In Situ Characterization of Electrical and Optical Properties of Air-Sensitive Ultra-Thin Films and Thin-Film Interfaces

空气敏感超薄膜和薄膜界面的电学和光学特性的原位表征

• 批准号: 0101856
• 负责人: Arthur Hebard
• 金额: --
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0101856&HistoricalAwards=false
• 关键词: Situ; Characterization; Electrical; Optical; Properties

The focus of this project is on the fabrication and in situ characterization of air sensitive ultra-thin films and thin-film interfaces. The capability to perform these investigations relies on a recently constructed Sample-Handling-In-VAcuum (SHIVA) chamber in which thin-film samples can be reliably connected/disconnected at the deposition station (where optical and transport measurements can be made) and then transferred, without exposure to air, to the bottom of a vacuum-compatible cryostat for low temperature (1.3K) and high field (7T) magnetotransport measurements. The rationale for this approach centers on observations that air sensitivity can be a primary impediment to unraveling intrinsic behavior in a variety of systems. The scope of work will be concentrated in four overlapping areas: percolation and the metal-insulating transition, metal/C60 bilayers and composites, magnetism in reduced dimensions, and the determination of screening lengths at metal-dielectric interfaces. Specific systems to be studied include Ag films near the percolation threshold (exhibits pure geometric behavior and a negative classical magnetoresistance), magnetic (Ni, Fe, Co, Gd) metal/C-60 bilayers and composites (exhibits charge transfer and anomalous positive magnetoresistance), thin disordered magnetic and magnetic semiconductor (e.g., Fe, GdxSi1-x) films, and tunnel junction capacitor structures with magnetic electrodes (exhibits magnetocapacitance due to dependence of screening length on magnetic field). We expect that the SHIVA system will greatly facilitate a comprehensive understanding of novel physical phenomena occurring in air sensitive systems. This research is carried out with students who will acquire training skills that will prepare them for future employment in the scientific/technological sector of our economy. As the thickness of a metallic film decreases, its electrical properties become increasingly sensitive to its interface with the underlying substrate and its interface with the ambient environment. For example, many freshly deposited thin films (e.g., Al, Fe) will rapidly oxidize when exposed to air and, if sufficiently thin, will in a short time become totally oxidized. To measure the intrinsic electrical properties of such air-sensitive thin films, it therefore becomes necessary to utilize specialized techniques in which air is prevented from reaching the sample in the period between its fabrication and electrical characterization. The capability to perform these investigations relies on a recently constructed Sample-Handling-In-VAcuum (SHIVA) chamber in which thin-film samples can be reliably connected/disconnected at the deposition station (where optical and transport measurements can be made) and then transferred, without exposure to air, to the bottom of a separate vacuum-compatible chamber for electrical measurements at low temperatures and high magnetic fields. Specific systems to be studied include metal films near the conduction threshold, magnetic metal/Carbon-60 bilayers and composites, thin disordered magnetic and magnetic semiconductor films, and tunnel junction capacitor structures with magnetic electrodes. We expect that the SHIVA vacuum deposition and characterization system will greatly facilitate a comprehensive understanding of novel physical phenomena occurring in air sensitive systems. Students will participate in this research. They will thereby acquire skills and training in preparation for employment in scientific/technological sectors of industry, academe, and government.

本项目的重点是气敏超薄膜和薄膜界面的制备和原位表征。进行这些调查的能力依赖于最近建造的真空样品搬运试验室，在该试验室中，薄膜样品可以在沉积站可靠地连接/断开(可在其中进行光学和运输测量)，然后在不暴露于空气的情况下转移到与真空兼容的低温恒温器底部进行低温(1.3K)和强场(7T)磁传输测量。这种方法的理论基础是观察到，空气敏感性可能是解开各种系统中固有行为的主要障碍。工作范围将集中在四个重叠领域：渗流和金属绝缘转变，金属/C60双层膜和复合材料，降维磁性，以及金属-电介质界面屏蔽长度的确定。需要研究的具体系统包括接近渗流阈值的Ag薄膜(表现出纯几何行为和负的经典磁阻)，磁性(Ni，Fe，Co，Gd)金属/C-60双层膜和复合材料(表现出电荷转移和反常正磁阻)，薄的无序磁性和磁性半导体(如Fe，GdxSi1-x)薄膜，以及带有磁电极的隧道结电容器结构(由于屏蔽长度随磁场的变化而表现出磁电容)。我们预计，Shiva系统将极大地促进对空气敏感系统中发生的新物理现象的全面了解。这项研究是以学生为对象进行的，他们将获得培训技能，为将来在我国经济的科学/技术部门就业做好准备。随着金属薄膜厚度的减小，其电学性能对其与底层衬底的界面以及与周围环境的界面变得越来越敏感。例如，许多新沉积的薄膜(如Al、Fe)在暴露在空气中时会迅速氧化，如果足够薄，将在很短的时间内完全氧化。因此，为了测量这种气敏薄膜的本征电学性质，有必要利用专门的技术，在制造和电学表征之间的一段时间内防止空气到达样品。进行这些调查的能力取决于最近建造的真空样品搬运处理室，其中薄膜样品可以在沉积站(可以在那里进行光学和运输测量)可靠地连接/断开，然后在不暴露于空气的情况下转移到单独的真空兼容室的底部，以便在低温和高磁场下进行电测量。要研究的具体系统包括接近导通阈值的金属薄膜、磁性金属/碳-60双层膜和复合材料、无序磁性和磁性半导体薄膜，以及带有磁性电极的隧道结电容器结构。我们预计，湿婆真空沉积和表征系统将极大地促进对空气敏感系统中发生的新物理现象的全面了解。学生将参与这项研究。因此，他们将获得技能和培训，为在工业、学术和政府的科学/技术部门就业做准备。