MRI: Acquisition of a Scanning XPS Microprobe

技术摘要凯斯西部储备大学的世伟洛克材料表面分析中心请求美国国家科学基金会资助最先进的XPS系统(X射线光电子能谱，也称为ESCA)。XPS是多用户中心使用最广泛的技术，每年占100多名学术用户使用的仪器的20%。然而，可用的XPS系统是中心所有仪器中最古老的(它有20年的历史了！)并且缺乏重要的能力。我们提出的替代产品PHI 5000 VersaProbe将XPS技术提升到了一个新的水平。它可以将分析的X射线聚焦到直径小于10微米的高强度局部探测器上，并在样品表面上对其进行光栅化。结合表面下XPS探测的浅深度，这将使极少量材料的局部化学分析和高横向分辨率的元素测绘成为可能。该仪器配备了电子能量分析器，针对能量分辨率和高角度接受进行了优化。这将使高性能微区光谱、高灵敏度大面积光谱、二次电子成像和高性能溅射深度剖析成为可能。此外，拟议的仪器还包括一个用于不插手电荷中和的系统，这将极大地方便对非导电样品的分析。中心用户对这些能力的需求很大，这些能力将推动材料研究的许多领域取得重大进展，包括：(I)一种新颖的气相渗碳工艺，通过引入间隙溶质的“巨大”过饱和，使结构合金(如不锈钢)的表面变得超硬，并大大提高耐腐蚀性；(Ii)用于更便宜、更高效的PEM燃料电池的新型催化剂纳米颗粒；(Iii)用于生物医学应用的金刚石电极；以及(Iv)用于神经记录和刺激传感器的基于微制造的灵活电极阵列平台技术。与其广泛的应用范围相对应，新仪器将在凯斯大学研究生和博士后研究人员的教育和培训中发挥重要作用。非技术摘要凯斯西储大学世伟洛克材料表面分析中心要求美国国家科学基金会资助一台最先进的仪器，用于分析不同材料的表面和近表面区域-最上面的2至3层原子-的化学成分。由于表面是材料与其环境相互作用的地方，这种能力对于开发具有优异性能的新材料至关重要。一种成熟且非常有效的表面分析方法是“X射线光电子能谱”：在真空中用软的、低能量的X射线照射材料表面，使表面正下方的前几层原子发出电子(“光电效应”)，通过测量这些带电粒子的能量，可以确定发射它们的原子的化学特性。毫不奇怪，X射线光电子能谱是世伟洛克中心应用最广泛的技术。然而，可用的系统是中心最古老的仪器(它有20年的历史了！)并且缺乏重要的能力。我们提出的替代方案使这项技术更上一层楼。最重要的是，它可以将分析的X射线聚焦到一个小点上，并将其移动到样品表面。结合X射线光电子能谱探测材料的浅层深度，将有可能对非常少量的材料进行局部化学分析，并高精度地绘制整个样品表面的化学成分变化图。此外，通过从一个小的表面区连续去除薄层材料并分析新暴露的材料的表面成分，所提出的仪器可以有效地分析表面下相当深的成分。每年使用世伟洛克中心的100多名材料研究人员中的许多人都非常需要这些能力。新仪器将使材料研究的许多重要领域取得进展，包括：(I)一种使合金(例如不锈钢)表面超硬且更耐腐蚀的新型工艺，通过延长许多技术应用中的金属部件的使用寿命来实现巨大的节能；(Ii)用于更便宜、更高效的便携式燃料电池的新型催化剂纳米颗粒--这种器件将燃料(例如酒精)中所含的化学能直接转化为电能，(Iii)用于不同生物医学应用的新型金刚石电极，以及(Iv)用于连接神经与电子设备的新型微电极阵列。与其广泛的应用范围相对应，新仪器将在CASE研究生和博士后研究人员的教育和培训中发挥重要作用。

Technical AbstractThe Swagelok Center for Surface Analysis of Materials at Case Western Reserve University requests NSF funds for a state-of-the-art XPS system (X-ray photoelectron spectrometry, also known as ESCA). XPS is the most intensively employed technique in the multi-user center, accounting for 20% of instrument use by more than 100 academic users each year. However, the available XPS system is the oldest of all instruments in the center (it is 20 years old!) and lacks important capabilities. The replacement we propose, the PHI 5000 VersaProbe, takes the technique of XPS to the next level. It can focus the analyzing X-rays to a highly intense local probe with a diameter less than 10 um and raster it over the specimen surface. Combined with the shallow depth to which XPS probes below the surface, this will enable local chemical analysis of very small volumes of material and elemental mapping with high lateral resolution. The instrument is equipped with an electron energy analyzer optimized for energy resolution and high-angle acceptance. This will enable high-performance micro-area spectroscopy, high-sensitivity large-area spectroscopy, secondary electron imaging, and high-performance sputter depth profiling. In addition, the proposed instrument includes a system for hands-off charge neutralization, which will greatly facilitate the analysis of non-conducting specimens. These capabilities are much in demand by the center's users and will enable major advances in many areas of materials research, including the development of (i) a novel gas-phase carburization process that makes the surfaces of structural alloys (e.g. stainless steel) ultra-hard and much more corrosion-resistant by introducing a "colossal" supersaturation of interstitial solutes, (ii) novel catalyst nanoparticles for less expensive and more efficient PEM-based fuel cells, (iii) diamond-based electrodes for biomedical applications, and (iv) a micro-fabrication-based, flexible electrode-array platform technology for neural recording and stimulation sensors. Corresponding to its broad range of applications, the new instrument will play an important role in the education and training of graduate students and postdoctoral researchers at Case.Non-Technical AbstractThe Swagelok Center for Surface Analysis of Materials at Case Western Reserve University requests NSF funds for a state-of-the-art instrument for analyzing the chemical composition of the surface and near-surface regions - the topmost 2 to 3 layers of atoms - of diverse materials. Inasmuch as the surface is where materials interact with their environment, this capability is of central importance for developing new materials with superior properties. A well-established and very powerful method for surface analysis is "X-ray photoelectron spectrometry": Irradiating the surface of the material with soft, low-energy X-rays in vacuum causes atoms in the first few layers directly below the surface to give off electrons (the "photoelectric effect"), and by measuring the energy of these charged particles, the chemical identity of the atoms that emitted them can be determined. Not surprisingly, X-ray photoelectron spectrometry is the most intensively employed technique in the Swagelok Center. However, the available system is the oldest instrument in the center (it is 20 years old!) and lacks important capabilities. The replacement we propose takes the technique to the next level. Most importantly, it can focus the analyzing X-rays to a small spot and move it across the specimen surface. Combined with the shallow depth to which X-ray photoelectron spectrometry probes the material, local chemical analysis of very small volumes of material will be possible, as well as mapping variations in chemical composition across the specimen surface with high accuracy. Moreover, the proposed instrument can efficiently analyze the composition at considerable depths below the surface by successively removing thin layers of material from a small surface region and analyzing the surface composition of the freshly exposed material. These abilities are much in demand by many of the more than 100 materials researchers using the Swagelok Center each year. The new instrument will enable progress in many important areas of materials research, including the development of (i) a novel process that makes the surface of alloys (e.g. stainless steel) ultra-hard and much more corrosion-resistant, providing tremendous energy-savings by extending the lifetime of metal parts in many technical applications, (ii) novel catalyst nanoparticles for less expensive and more efficient portable fuel cells - devices that convert the chemical energy contained in a fuel (e.g. alcohol) directly to electricity, (iii) novel diamond electrodes for diverse biomedical applications, and (iv) novel microelectrode arrays for contacting nerves to electronic devices. Corresponding to its broad range of applications, the new instrument will play an important role in the education and training of graduate students and postdoctoral researchers at Case.