UV Photoelectron Spectroscopy UPS

The nature of the final state depends upon the energy, hv, of the exciting photons. In X-ray photoelectron spectroscopy (XPS) the exciting photons are provided by sources such as A1 Ka (1,486 eV) or Mg Ka (1,253 eV) and excitation of the core electrons of the molecules is observed. In UV photoelectron spectroscopy (UPS), Hel (21.2eV) or Hell (40.8 eV) radiation is used and excitation from the valence region of the neutral molecule is observed. XPS and UPS are surface-sensitive techniques, which are capable of providing extremely useful information on the chemical nature of a surface or interface and, in the case of the XPS, the conformational state of the molecules at the surface [64]. 

UV-photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) are powerful analytical tools the energy of the photons required to eject the electron is characteristic of an element and of its oxidation state. 

The experiments were performed in stainless steel UHV chambers which were equipped with the instrumentation necessary to perform Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), UV Photoelectron Spectroscopy (UPS), Low Energy Electron Diffraction (LEED), work function measurements (A( )), High Resolution Electron Energy Loss Spectroscopy (HREELS), and Temperature Programmed Desorption (TPD). The Au(lll) crystal was heated resist vely and cooled by direct contact of the crystal mounting block with a liquid nitrogen reservoir. The temperature of the Au(lll) crystal was monitored directly by means of a... 

ESCA involves the measurement of binding energies of electrons ejected by interactions of a molecule with a monoenergetic beam of soft X-rays. For a variety of reasons the most commonly employed X-ray sources are Al and MgKol>2 with corresponding photon energies of 1486.6 eV and 1253.7 eV respectively. In principle all electrons, from the core to the valence levels can be studied and in this respect the technique differs from UV photoelectron spectroscopy (UPS) in which only the lower energy valence levels can be studied. The basic processes involved in ESCA are shown in Fig. 1. 

Photoelectron Spectroscopy. As a subdivision of electron spectroscopy, photoelectron or photoemission spectroscopy (PES) includes those instruments that use a photon source to eject electrons from surface atoms. The techniques of x-ray photoelectron spectroscopy (XPS) and uv photoelectron spectroscopy (UPS) are the principles in this group. Auger electrons are emitted also because of x-ray bombardment, but this combination is used infrequent-... 

In situ methods permit the examination of the surface in its electrolytic environment with application of the electrode potential of choice. Usually they are favored for the study of surface layers. Spectroscopic methods working in the ultra high vacuum (UHV) are a valuable alternative. Their detailed information about the chemical composition of surface films makes them an almost inevitable tool for electrochemical research and corrosion studies. Methods like X-ray Photoelectron Spectroscopy (XPS), UV Photoelectron Spectroscopy (UPS), Auger Electron Spectroscopy (AES) and the Ion Spectroscopies as Ion Scattering Spectroscopy (ISS) and Rutherford Backscattering (RBS) have been applied to metal surfaces to study corrosion and passivity. 

UV photoelectron spectroscopy (UPS) UV/electrons 0.5-20 electronic stmcture of valence band interfacial energetics... 

UV photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) are most commonly applied in this context. In the first method (UPS) electrons are excited by UV light (sources He I = 21.22 eV He II = 40.82 eV) and information on the electronic structure of the valence band region is obtained. The second method (XPS) provides information about the... 

UV photoelectron spectroscopy (UPS). Ethynyl- and allenyl-phosphine-boranes, along with methyl-, vinyl-, allyl-, and propargyl-phosphine-boranes, have been investigated using UV photoelectron... 

Surface Characterization Using Spectroscopic Techniques. The elemental composition and the oxidation states of surfaces are most frequently determined by x-ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), Auger spectroscopy, and high-resolution electron loss spectroscopy (HREELS). 

Low-work-function metals such as Ca, Mg, and A1 are commonly used as electron injection electrodes in organic LEDs, and thin Au films can be used for hole injection electrodes. The interfaces of these and other metals with PPV and its derivatives were investigated by several research groups using different techniques such as X-ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), transmission electron microscopy (TEM), quantum-chemical calculations, and electrical measurements. Some results are summarized in the following paragraphs for different metals. 

UV photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and low-energy electron diffraction (LEED) are most commonly applied in this context. In the first method, UPS, electrons are excited by UV light (sources He I = 21.22 eV He ii = 40.82 eV) and information on the electronic structure of the valence band region is obtained. The second method, XPS, provides information about the elemental composition and the valence states of the elements. Here, X-ray excitation is used (possible radiation sources MgK = 1253.6eV or A K = 1486.6 eV). In both methods, the emitted electrons are analyzed as current densities in dependence of their kinetic energy. Since the XPS signals depend not only on elemental composition but are also sensitive to the chemical environment of specific atoms, valuable information on a molecular structure can be obtained (see Chapter 8). LEED is used for the analysis of the geometric structure of the surface. Details of these and other methods applicable in combined electrochemical/UHV systems are very well discussed in a review article byjagermann [23]. 

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