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X-Ray Photoelectron and Auger Electron Spectroscopy
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
C. R. Brundle, J. F. Watts, J. Wolstenholme
UHV conditions are usually obtained in a modern electron spectrometer by use of ion pumps or turbomolecular pumps. Diffusion pumps, which were popular some time ago (Brundle et al., 1974), have now largely disappeared from modern commercial instruments. Whichever type of pump is chosen, it is common to use a titanium sublimation pump to assist the prime pumping and to achieve the desired vacuum level. All UHV systems need baking from time to time to remove adsorbed layers from the chamber walls.
System Design
Published in Pramod K. Naik, Vacuum, 2018
For applications requiring a clean organic contamination-free vacuum, it is necessary to employ a cryo-pumped system or an ion pumped system. As in the case of most high vacuum pumps, forepressure needs to be provided by a mechanical pump before the cryopump is started. The mechanical pump can also be used during the regeneration of the cryo-pump while the condensed gas is exhausted by heating. For applications that demand a clean organic contaminationfree vacuum, it is necessary to employ a cryo-sorption pumped system. Systems using combinations of sputter-ion pumps, getter-ion pumps, titanium sublimation pumps non-evaporable getter pumps, turbo molecular pumps, cryo-sorption pumpd are most commonly used for experimental work in UHV range, surface analytical equipment and particle accelerators.
Organic/Metal Interface Properties
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
For nitrogen, if T = 300 K and P = 10−6 Torr, then ρ × 5 = 1014/cm2 s. If every atom that strikes the surface sticks, then a monolayer of nitrogen will grow in 2 s. Since surface contamination may result in interactions between the adsorbate and the substrate, it is necessary to minimize exposure of the sample to contaminants. Consequently, detailed surface studies require a highly controlled environment with a pressure about 10−10 Torr. This range of pressure is usually referred to as ultrahigh vacuum (UHV).
Charge transfer of keV-energy H+ ions in grazing scattering on Cu(100)
Published in Radiation Effects and Defects in Solids, 2023
Wenhao Liang, Yanghui Weng, Yue Guo, Guang Zhong, Lei Wan, Hong Lin, Bin Ding, Luyao Zhang, Jiawei Wang, Yanling Guo, Lin Chen, Ximeng Chen, Zhen Yang
The experiment is performed in the Particle Beam Application Laboratory, located at School of Nuclear Science and Technology, Lanzhou University. The schematic diagram of the setup is shown in Figure 1. The H+ ions with incident energies from 0.5 keV to 5.0 keV are produced in a homemade electron-impact ion source and selected by a homemade velocity selector from H+, H2+ and H3+ particles, and then collimated by several slits, focused by electrostatic lens and directed to Cu(100) located at the center of the main ultrahigh-vacuum (UHV) chamber. Three-stage differential pumping mode has been adopted by using several holes fixed in the beam line. The vacuum in the part near the ion source is about 3 × 10-3 Pa, pumped by a turbo molecular pumper with the speed of 300 L/s. The beam line is pumped by a small turbo molecular pumper with the speed of 100 L/s. The main UHV chamber is pumped by a turbo molecular pumper with the speed of 980 L/s in series with another one with 600 L/s. The size of the beam spot is 1 × 3 mm2. The scattering angle is 7° and the incident angle measured with respect to the surface plane is changed by rotating the sample holder of the manipulator. The details of the description of the experimental setup can be found elsewhere (56–58).
Application of work function measurements in the study of surface catalyzed reactions on Rh(1 0 0)
Published in Catalysis, Structure & Reactivity, 2018
Basar Caglar, Ali Can Kizilkaya, J. W. (Hans) Niemantsverdriet, C. J. (Kees-Jan) Weststrate
The experiments were performed in a home-built UHV chamber with a base pressure ≤ 3 × 10−10 mbar. Pressures in both chambers were measured using a cold cathode gauge (ActiveLine PKR251). A typical cleaning cycle consists of sputter-annealing cycles followed by oxygen treatment to remove surface carbon, described in detail elsewhere [10]. A UHV Kelvin probe (UHV KP 4.5, KP Technology) was used to measure ∆Φ. It consists of a stainless steel disc which is suspended parallel to the Rh(1 0 0) crystal to form a simple capacitor (Figure 1(b)). The oxide layer on the stainless steel tip makes it comparatively inert for adsorption of reactants such as CO. For example, CO desorption from chromium oxide, one of the oxides expected to be present at a stainless steel surface, occurs around 180 K already [11]. As the tip is kept at room temperature throughout the experiments CO adsorption on the tip is negligible. In general, no indications were found throughout the experiments presented here as well as elsewhere [2–5] that the work function measurement was affected by a change of the work function of the tip.