Energy electron loss spectroscopy study

Employing TERS in UHV systems There are a number of surface science tools available for samples in UHV which allow us to characterize the state of a surface. Surface and adlayer structures can be determined by LEED (low electron energy diffraction) as weU as by SPM (scanning probe microscopy) techniques. While the kind of chemical interactions can be studied, for example, with AES (Auger electron spectroscopy), EELS (energy electron loss spectroscopy) permits the identification of the chemical nature of the adsorbed species. TERS, on the other hand, may provide similar but also complementary information on the chemical identity under UHV conditions. As an additional advantage, TERS and SPM permit the identification and characterization of the spatial region from which this information is accumulated. 

Chen PJ, Colaianni ML, Wallace RM, Yates JT Jr (1991) Dissociative adsorption of PH3 on Si( 111) — (7x7) a high resolution electron energy loss spectroscopy study Surf. Sci. 244 177-184... 

Miyano T, Sakisaka Y, Komeda T, Onchi M (1986) Electron energy-loss spectroscopy study of oxygen chemisorption and initial oxidation of Ee(llO). Surf Sci 169 197... 

In these examples, the metastable H2 does not actually undergo electron loss because the Na or Mg Ion "retrieves the electron as the complex dissociates leaving the H2 vlbratlonally excited and the Na or Mg atom In Its ground state. Recent work on electron transmission spectroscopy studies of unsaturated hydrocarbons (24) demonstrates that electronic shape resonances may be essentially ubiquitous In chemical systems which possess low-energy vacant orbitals and the availability of electron density to enter such orbitals. 

Pellegrino, O. et al.. High-resolution electron energy loss spectroscopy studies on the electronic shucture of quinquethiophene (5T) and sexithiophene (6T) Bhns, Thin Solid Films 329, 291-294, 1998. 

HREELS High-resolution electron energy loss spectroscopy Study of adsorbed species... 

Fig. 1. Experimental techniques available for surface studies. SEM = Scanning electron microscopy (all modes) AES = Auger electron spectroscopy LEED = low energy electron diffraction RHEED = reflection high energy electron diffraction ESD = electron stimulated desorption X(U)PS = X-ray (UV) photoelectron spectroscopy ELS = electron loss spectroscopy RBS = Rutherford back scattering LEIS = low energy ion scattering SIMS = secondary ion mass spectrometry INS = ion neutralization spectroscopy.

B.E. Koel, J.E. Crowell, C.M. Mate, and G.A. Somoijai. A High Resolution Electron Energy Loss Spectroscopy Study of the Surface Structure of Benzene Adsorbed on the Rhodium (111) Crystal Face. J. Chem. Phys. 88 1988 (1984). 

The X-ray diffraction patterns for Ge02 (H) and Ge02 (T) have been accurately determined and can be used to identify films as thin as 500 A (using low angle diffraction). Here again, the monoxide phase cannot be identified by this means since no diffraction pattern has been observed for that phase. Some other non-destructive techniques have been used such as low energy electron diffraction (LEED), electron loss spectroscopy (ELS), Raman scattering, etc. but usually they are so sensitive to contamination that the results cannot easily be used for simple phase identification. Such techniques are therefore more useful for physical property studies. 

Chemisorption and subsequent decomposition of bromomethane on a Mg(OOOl) single crystal surface under ultra high vacuum conditions were studied using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), temperature-programmed decomposition (TPD) and high-resolu-tion electron loss spectroscopy (EELS). 

M. Jo, Y. Kuwahara, M. Onchi, M. Nishijima, Oxygen-adsorption on Pd (110) at 300-k-low-energy electron-diflraction and electron-energy loss spectroscopy studies. Chem. Phys. Lett. 131(1-2), 106-111 (1986)... 

In recent years there is a growing interest in the study of vibrational properties of both clean and adsorbate covered surfaces of metals. For several years two complementary experimental methods have been used to measure the dispersion relations of surface phonons on different crystal faces. These are the scattering of thermal helium beams" and the high-resolution electron-energy-loss-spectroscopy. ... 

Knowledge of the stracture and bonding of molecnles to snrfaces has been obtained from such techniques as LEED, electron energy-loss spectroscopy (EELS), secondaiy-ion mass spectrometry (SIMS), infrared spectroscopy (IRS), Raman spectroscopy, and NMR spectrometiy. The scope of snch studies needs to be greatly expanded to include the effects of coadsorbates, promoters, and poisons. Greater emphasis should be given to developing new photon spectroscopies that would permit observation of adsorbed species in the presence of a gas... 

The reactions of ethylene, water, and methanol with coadsorbed oxygen on Pdf 100) were studied with temperature programmed reaction spectroscopy (TPRS) and high resolution electron energy loss spectroscopy (EELS). 

Analytical electron microscopy permits structural and chemical analyses of catalyst areas nearly 1000 times smaller than those studied by conventional bulk analysis techniques. Quantitative x-ray analyses of bismuth molybdates are shown from lOnm diameter regions to better than 5% relative accuracy for the elements 61 and Mo. Digital x-ray images show qualitative 2-dimensional distributions of elements with a lateral spatial resolution of lOnm in supported Pd catalysts and ZSM-5 zeolites. Fine structure in CuLj 2 edges from electron energy loss spectroscopy indicate d>ether the copper is in the form of Cu metal or Cu oxide. These techniques should prove to be of great utility for the analysis of active phases, promoters, and poisons. 

The first two advantages listed above allow an optical method like transmission or reflection IR spectroscopy to be used for studies which would be impossible for a widely used competitive technique, electron energy loss spectroscopy (EELS). EELS must... 

Ammonia oxidation was a prototype system, but subsequently a number of other oxidation reactions were investigated by surface spectroscopies and high-resolution electron energy loss spectroscopy XPS and HREELS. In the case of ammonia oxidation at a Cu(110) surface, the reaction was studied under experimental conditions which simulated a catalytic reaction, albeit at low... 

Vibrational spectroscopy provides the most definitive means of identifying the surface species arising from molecular adsorption and the species generated by surface reaction, and the two techniques that are routinely used for vibrational studies of molecules on surfaces are Infrared (IR) Spectroscopy and Electron Energy Loss Spectroscopy (HREELS) (q.v.). 

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