Development of a Dynamic Helium Atom Scattering Apparatus to Probe Nanoscale Surface Fluctuations

开发动态氦原子散射装置来探测纳米级表面涨落

• 批准号: 0079584
• 负责人: Stephen Kevan
• 金额: $ 30.45万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-08-15 至 2004-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0079584&HistoricalAwards=false
• 关键词: Development; Dynamic; Helium; Atom; Scattering

Most areas of modern materials research focus fundamentally on energetic interactions that operate on the nanometer length scale but which nonetheless are manifested in unusual macroscopic material properties. While many techniques are available to probe the static microscopic properties of materials, few provide microscopic information on the moderate time scales (1 ms - 1 s) characteristic of dynamical modes that determine the interplay between microscopic and macroscopic worlds. There is therefore an urgent need to develop new techniques that combine high spatial and temporal resolution. Professor Kevan and his co-investigators will construct novel apparatus to produce a transversely coherent helium atom beam. They will develop methodologies analogous to dynamic laser light scattering and apply these to study surface fluctuations at length scales as short as a few nanometers and on time scales as short as one microsecond. Examples of phenomena to be studied using this new technique include 1) the elementary steps in diffusion of surface species, 2) equilibrium and steady-state surface fluctuations in conducting and non-conducting polymer and self-assembled monolayer films, and 3) the fluctuations of high temperature superconductors in the spin-charge segregated phase. The PI is developing a helium atom scattering apparatus, to probe nanoscale surface fluctuations. A key focus of modern materials research is to control a material's structure in order to understand and ultimately control its function. Understanding structure requires measuring how atoms are arranged in space and how they are bonded to each other to form molecules and solids. This pertains to a material's static properties. By contrast, understanding function requires measuring how a material operates, either mechanically, chemically, electrically, or magnetically. Function is intrinsically a dynamical concept. While there are many structural techniques - various microscopes and x-ray diffraction, for example - there are only relatively few that provide incisive information about a material's dynamical properties on a length scale ranging from a few to many atoms. That many key technologies rely on materials that are artificially patterned on this scale makes it urgent to develop such techniques. Here the investigators are developing a novel use for helium atoms to try to address this need. Like x-rays, helium atoms can probe very short dimensions. The instrument will produce a very highly collimated beam of atoms that will have some laser-like properties. This will allow application of laser-like dynamical techniques, but with sensitivity to sizes on the scale of atoms.

现代材料研究的大多数领域基本上集中在纳米尺度上运行的能量相互作用，但这些相互作用仍然表现为不寻常的宏观材料性质。虽然有很多技术可以用来探测材料的静态微观性质，但很少有技术提供关于动态模式的中等时间尺度(1ms-1 S)的微观信息，这些模式决定了微观和宏观世界之间的相互作用。因此，迫切需要开发结合高空间和时间分辨率的新技术。凯文教授和他的合作研究人员将建造新的设备来产生横向相干的氦原子束。他们将开发类似于动态激光光散射的方法，并将这些方法应用于研究短至几纳米的长度尺度上的表面波动和短至一微秒的时间尺度上的表面波动。用这种新技术研究的现象包括1)表面物种扩散的基本步骤，2)导电和非导电聚合物和自组装单层膜中的平衡和稳态表面涨落，以及3)高温超导体在自旋-电荷分离相中的涨落。PI正在开发一种氦原子散射仪，以探测纳米尺度的表面波动。现代材料研究的一个关键焦点是控制材料的结构，以便理解并最终控制其功能。理解结构需要测量原子在空间中是如何排列的，以及它们是如何相互结合形成分子和固体的。这与材质的静态属性有关。相比之下，理解功能需要测量一种材料是如何工作的，无论是机械的、化学的、电气的还是磁性的。函数本质上是一个动力学概念。虽然有许多结构技术--例如各种显微镜和x射线衍射--但在从几个原子到许多个原子的长度范围内，提供关于材料动力学性质的精辟信息的技术相对较少。许多关键技术依赖于在这种规模上人工制作图案的材料，这使得开发这种技术变得迫切。在这里，研究人员正在开发氦原子的一种新用途，试图满足这一需求。像x射线一样，氦原子可以探测非常短的维度。该仪器将产生高度准直的原子束，它将具有一些激光性质。这将允许应用类似激光的动力学技术，但对原子尺度上的大小敏感。