UHV-Cleaved Single Crystal MgO(100) by Electron Energy Loss Spectroscopy

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.

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Valence electron energy-loss spectroscopy of ultrathin SrTiO3 films grown on silicon (100) single crystal

Applied Physics Letters ◽

10.1063/1.3364144 ◽

2010 ◽

Vol 96 (12) ◽

pp. 121914 ◽

Cited By ~ 4

Author(s):

Dong Su ◽

Bo Yang ◽

Nan Jiang ◽

M. Sawicki ◽

C. Broadbridge ◽

...

Keyword(s):

Energy Loss ◽

Single Crystal ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Valence Electron ◽

Electron Energy Loss

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Electron energy loss spectroscopy of adsorbed ethylene

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1986.0068 ◽

1986 ◽

Vol 318 (1541) ◽

pp. 141-161 ◽

Cited By ~ 37

Keyword(s):

Infrared Spectroscopy ◽

Energy Loss ◽

Single Crystal ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Supported Metal Catalysts ◽

Chemical Structures ◽

Π Complex ◽

Adsorbed Complex ◽

Electron Energy Loss

Electron energy loss spectroscopy (e.e.l.s.) provides an alternative method to infrared spectroscopy for studying the vibrational spectra of monolayers of chemisorbed molecules on single-crystal surfaces of metals. It has the advantages over infrared spectroscopy of considerably higher sensitivity, and the operation of two scattering mechanisms (dipolar and impact) that can be used to identify vibrations involving net motions parallel or perpendicular to the metal surface. It has the disadvantages with respect to infrared spectroscopy of lower attainable resolution and the necessity of the presence of only very low pressures (under 1 nbar) (0.1 m Pa) from molecules in the gas phase over the surface. Vibrational spectroscopy provides a powerful method for identifying the chemical structures of chemisorbed metal—adsorbate complexes. This is facilitated by an extensive existing vibrational spectroscopic literature. For work on metal surfaces, more recent infrared and Raman studies of ligands attached to metal clusters in com pounds of known structure have also been of substantial assistance. The scope of this type of surface analysis will be illustrated by a review of the extensive and interesting results now available by e.e.l.s. from this and a number of other laboratories for the adsorption of ethylene on a variety of metals and crystal faces, and over a range of temperatures. At low temperatures, ca. 100 K, ethylene adsorbs on different crystal faces as a π-complex or a di-σ adsorbed complex. At room tem perature, ca. 300 K , the low -tem perature species are transformed in some cases into an ethylidyne complex, CH 3 CM 3 (M = metal atom) or to a (C 2 H 2 )M 4 complex. More complex spectra, due to the presence of 4 different species, are obtained at room temperature by infrared transmission spectroscopy on finely divided oxide-supported metal catalysts. Three of these have been identified with the help of the e.e.l.s. results on metal single-crystal faces.

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