Identification of adsorbed species at metal surfaces by electron energy loss spectroscopy (EELS)

1981 ◽  
Vol 26 (1) ◽  
pp. 1-18 ◽  
Author(s):  
B. A. Sexton
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Metal Surfaces ◽  
Adsorbed Species ◽  
Electron Energy Loss

The use of thermal desorption and electron energy loss spectroscopy for the determination of the structures of unsaturated hydrocarbons chemisorbed on metal single-crystal surfaces I. Alk-1-enes on Pt(111)

1986 ◽  
Vol 405 (1828) ◽  
pp. 1-25 ◽  
Keyword(s):  
Energy Loss ◽  
Single Crystal ◽  
Electron Energy ◽  
Thermal Desorption ◽  
Electron Energy Loss Spectroscopy ◽  
Hydrocarbon Chain ◽  
Adsorbed Species ◽  
Single Crystal Surfaces ◽  
Mass Spectral ◽  
Electron Energy Loss

Thermal desorption combined with mass spectral analysis is used to determine the elemental composition, as a function of temperature, of the adsorbed monolayers of the alk-1-enes, propene, but-1-ene, pent-1-ene and isobutene chemisorbed on the (111) face of a Pt single crystal. Vibrational electron energy loss spectroscopy (EELS) is used to assign structures to the surface species adsorbed at different temperatures. At the lowest temperatures (below 200 K) it is concluded that in each case these alk-1-enes are bonded to the metal surface in the form of di-σ-bonded non-dissociatively adsorbed species. The simplicity of the EEL spectrum from the species derived from isobutene provides additional support for an earlier assignment to the di-σ-adsorbed species for ethylene on Pt(111). At ca . 300 K the EEL spectra and thermal desorption data are consistent with the presence of alkylidyne, M 3 C(CH 2 ) n CH 3 (M = metal; n = 1, 2 or 3) or M 3 CCH(CH 3 ) 2 structures for the chemisorbed species respectively, (M = metal atom). For temperatures above 300 K the thermal desorption results show substantial further loss of hydrogen, a process which commences at lower temperatures the longer the hydrocarbon chain. Near 450 K the thermal desorption data indicate average C:H compositions of approximately C 3 H 2 for the species derived from propene, C 4 H 2 from but-1-ene, and C 4 H 4 from isobutene. The EEL spectra are used to indicate the remaining hydrocarbon functional groups present at this and at higher temperatures. Above 450 K closely similar spectra were obtained from all the straight-chain butenes including the cis - and trans -but-2-enes and buta-1, 3-diene whose spectra are discussed in more detail in the following paper. The EEL spectra indicate the occurrence of C—C bond breaking in general above ca . 500 K, the onset temperatures being somewhat dependent on the adsorbed hydrocarbon.

Data Acquisition and Handling Unit for a Quantitative Use of Electron Energy Loss Spectroscopy

1977 ◽  
Vol 35 ◽  
pp. 232-233 ◽  
Author(s):  
P. Trebbia ◽  
P. Ballongue ◽  
C. Colliex
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Single Channel ◽  
Detection System ◽  
Surface Barrier ◽  
Solid State Detector ◽  
Electrostatic Mirror ◽  
Electron Energy Loss

An effective use of electron energy loss spectroscopy for chemical characterization of selected areas in the electron microscope can only be achieved with the development of quantitative measurements capabilities.The experimental assembly, which is sketched in Fig.l, has therefore been carried out. It comprises four main elements.The analytical transmission electron microscope is a conventional microscope fitted with a Castaing and Henry dispersive unit (magnetic prism and electrostatic mirror). Recent modifications include the improvement of the vacuum in the specimen chamber (below 10-6 torr) and the adaptation of a new electrostatic mirror.The detection system, similar to the one described by Hermann et al (1), is located in a separate chamber below the fluorescent screen which visualizes the energy loss spectrum. Variable apertures select the electrons, which have lost an energy AE within an energy window smaller than 1 eV, in front of a surface barrier solid state detector RTC BPY 52 100 S.Q. The saw tooth signal delivered by a charge sensitive preamplifier (decay time of 5.10-5 S) is amplified, shaped into a gaussian profile through an active filter and counted by a single channel analyser.

Trends in Electron Energy Loss Spectroscopy

1977 ◽  
Vol 35 ◽  
pp. 228-229
Author(s):  
C. Colliex ◽  
P. Trebbia
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Materials Science ◽  
Analytical Technique ◽  
Recent Developments ◽  
Quantitative Results ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Primary Electrons

The physical foundations for the use of electron energy loss spectroscopy towards analytical purposes, seem now rather well established and have been extensively discussed through recent publications. In this brief review we intend only to mention most recent developments in this field, which became available to our knowledge. We derive also some lines of discussion to define more clearly the limits of this analytical technique in materials science problems.The spectral information carried in both low ( 0<ΔE<100eV ) and high ( >100eV ) energy regions of the loss spectrum, is capable to provide quantitative results. Spectrometers have therefore been designed to work with all kinds of electron microscopes and to cover large energy ranges for the detection of inelastically scattered electrons (for instance the L-edge of molybdenum at 2500eV has been measured by van Zuylen with primary electrons of 80 kV). It is rather easy to fix a post-specimen magnetic optics on a STEM, but Crewe has recently underlined that great care should be devoted to optimize the collecting power and the energy resolution of the whole system.

Signal/Noise Ratio and Elemental Detectivity by Eels

1982 ◽  
Vol 40 ◽  
pp. 488-489
Author(s):  
R. F. Egerton
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Elemental Analysis ◽  
Electron Energy Loss Spectroscopy ◽  
Emission Spectroscopy ◽  
X Ray ◽  
Signal Noise ◽  
Characteristic Signal ◽  
Noise Ratio ◽  
Electron Energy Loss

An important parameter governing the sensitivity and accuracy of elemental analysis by electron energy-loss spectroscopy (EELS) or by X-ray emission spectroscopy is the signal/noise ratio of the characteristic signal.

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