Development of a Nondestructive Microprobe for Research and Education on Multiscale Materials Physics

来自主要仪器计划的这一奖项为加州大学滨江的科学家提供了支持，他们正在开发一种微探针，可以拍摄照片，揭示物体中可能存在的各种原子级缺陷的空间分布。固体中的纳米级缺陷可以相互作用，产生宏观效应，以响应所施加的应力，例如老化、风化和开裂。了解孤立缺陷转化为重大缺陷的机制对于预测和最终防止许多对社会至关重要的材料失效至关重要。 将宏观事件与其前兆相关联的一个基本要素是图像的可用性，这些图像可以显示原子缺陷在许多长度尺度上的空间分布和组织。正电子微探针具有无与伦比的灵敏度，可检测许多材料中百万分之一浓度水平的开放体积缺陷。我们的目标是开发一种仪器，包括一个扫描正电子微探针，可以捕获图像的材料缺陷，具有高的数据速率和分辨率，使厘米尺寸的样品可以被视为微米分辨率。微探针将在许多科学学科中发挥作用，导致包括环境科学和地质学在内的不同领域的进步，其中岩石的检查可以揭示污染物运输的途径，并阐明最早生命形式的重要证据。微探针仪器将结合联合收割机：（a）用于晶体缺陷和孔隙度的正电子微探针;（B）用于引入热梯度和声冲击并用于测量表面反射率的皮秒激光探针;（c）用于在不干扰样品的情况下精确测量感兴趣区域的20 nm分辨率特征的扫描电子微探针;以及（d）样品制备和表面光谱站。扫描正电子微探针将具有比任何现有正电子探针大两个数量级的数据收集速率，并且将首次允许在有用的实验室时间尺度内在宏观上感兴趣的距离上以1微米分辨率获得图像，即，几个小时.这种独特的正电子探针与两种成熟的工具相结合，即，SEM和光学成像将使结构研究的空间尺度从原子缺陷延伸到宏观断裂的毫米尺度和时间研究从皮秒到天。 将所有仪器组合在同一样品室中的目的是确保原子级缺陷不会因样品的重新安装和处理而改变，并且样品上的应力对于所有3个表征保持相同。 因此，该仪器将具备SEM/激光/光学的所有优点，并结合与原子级缺陷相关的独特正电子对比度图像。几名学生将接受有关该仪器原理、结构和操作细节的培训。微探针的可用性将是形成一个跨部门研究小组的基础，该小组专注于了解由应力或能量梯度驱动的系统在许多长度尺度上组织的众所周知的趋势。将开发一种结合正电子、电子和激光微探针的新型显微镜，使科学家能够研究原子级缺陷如何影响固体材料的物理性质，以及相邻的原子级缺陷如何逐渐组织成更大的缺陷，如裂纹。 该仪器的核心是一个正电子微探针，它具有无与伦比的灵敏度，可以检测到少数原子从其通常位置丢失的缺陷。 通过将正电子微探针与可以解析数百个原子尺度的结构的传统电子显微镜和可以解析微米尺度结构的脉冲激光显微镜相结合，将有可能直接解析单个原子缺陷如何演变成越来越大的结构。 有了这种仪器的新认识，材料科学家有一天可能能够预测裂缝将在应变，老化或风化的物体中形成。 这将允许测试和设计用于半导体设备，飞机涡轮机和核废料储存容器的更坚固耐用的材料。 新的微探针将是有用的，在所有的科学学科，固体材料的性质是重要的。 例如，它可能导致环境科学和地质学的进步，对岩石的检查可以揭示污染物移动的路径，并为最早的生命形式提供证据。几名学生将接受有关拟议仪器的原理、结构和操作细节的培训。 一旦可用，微探针将成为一个跨部门研究小组的基础，该小组的研究重点是了解所有复杂系统在受到压力时在许多长度尺度上做出反应的一般趋势。 最终目标是找到新的物理原理，使我们能够预测各种各样看似无关的复杂系统的行为，从固体中的原子系统到星系中的天体系统，细胞中的分子或殖民地中的有机体。

This award from the Major Instrumentation Program provides support to scientists at the University of California, Riverside who are developing a microprobe that can take pictures revealing the spatial distributions of various atomic-scale defects that may be present in an object. Nanoscale imperfections in solids can interact to produce macroscopic effects in response to applied stress, such as aging, weathering and cracking. Understanding the mechanisms for the transformation of isolated defects into significant imperfections is crucial to predicting and ultimately preventing failure in many materials of key importance to society. An essential element to correlating macroscopic events with their precursors would be the availability of images that could show the spatial distribution and organization of atomic defects on many length scales. The positron microprobe has an unrivaled sensitivity for detecting open volume defects at the parts-per-million level of concentration in many materials. The objective is to develop an instrument that includes a scanning positron microprobe that can capture images of material defects with a high data rate and resolution such that centimeter size samples can be viewed with micron resolution. The microprobe will be useful across many scientific disciplines, leading to advances in diverse fields including environmental science and geology where the examination of rocks could reveal pathways for the transport of pollutants and elucidate important evidence for the earliest life forms. The microprobe instrument will combine (a) a positron microprobe for crystalline imperfections and porosity; (b) a picosecond laser probe for introducing thermal gradients and acoustic shocks and for measuring surface reflectivity; (c) a scanning electron microprobe for measuring features at 20 nm resolution on precisely the area of interest without disturbing a sample; and (d) a sample preparation and surface spectroscopy station. The scanning positron microprobe will have a two orders of magnitude greater data collection rate than any existing positron probe and would for the first time allow obtaining images at 1 micron resolution over macroscopically interesting distances in useful laboratory timescales, ie., several hours. The combination of this unique positron probe with two well-established tools, ie., SEM and optical imaging, would enable structure studies on spatial scales extending from atomic defects to macroscopic fracture on the mm scale and temporal studies from picoseconds to days. The object of having all instruments combined in the same sample chamber is to ensure that the atomic scale defects are not changed by remounting and handling of the sample and that the stresses on the sample remain the same for all 3 characterizations. The proposed instrument will thus have all the advantages of SEM/laser/optics combined with a unique positron contrast image linked to atomic-scale defects.Several students will be trained in the details of the principles, construction and operation of the proposed instrument. The availability of the microprobe will be the basis for the formation of an interdepartmental group of researchers focused on understanding the well known tendency of systems driven by stress or energy gradients to organize at many length scales. A new type of microscope combining positron, electron, and laser microprobes will be developed that will allow scientists to study how atomic-scale defects affect the physical properties of solid materials and how neighboring atomic-scale defects are gradually organized into much larger imperfections such as cracks. The core of the instrument is a positron microprobe, which has an unrivaled sensitivity for detecting defects in which a handful of atoms are missing from their usual location. By combining the positron microprobe with a conventional electron microscope that can resolve structures on the scale of 100's of atoms and a pulsed laser microscope that can resolve structure on a micron scale, it will be possible to directly resolve how individual atomic defects evolve into larger and larger structures. With the new understanding made possible by such an instrument, materials scientists may one day be able to predict where cracks will form in a strained, aging, or weathered object. This will allow to test and design stronger and more durable materials for semiconductor devices, airplane turbines, and nuclear waste storage containers. The new microprobe will be useful in all scientific disciplines where solid material properties are important. For example, it may lead to advances in environmental science and geology where the examination of rocks could reveal pathways for pollutants to move and provide evidence for the earliest forms of life. several students will be trained in the details of the principles, construction, and operation of the proposed instrument. Once available, the microprobe will be the basis for the formation of an interdepartmental group of researchers focused on understanding the general tendency of all complex systems to respond on many length scales when they are strained. The ultimate goal would be to find new physical principles which would allow us to predict the behavior of a wide variety of seemingly unrelated complex systems ranging from systems of atoms in a solid to systems of astronomical bodies in a galaxy, molecules in a cell, or organisms in a colony.