Spectroscopy low energy electron diffraction

Auger electron spectroscopy. X-ray photoelectron spectroscopy, low-energy electron diffraction, and in situ STM have been employed to investigate two-step alternate electrodeposition of Cd and Te atomic layers, forming finally, CdTe monolayers (electrochemical ALE on Au(lll)) [451]. STM images suggest that previously proposed hexagonal structures for CdTe may not be correct. 

Ueb] Auger electron spectroscopy, low energy electron diffraction 15 mass% Cr, < 0.03 mass% N, surface segregation of nitrides... 

LEIS LEED LEPD Low-Energy Ion Spectroscopy Low-Energy Electron Diffraction Low-Energy Positron Diffraction ... 

Several experimental techniques can be used to study surfaces. X-ray Photoelectron Spectroscopy (XPS), Auger Spectroscopy, X-ray Absorption Spectroscopy, Low Energy Electron Diffraction (LEED), Infra-Red spectroscopy (IR), Raman spectroscopy. Time of Flight Secondary Ionization Mass Spectroscopy (ToF-SIMS), different microscopy techniques, cyclic voltammetry and many other methods have been used to understand the chemical composition and also the reactivity of many sulfide surfaces. However, any analysis using these methodologies are not limited to surface atoms and contributions from the bulk phase are also included. In LEED, for example, in which the incident electrons are elastically backscattered from a surface and subjected to diffraction, the electrons can travel around 5-20 A into the solid. This will make any spectra analysis very difficult and, sometimes, not conclusive. 

HEED = high energy electron diffraction IILE = ion-induced light emission INS = ion-neutralization spectroscopy IRS = infrared spectroscopy ISS = ion-scattering spectroscopy LEED = low energy electron diffraction LEIS = low energy ion scattering ... 

The most appropriate experimental procedure is to treat the metal in UHV, controlling the state of the surface with spectroscopic techniques (low-energy electron diffraction, LEED atomic emission spectroscopy, AES), followed by rapid and protected transfer into the electrochemical cell. This assemblage is definitely appropriate for comparing UHV and electrochemical experiments. However, the effect of the contact with the solution must always be checked, possibly with a backward transfer. These aspects are discussed in further detail for specific metals later on. 

Michaelis R, Zei MS, Zhai RS, Kolb DM (1992) The effect of halides on the structure of copper underpotential-deposited onto Pt(lll) a low-energy electron diffraction and X-ray photoelectron spectroscopy study. J Electroanal Chem 339 299-310... 

The apparatuses used for the studies of both ammonia synthesis emd hydrodesulfurization were almost identical, consisting of a UHV chamber pumped by both ion and oil diffusion pumps to base pressures of 1 x10 " Torr. Each chamber was equipped with Low Energy Electron Diffraction optics used to determine the orientation of the surfaces and to ascertain that the surfaces were indeed well-ordered. The LEED optics doubled as retarding field analyzers used for Auger Electron Spectroscopy. In addition, each chamber was equipped with a UTI 100C quadrupole mass spectrometer used for analysis of background gases and for Thermal Desorption Spectroscopy studies. 

As mentioned previously, this can be attributed in part to the lack of structure-sensitive techniques that can operate in the presence of a condensed phase. Ultrahigh-vacuum (UHV) surface spectroscopic techniques such as low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and others have been applied to the study of electrochemical interfaces, and a wealth of information has emerged from these ex situ studies on well-defined electrode surfaces.15"17 However, the fact that these techniques require the use of UHV precludes their use for in situ studies of the electrode/solution interface. In addition, transfer of the electrode from the electrolytic medium into UHV introduces the very serious question of whether the nature of the surface examined ex situ has the same structure as the surface in contact with the electrolyte and under potential control. Furthermore, any information on the solution side of the interface is, of necessity, lost. 

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