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Vibrational spectra from monolayer films of acrylic acid (CH2CHCOOH) on oxidized aluminum are obtained by inelastic electron tunneling spectroscopy and multiple reflection−absorption infrared spectroscopy. Analysis of these spectra shows that acrylic acid does not adsorb exclusively by a dissociative mechanism as do most carboxylic acids. Instead, at least two coadsorbed forms are observed: physisorbed molecular acid and chemisorbed acrylate ion. Rinsing the dosed surface with ethanol removes the physisorbed form while leaving undisturbed the chemisorbed form.

The technique of inelastic electron tunneling spectra (IETS) has been used to study the surface reaction of ethyl, isobutyl, and tert-butyl benzoates on alumina. The ethyl and isobutyl benzoates decompose to the corresponding alcohols where the net reaction accounts for the hydrolysis of the benzoate, and the ultimate products of chemisorption on alumina surface are detected to be the corresponding alkoxide anions. In the case of tert-butyl benzoate, the chemisorbed species on the alumina surface is benzoic acid rather than tert-butyl alcohol. In both cases, the surface reactions are identified as the dissociative chemisorption of the hydrolysis products of the original benzoate molecule

The basic theoretical and experimental concepts required for an understanding of inelastic electron tunneling spectroscopy (IETS) are presented. While most of the applications of IETS to date have centered on surface chemical analysis, the thrust of the present review is to present IETS as an alternative molecular spectroscopy. Comparison of IETS, IR, and Raman data obtained in the vibrational region of the spectrum and of IETS and absorption and reflectance data taken in the electronic region of the spectrum will be made. The difference in selection rules in IETS and in optical spectroscopy is emphasized. Numerous examples of optically forbidden transitions observed as strong bands in IETS are presented

Vibrational spectra of thin (0.2-1.0 nm) films of evaporated germanium on alumina surfaces have been measured by inelastic electron tunneling spectroscopy. The tunneling spectra of the evaporated Ge films were compared with those of the Si films. The tunneling spectra were also compared with the vibrational spectra of surface species on crystalline Ge formed from reactions with atomic hydrogen, water, and oxygen measured by high-resolution electron energy loss spectroscopy and multiple internal reflection infrared spectroscopy, and they showed the formation of germanium hydride species. Monohydride is predominantly formed in films prepared both in high vacuum (10 -6 Torr) and in an atmosphere of H 2 O (10 -5 Torr)

Vibrational spectra of thin (1-2 nm) films of evaporated silicon and silicon monoxide on alumina surfaces have been measured by inelastic electron tunneling spectroscopy. Analysis of the tunneling spectra of the Si and SiO films and comparison with the vibrational spectra of surface species on crystalline Si formed from reactions with hydrogen atoms, water, and oxygen measured by high-resolution electron energy loss spectroscopy and multiple internal reflection infrared spectroscopy showed the formation of silicon hydride species

Vibrational spectra of dimethyl, diethyl, and diphenyl phosphite on alumina and magnesia surfaces have been measured by inelastic electron tunneling spectroscopy. These dialkyl phosphites (O,O-dialkyl phosphonates) were adsorbed onto Al{sub 2}O{sub 3} and MgO surfaces from anhydrous benzene solutions by using a spin doping method. The tunneling spectra of phosphorous acid (phosphonic acid) on Al{sub 2}O{sub 3} have also been measured for comparison. Phosphorous acid reacts with surface OH groups of Al{sub 2}O{sub 3} by losing its protons and is adsorbed as phosphite anion (phosphonate dianion) onto the surface. Analysis of the tunneling spectra and comparison of the infrared and Raman spectra of the dialkyl phosphites give information about their molecular structures on Al{sub 2}O{sub 3} and MgO and a surface reaction on them. These dialkyl phosphites decompose by a reaction with the surface OH groups on Al{sub 2}O{sub 3} and MgO to give the adsorbed O-alkyl phosphonate monoanions and phosphonate dianion. The similarity of the tunneling spectra of dimethyl phosphite and that of phosphorous acid suggests that dimethyl phosphite decomposes rapidly to give preferentially the adsorbed phosphonate dianion on the surfaces.

Aluminum nitride films ranging in thickness from 0.4 to 25 nm were prepared by reactive ion-beam sputter deposition, utilizing a pure aluminum metal target and both pure nitrogen and 25% hydrogen-enriched nitrogen plasma. The 0.4-1.5-nm AlN films were studied by inelastic electron tunneling spectroscopy. Complementary vibrational techniques, specular reflectance and absorbance FT-IR spectroscopy, were used to analyze the thicker insulating films. The principal component of the insulating layers is AlN. Al-H, Al-N{sub 2}, and NH{sub 2} surface species are also present as minor components. Tunneling spectroscopy showed superior sensitivity over the optical methods in identifying various components of the AlN films. The quality of the tunneling barrier is enhanced by the presence of H{sub 2} during the AlN deposition.

Comparaison des spectres Raman de l'ion pentacyanopropenure en solution dans l'acetone, depose sur une surface de verre Vycor, sur une couche mince d'alumine ou sur une surface de Al oxyde (dans ce cas, par spectrometrie tunnel

The variation of line shape in inelastic electron tunneling spectroscopy (IETS) with temperature and modulation voltage is studied. Only normal metal tunneling is considered. Tunneling spectra were obtained from junctions of the type Al-Al{sub 2}O{sub 3}-KSCN-M, where M, the top metal, was Pb or Tl. The data presented cover the temperature region from 4 to 77 K. The experimental variation in line shape with modulation voltage ranging from 1.5 to 30 mV is also reported. A simplified line-shape function (Gaussian) is shown to satisfactorily predict line widths and peak intensities over a wide range of experimental conditions. The half-width at 1/e height of a single line is given by {Delta}, where {Delta} = ((a{sub 1}kT){sup 2} + (a{sub 2}V{sub f}){sup 2} + {Lambda}{sup 2}){sup {1/2}}, a{sub 1} = 3.3, a{sub 2} = 0.62, k = 0.0862 mV/K, {Lambda} is the intrinsic line width in millivolts, and V{sub f}is the 0 to peak modulation amplitude. This formula works best when 8kT {>=} V{sub f}.