The 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.
The 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.
