子，例如稀土元件，Fe和Mn等磁离子掺杂的无定形Si，GE和C的膜。它们的电子，磁性，热力学和结构特性将在广泛的温度，磁场和掺杂水平上进行测量。该研究将试图确定管理半导体磁矩的巨大影响的原理。对这些效果的越来越多的理解可能指向开发技术的使用非常大的磁场，该技术将使用电子的磁性，除了电荷（即自旋电子设备）之外，其“自旋”。此外，这项研究旨在提高我们对磁矩为何在当前感兴趣的材料（例如高温超导体）中发挥如此关键作用的理解。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行业和国家实验室的接触。因此，学生将为学术界或工业或政府实验室的未来职业做好充分的准备。