Personal Research Database

Full Text: S\Sur Sci64, 425.pdf

Abstract: Three regimes of condensation have been observed between 74 and 80 K in the adsorption and desorption of a submonolayer film of xenon. The first one corresponds to thej condensation or evaporation of a two-dimensional (2D) ‘gas’, the second one to the growth of 2D crystal in the presence of the 2D gas, and the third one to the completion of the 2D crystal on the (0001) graphite face. Zero order kinetics for both adsorption and desorption is found in the large range of coverage (0.3 <  <0.9) where the two phases coexist on the surface. The activation energy of desorption of the 2D crystal is measured, its value (~6 kcal mole^-1) is in fair agreement with the value of the latent heat of evaporation of this phase (5.5 or 5.7 kcal mole^-1) determined previously. No activation energy of nucleation has been observed during the adsorption process. The growth rate is controlled by the incident flux only.

Jones, R.G. and Perry, D.L. (1978), The chemisorption of mercury on tungsten (100): Adsorption and desorption kinetics, equilibrium properties and surface structure. Surface Science, 71 (1), 59-74.

Full Text: S\Sur Sci71, 59.pdf

Abstract: The adsorption of mercury on W(100) has been studied by Auger spectroscopy, LEED and by work function and thermal desorption measurements. Mercury adsorbs at room temperature to form a (1×1) monolayer, with a sticking probability of unity and a heat of adsorption of 208±12kJ mol^-1. The coverage dependence of the work function change is interpreted according to an island growth mechanism which is shown to be consistent with the LEED observations. At higher temperatures, the equilibrium isotherms show evidence for attractive adsorbate-adsorbate lateral interactions. The isotherms were simulated using a localised adlayer model within the quasi-chemical approximation. This gave a nearest-neighbour pairwise interaction energy of 5.85 kJ mol^-1. The attractive interactions are shown to be consistent with the mechanism invoked to explain the desorption kinetics, which are zero order.

? Taylor, J.L., Ibbotson, D.E., and Weinberg, W.H. (1979), The chemisorption of oxygen on the (110) surface of iridium. Surface Science, 79 (2), 349-384.

Full Text: 1960-80\Sur Sci79, 349.pdf

Abstract: The chemisorption of oxygen on Ir(110) has been investigated under ultra-high vacuum conditions with thermal desorption mass spectrometry, contact potential difference measurements, Auger electron spectroscopy, and LEED. Oxygen may adsorb in three distinct chemical states: a molecularly chemisorbed species that is stable below 100 K, a dissociatively chemisorbed species, and a surface oxide that forms rapidly above 700 K. The oxide layer saturates at a coverage of 0.25 ML (1 ML = 9.6×10¹⁴atoms/cm²) and orders to form a (1×4) LEED pattern. Different LEED patterns of dissociatively chemisorbed oxygen are observed on clean and oxidized Ir(110). A p(2×2) pattern forms on the clean surface near 0.25 ML coverage whereas a c(2×2) pattern forms on the oxidized surface near 0.5 ML coverage. Oxygen desorbs molecularly from Ir(110) with an activation energy of 45–70 kcal/mole, decreasing continuously with increasing coverage. The adsorption kinetics are described by a second-order precursor model for surface temperatures between 300–700 K. Oxygen chemisorption is not activated since the initial sticking probabilities on the clean and the oxidized Ir(110) surfaces are equal to 0.28 and 0.4, irrespective of the surface temperature. The dipole moment and polarizability of dissociatively chemisorbed oxygen change at 0.25 ML coverage on the clean surface and at 0.5 ML coverage on the oxidized surface. Although the dipole moment for any coverage is independent of temperature, the polarizability is inversely proportional to temperature. The activation energy for the dissociation of molecularly chemisorbed oxygen is 8 kcal/mole.

Vlad, M. and Segal, E. (1979), A Kinetic analysis of Langmuir model for adsorption within the framework of Jovanovic theory: A generalization of the Jovanovic isotherm. Surface Science, 79 (2), 608-616.

Full Text: S\Sur Sci79, 608.pdf

Abstract: This paper presents a comparative kinetic analysis of the Langmuir and Jovanovic models for adsorption of gases on solid surfaces. Taking into account of the settling times distribution of the adsorbed molecules on the surface, the authors suggest a generalization of the Jovanovic isotherm.

Paunov, M. and Michailov, E. (1979), Mass-spectrometry of condensation of thin-layers on unlike substrates. I. Kinetics of adsorption and desorption of Ag on tungsten. Surface Science, 81 (2), 479-490.

Full Text: S\Sur Sci81, 479.pdf

Abstract: The adsorption and desorption kinetics of silver on clean polycrystalline tungsten were investigated with a mass-spectrometric technique. The deposition up to about 2 monolayers occurred without two-dimensional phase transformation. The thermal accommodation coefficient was found to be unity. The desorption energy and frequency factor for different coverages were determined. The bonding of silver atoms in the first monolayer was found to be localized. Additionally, thermal desorption experiments with linear heating rate were carried out.

Paunov, M. and Michailov, E. (1979), Massenspektrometrische untersuchungen der kondensation von dünnen schichten auf fremden unterlagen I. Kinetik der adsorption und der desorption von Ag auf W. Surface Science, 81 (2), 479-490.

Full Text: S\Sur Sci81, 479.pdf

Abstract: The adsorption and desorption kinetics of silver on clean polycrystalline tungsten were investigated with a mass-spectrometric technique. The deposition up to about 2 monolayers occurred without two-dimensional phase transformation. The thermal accommodation coefficient was found to be unity. The desorption energy and frequency factor for different coverages were determined. The bonding of silver atoms in the first monolayer was found to be localized. Additionally, thermal desorption experiments with linear heating rate were carried out.

Schönhammer, K. (1979), On the Kisliuk model for adsorption and desorption kinetics. Surface Science, 83 (2), L633-L636.

Full Text: S\Sur Sci83, L633.pdf

? Schwarz, J.A. and Kelemen, S.R. (1979), Adsorption-desorption kinetics of CO from clean and sulfur covered Ru(001). Surface Science, 87 (2), 510-524.

Full Text: 1960-80\Sur Sci87, 510.pdf

Abstract: The total uptake of CO, its adsorption kinetics and its desorption kinetics from clean and partially sulfur covered surfaces of the basal plane of ruthenium have been investigated. The method of desorption rate isotherms applied to the CO flash desorption spectra from these surfaces was used to evaluate the coverage dependence of the binding energy of CO as well as the effect of various levels of sulfur on this binding energy. Below a total surface concentration of 1 adsorbate atom per 3 surface Ru atoms, the binding energy and sticking probability of CO on the clean and sulfur covered surfaces are the same. Above this concentration of total adsorbates, the adsorption kinetics is the same on all surfaces studied, the binding energy decreases linearly with CO coverage while the magnitude of the decrease increases with sulfur coverage. The total uptake of CO depends on the amount of preadsorbed sulfur. At low coverages of sulfur, total CO uptake is effected by the excluded volume of sulfur. At higher coverages of sulfur (approaching 1/2 the maximum sulfur concentration on the clean surface) the site requirements of sulfur limits the amount of CO that can adsorb on the remaining surface, to the quantity of 1 adsorbate atom per 2 Ru atoms.

? Schwarz, J.A. (1979), Adsorption-desorption kinetics of H₂ from clean and sulfur covered Ru(001). Surface Science, 87 (2), 525-538.

Full Text: 1960-80\Sur Sci87, 525.pdf

Abstract: The adsorption and desorption kinetics of hydrogen from clean and partially sulflded surfaces of the (001) face of ruthenium were studied. Adsorption is dissociative and can be described by (1 − θ)2 kinetics. Desorption rate isothermal analysis of flash desorption spectra of hydrogen from the clean surface show that the desorption energy for hydrogen decreases linearly with increasing H2 coverage. The low coverage value of the desorption energy is 26 kcal/mole, decreasing to ≈11 kcal/mole at a coverage θH ≈ 0.8. The pre-exponential factor varies in sympathy with the desorption energy and thus the apparent second-order rate constant demonstrates a compensation effect. No hydrogen could adsorb on the first ordered overlayer of sulfur—the Ru(001)−(2×2)S. The LEED pattern was preserved which indicated that hydrogen does not displace sulfur from this surface. The effect of increasing amounts of sulfur on hydrogen adsorption is to rapidly suppress the saturation amount of hydrogen that can be adsorbed, sulfur acts to block dissociation sites for hydrogen adsorption and recombination sites for hydrogen desorption. The desorption rate parameters for hydrogen at fixed hydrogen coverage and increasing sulfur coverage decreases. The decrease parallels the decrease found for the clean surface with increasing hydrogen coverage.

? Behm, R.J., Christmann, K. and Ertl, G. (1980), Adsorption of hydrogen on Pd(100). Surface Science, 99 (2), 320-340.

Full Text: 1960-80\Sur Sci99, 320.pdf

Abstract: The energetic, kinetic and structural properties of hydrogen chemisorbed on a Pd(100) surface were studied by means of thermal desorption, work function and LEED measurements. Under the applied conditions no interference with bulk dissolution occurs and dissociative adsorption gives rise to a continuous increase of the work function by up to 0.20 eV. The dipole moment of the adsorbate complex is constant up to θ ≈ 0.9 and then increases until saturation at θ ≈ 1.35 (at 170 K) is reached. The formation of a second adsorbed state at high coverages manifests itself also by a low-temperature shoulder in the thermal desorption spectra and in the variation of the isosteric heat of adsorption, Ead, with coverage: Ead remains practically constant (24.5kcal/mole) up to θ ≈ 0.9 and then decreases. The sticking coefficient is initially rather high (s0 ≈ 0.5) and varies with coverage in a way which can be described by a precursor-state model. The preexponential factor for desorption is about 10⁻² cm² atom⁻¹ s⁻¹. Desorption follows second order kinetics only at very low coverages, at high θ it exhibits quasifirst order. This effect is attributed to the existence of lateral interactions between adsorbed hydrogen atoms which manifest themselves also in the appearance of a c(2×2) LEED pattern at low temperatures. The ‘extra’ diffraction spots attain their maximum intensity at θ = 0.5, and a structural model is proposed whereafter in this phase the H atoms occupy next-nearest neighboring adsorption sites with local fourfold symmetry. Order-disorder transitions were followed by recording the intensity of the half-order spots as a function of temperature at various coverages. The resulting phase diagram exhibits a critical temperature Tc = 260 K at θ = 0.5 and is slightly asymmetric with respect to this coverage. The data are analysed in terms of a lattice gas model and estimates for the pairwise interaction energies yield repulsion between nearest neighbors (w1 = 0.5 kcal/mole) and attraction between next-nearest neighbors (w2 = −0.3 kcal/mole). The additional operation of non-pair-wise interactions is made responsible for the asymmetric shape of the phase diagram. Whereas the adsorbed layer is obviously localized at T  270 K, a detailed analysis of the adsorption entropy reveals that for T  370 K a rather good description can be obtained with a model of delocalized two-dimensional translation.

Grüning, H. and Heiland, G. (1982), Binding and decomposition of organic-dye molecules on ZnO crystals. Surface Science, 122 (3), 569-587.

Full Text: S\Sur Sci122, 569.pdf

Abstract: Prism surfaces of ZnO crystals are prepared by various pretreatments as heating in ultrahigh vacuum (UHV), annealing in oxygen at pressures up to 10⁵ Pa, argon bombardment, cleavage in UHV. An organic dye is deposited by sublimation in UHV and the exposure (10¹²−10¹⁵ cm⁻² is recorded by means of a vibrating quartz. Adsorption and desorption studies including thermal desorption spectroscopy (TDS) are performed with variation of crystal temperature during deposition and of coverage. In these experiments the spectral distribution of absorption is used for the recording of coverage down to about 10¹² cm⁻², for the observation of ordering processes within the dye layer and for the detection of dye decomposition. By the various treatments the catalytic activity of the ZnO surface for decomposition of the dye molecules at temperatures above 350 K can be increased or decreased in a wide range. Possible sources of the activity are discussed. Molecules bound to a clean inactive ZnO surface desorb above 600 K. In contrast they come off already at 350 K if they are bound only to other molecules. A sticking coefficient is derived as a function of coverage at 470 K and compared with calculations after several adsorption models. The best fit is obtained by a precursor state model.

? Kołaczkiewicz, J. and Bauer, E. (1985), Clausius-Clapeyron equation analysis of two-dimensional vaporization. Surface Science, 155 (2-3), 700-714.

Full Text: 1985\Sur Sci155, 700.pdf

Abstract: The temperature dependence of the work function change caused by adsorption of Cu, Ag, Au, Ni and Pd on W(110) and of Ag and Au on W(211) is analyzed with the aid of the Clausius-Clapeyron equation. It is found that the heat of two-dimensional evaporation has a high and a low temperature value which indicates evaporation from smooth island edges at low temperature and rough edges at high temperature. A two-dimensional roughening transition is implied.

Daitzchman, C., Aharoni, C. and Ungarish, M. (1991), Effect of subsurface penetration on the kinetics of chemisorption. Surface Science, 244 (3), 362-370.

Full Text: S\Sur Sci244, 362.pdf

Abstract: Expressions describing the kinetics of chemisorption of gases by metallic surfaces are derived, assuming that the sorbate penetrates into a narrow subsurface selvedge adjacent to the surface. It is also assumed that in the selvedge, the energy of sorption decreases with depth and the transport of the sorbate is governed by diffusional laws. The model leads to plots of the sticking coefficient against the quantity adsorbed, in which the sticking coefficient is high and constant at low coverage but drops sharply at some higher coverage with a slope that decreases gradually. The initial part corresponds to a range in which the kinetics are determined by the rate of arrival of the sorbate from the gas phase to the solid phase, and the final part to a range in which the diffusional process is rate determining. The process may appear to be non-activated even when diffusion is activated. The coverage at which the sharp decrease of the sticking coefficient occurs is small when the pressure is high, when the selvedge is deep or indistinguishable from the bulk and when diffusion is slow.

Keywords: Adsorption, Nitrogen, Single-Crystal, Surfaces

Ertl, G. (1994), Reactions at well-defined surfaces. Surface Science, 299-300, 742-754.

Full Text: S\Sur Sci299, 742.pdf

Abstract: Early work (mainly by Langmuir) has erected the conceptual framework for chemical reactions occurring at well-defined solid surfaces and forming the basis for heterogeneous catalysis but experimental verification has been enabled only during the past three decades. My first contribution to Surface Science appeared in 1967 and concerned the interactions of various molecules with Cu single-crystal surfaces, mainly by using LEED. This technique revealed not only structural information, but also was applicable for studying kinetic phenomena as exemplified somewhat later with the catalytic oxidation of carbon monoxide on Pd(110). Some of the questions raised in this early work could be answered only quite recently or were revealed to be even more complex than anticipated. This holds in particular for catalytic reactions under steady-state conditions for which a wealth of phenomena of nonlinear dynamics, ranging from oscillatory or chaotic kinetics to spatio-temporal pattern formation, may occur.

? Tomellini, M. (1994), The initial uptake rate in precursor mediated adsorption. Surface Science, 303 (1-2), L354-L360.

Full Text: 1994\Sur Sci303, L354.pdf

Abstract: In the light of a kinetic model for precursor mediated adsorption, the steady state approximation for the transient surface coverage has been investigated. The expression for the experimental value of the initial uptake rate, derived by kinetics, is obtained in terms of the rate constants introduced in the model. The well-known formula for the initial sticking coefficient usually adopted for precursor mediated adsorption is found to be a limiting case of the general one. The constraints that allow for that expression to be valid have been established and discussed.

It is shown that under certain experimental conditions the initial uptake rate, as derived from adsorption data, could be representative of the molecule trapping coefficient into the precursor state. The trapping coefficient has also been described by means of a thermodynamic model and indicates that its temperature dependence is mainly dictated by the temperature dependence of the standard entropy change of adsorption.

Keywords Plus: Metal-Surfaces, Desorption, Kinetics, Pt(111), H₂, Co

Cordatos, H., Bunluesin, T. and Gorte, R.J. (1995), Study of CO, NO, and H₂ adsorption on model Pd/alpha-Al₂O₃(0001) catalysts. Surface Science, 323 (3), 219-227.

Full Text: S\Sur Sci323, 219.pdf

Abstract: We have examined the adsorption of CO, NO, and H₂ on alpha-Al₂O₃(0001)-supported, Pd particles using temperature-programmed desorption (TPD) in order to determine the effect of particle size on the desorption rates. For vapor deposition of Pd at 295 K, one obtains layer-by-layer growth of the Pd film. The film coalesces into a relatively uniform distribution of particles above similar to 600 K, as shown by TEM, with the particle sizes depending on the metal coverage. TPD curves for CO from all particle sizes are very similar to curves reported for bulk metals, with a main desorption feature at similar to 490 K and a second peak at similar to 375 K, however, the relative amount of CO desorbing from the low-temperature feature, assigned to linear CO, increases significantly for very small particles (similar to 1.6 nm). For NO, more than half of the molecules desorb intact from large particles (> 5 nm), with the remainder forming N₂O and N₂ at similar to 550 K and leaving adsorbed oxygen. The fraction of molecules which dissociate during TPD increases significantly for small particles and only N-2 is observed as a product above 600 K. For H₂ at 120 K, desorption occurs in two regions on large particles, between 250 and 400 K for surface hydrogen and at similar to 180 K for hydrogen from the bulk. The only significant difference on small particles is the absence of the 180 K state. These results are discussed in terms of their implications for Pd particle-size effects in catalysis.

Keywords: Temperature-Programmed Desorption, Palladium Particles, Supported Palladium, Carbon-Monoxide, Alpha-Al₂O₃(0001), Chemisorption, Oxide, Size, Overlayers, Oxidation

Karpov, S.Y. and Maiorov, M.A. (1996), Analysis of V-group molecules sticking to III-V compound surfaces. Surface Science, 344 (1-2), 11-22.

Full Text: S\Sur Sci344, 11.pdf

Abstract: Previous experiments carried out with the reflection mass spectrometry [12-15] are used to choose an adequate physical model of V-group molecules interaction with III-V-compound surfaces from the set of the possible ones. Comparison to the experimental data shows that a physisorption state plays an important role in the As-4 molecule adsorption on GaAs, AlAs, and InAs surfaces. No evidence of such a state for As-2 molecules was found. On the basis of the data on specie-separated outgoing arsenic fluxes a simple model has been proposed for the analysis of arsenic molecules adsorption, desorption and incident arsenic beam reflection. The desorption rate constant and the maximum sticking coefficient of the arsenic molecules were determined from the experimental data of Brennan et al. [J. Vac. Sci. Technol. A 10 (1992) 33]. It was found that the desorption rate constant was dependent on the surface reconstruction. The results of calculations performed using this model are compared to the data on sticking coefficient and arsenic coverage of the surface obtained in the independent experiments.

Keywords: Adsorption Kinetics, Aluminum Arsenide, Gallium Arsenide, Indium Arsenide, Physical Adsorption, Semi-Empirical Models and Model Calculations, Sticking, Energy Electron-Diffraction, Scanning Tunneling Microscopy, 100 Gaas Surfaces, Beam Epitaxy, Interaction Kinetics, Reflection, Stoichiometry, Reconstruction, Desorption, Growth

Tochihara, H. and Mizuno, S. (1996), Hybrid surface structures formed on Cu (001) and Ag (001) by alkali-metal adsorption. Surface Science, 357-358 (1-3), 10-18.

Full Text: S\Sur Sci357-358, 10.pdf

Abstract: We have determined the surface structure sequence 21--> 33--> 44 formed on Cu (001) with increasing Li coverage at 300 K by using low-energy electron diffraction analysis. Zn the 21 structure all Li atoms occupy substitutional sites, whereas the 33 and 44 structure similar to each other contain both substitutional Li atoms and Li adatoms. It is concluded that the surface accommodates additional Li atoms at the cost of the average adsorption energy in the sequence above. Another sequence 21--> 33 is found for Na adsorption on Ag (001) at room temperature. The 33 surface structure is considered to be the same one formed in Cu (001)-Li. Different sequence 21--> 31 is observed for K adsorption on Ag (001). Structure models for the 31 is proposed. We conclude that the 33 and 31 structures following the same 21 structure are formed basically due to the same cause and that different structures are realized owing to the size effect.

Aizawa, T., Hayami, W., Souda, R., Otani, S., Tanaka, T. and Ishizawa, Y. (1996), Molecular adsorption of oxygen on transition-metal carbide. Surface Science, 357-358 (1-3), 645-650.

Full Text: S\Sur Sci357-358, 645.pdf

Abstract: Room-temperature oxygen adsorption on NbC (111) and WC (<10 (1)over bar 0>) was studied by high-resolution electron energy loss spectroscopy and ultraviolet photoelectron spectroscopy. On NbC (111), oxygen is adsorbed dissociatively at the first stage. Above 210^-4 Pa.s of exposure, a molecular species appears, which shows O-O stretching and M-O-Obending vibrations at 122 and 89 meV. These peaks disappear at 300°C. When the NbC (111) surface is saturated by dissociative N atoms prior to the oxygen adsorption, the molecular adsorption occurs from the first stage. This suggests that the molecular adsorption is caused by a site-blocking mechanism. On the other hand, oxygen is adsorbed molecularly on WC (<10 (1) over bar 0>) from the first. The UPS shows a broad peak at-6.5 eV from the Fermi level, which is consistent with the 1 pi (u) and 3 sigma (g) orbitals of the molecular oxygen species.

Schilbe, P., Siebentritt, S., Pues, R. and Rieder, K.H. (1996), Adsorption of hydrogen and of oxygen on an open metalsurface-HREELS investigation at Ni(311). Surface Science, 360 (1-3), 157-170.

Full Text: S\Sur Sci360, 157.pdf

Abstract: The adsorption behavior of hydrogen and oxygen on the stepped Ni (311) surface has been investigated by HREELS. A series of metastable phases was found for hydrogen adsorption at low temperatures with a succession of different adsorption sites indicated by the following loss peaks: 55 and 149 meV for the threefold site, shirting with higher coverage to 65 and 155 meV, respectively, 40 and 90 meV for the fourfold site, shifting to 35 and 85 meV with coverage, and 110 and 124 meV for an additional site between close packed rows. Room temperature adsorption of hydrogen leads to the reconstruction of the surface with occupation of three-and fourfold sites, represented by loss peaks at 60 and 145 meV for the threefold site and 74 meV for the fourfold site. This phase is the thermodynamically stable one. Oxygen is most likely initially adsorbed on a bridge site (loss peak at 66 meV). The stepped surface is already oxidized at very low exposures to oxygen, as seen by the characteristic vibration for oxide islands at 55 meV and later by the Fuchs-Kliewer mode of NiO at 68 meV.

Gross, A. (1996), Dynamical quantum processes of molecular beams at surfaces: Dissociative adsorption of hydrogen on metalsurfaces. Surface Science, 363 (1-3), 1-10.

Full Text: S\Sur Sci363, 1.pdf

Abstract: Due to the improvement of computer power and the development of efficient algorithms it is now possible to combine high-dimensional quantum dynamical calculations of the dissociative adsorption of molecular beams with reliable ab-initio potential energy surfaces (PES). In this brief review two recent examples of such studies of the systems H₂/Cu (lll), where adsorption is hindered by a noticeable energy barrier, and H₂/Pd (100), where activated as well as non-activated paths to adsorption exist, are presented. The effect of lateral surface corrugation on the sticking probability in the tunneling and the classical regime and the role of additional parallel momentum are discussed in the context of the H₂/Cu (lll) results. For the system H₂/Pd (100) it is shown that the initial decrease of the sticking probability with increasing kinetic energy, which is usually attributed to a precursor mechanism, can be explained by dynamical steering. In addition, the influence of rotation on the adsorption and desorption dynamics is examined.

Dvorak, J., Borguet, E. and Dai, H.L. (1996), Monitoring adsorption and desorption on a metalsurface by optical non-resonant reflectivity changes. Surface Science, 369 (1-3), L122-L130.

Full Text: S\Sur Sci369, L122.pdf

Abstract: A linear optical reflection technique is demonstrated as a simple and non-intrusive means for monitoring the adsorption and desorption of carbon monoxide on Cu (100). The non-resonant reflectivity change induced by CO adsorption on copper is of the order of-1%, allowing submonolayer sensitivity of 0.01 ML to be achieved. The induced reflectivity change exists over a broad frequency range, and is found to correlate linearly with the coverage in both the infrared (lambda = 4.76 µm) and the visible (lambda = 632.8 nm). CO adsorption is found to proceed with a constant sticking coefficient up to a coverage of 0.5 ML, after which Langmuir adsorption kinetics are followed. The changes in the adsorption kinetics correlate quantitatively with structural changes in the CO monolayer. This technique monitors the surface coverage directly, and is simple and inexpensive to implement. As an optical surface probe it allows time-resolved measurements and can be extended to high-pressure environments.

Davydov, S.Y. and Tikhonov, S.K. (1997), On the cohesive approach to the calculation of d-metal on d-metal adsorption properties. Surface Science, 371 (1), 157-167.

Full Text: S\Sur Sci371, 157.pdf

Abstract: The binding (adsorption) energy of a d-metal atom adsorbed on a d-metalsubstrate is treated as a cohesive energy of the adatom. Adsorption, surface diffusion activation and adatom-adatom (s) interaction energies for all transition metals on W (110) are calculated on the basis of the Harrison-Wills theory of cohesion.

Aizawa, T., Hayami, W., Souda, R., Otani, S. and Ishizawa, Y. (1997), Hydrogen adsorption on transition-metal carbide (111) surfaces. Surface Science, 381 (2-3), 157-164.

Full Text: S\Sur Sci381, 157.pdf

Abstract: Vibrational frequency of H and D adsorbed on IVa and Va transition-metal carbide (TMC) (111) surfaces has been studied by high-resolution electron energy loss spectroscopy. Hydrogen (deuterium) was adsorbed dissociatively, showing the vibrational mode in an energy range of 110-120 (80-88) meV on ZrC (111), HfC (111) and NbC (111) surfaces, but at a much higher energy of 208 (149) meV on TaC (111). The former is similar to the case of H/TiC (111) consistent with three-fold hollow site adsorption. The latter seems too high to be explained by a variation of the force constant. It seems likely that on TaC (111), hydrogen is adsorbed on a different site from the other H/TMC (111) systems.

Bukhtiyarov, V.I., Carley, A.F., Dollard, L.A. and Roberts, M.W. (1997), XPS study of oxygen adsorption on supported silver: Effect of particle size. Surface Science, 381 (2-3), L605-L608.

Full Text: S\Sur Sci381, L605.pdf

Abstract: The suggestion that two types of oxygen species are necessary for ethylene epoxidation is investigated using a model carbon-supported silver catalyst. It is established that the relative populations of the nucleophilic and electrophilic oxygen species are strongly dependent on silver particle size, the nucleophilic oxygen only being observed for cluster sizes greater than 300 Angstrom. The observation that the two types of oxygen only co-exist on large silver particles is consistent with reported epoxidation rates for silver catalysts. (C) 1997 Elsevier Science B.V.

Keywords: Carbon, Chemisorption, Clusters, Oxygen, Silver, Soft X-Ray Photoelectron Spectroscopy, Ethylene Epoxidation, Partial Oxidation, Metal-Clusters, Surface, Spectroscopy, Mechanism, Catalysis, Ag(110)

Roelofs, L.D. and Fromowitz, D.B. (1997), Interacting depolarizable adatoms on a triangular lattice: A model for alkali metal adsorption on FCC (111) and HCP (0001) surfaces. Surface Science, 388 (1-3), 92-102.

Full Text: S\Sur Sci388, 92.pdf

Abstract: We investigate the phase diagram of adsorbed dipoles on a triangular lattice by means of Monte Carlo simulation. Our model incorporates depolarization and multiplicity of binding sites, effects thought to be important for describing the adsorption of alkali metal atoms on metalsurfaces. We successfully reproduce several important features of alkali-metal absorption systems including: the characteristic saturation in the work function decrease with coverage and the condensation behavior resulting from depolarization. We consider the T = 0 behavior for the general case and present the full condensation phase diagram for one set of parameters.

Fukutani, K. and Murata, Y. (1997), Photoexcited processes at metal and alloy surfaces: Electronic structure and adsorption site. Surface Science, 390 (1-3), 164-173.

Full Text: S\Sur Sci390, 164.pdf

Abstract: Photoexcited processes of NO and CO at photon energies ranging from 2.3 to 6.4 eV are investigated on Pt (111), Ni (111) and Pt (111)-Ge surface alloys by reflection-absorption infrared spectroscopy and resonance-enhanced multiphoton ionization. The branching between three competitive processes of desorption, recapture and dissociation upon laser irradiation is dramatically changed on the three surfaces. On Pt (111), NO is either photodesorbed or photodissociated depending on the coverage, while NO is exclusively photodissociated on Ni (111). UV-photon irradiation of NO on Pt (111)-Ge, on the other hand, induces only desorption of NO. Desorption of CO bound at the on-top site of Pt (111) is induced by laser irradiation. The electronic mechanism for photodesorption and competitive branching is discussed in terms of the electronic structure of the substrate and the adsorbate.

Koper, M.T.M. (1998), Isotherms of ionic adsorption at metal electrodes with coverage dependent lateral interactions due to mutual depolarization. Surface Science, 395 (1), L196-L200.

Full Text: S\Sur Sci395, L196.pdf

Abstract: Isotherms are calculated for a simple modal describing ions absorbing onto a metal electrode, taking into account the effect of mutual depolarization. By mutual depolarization is meant the progressive discharge of the ions with increasing coverage, leading to weaker dipole-dipole lateral interactions. The mean-field isotherm predicts sigmoidal parts in the isotherm in the region of ionic discharge, which may even develop into hysteresis and first-order phase transitions. The qualitative predictions of the mean-field theory, in particular the first-order phase transition, are reproduced by Monte-Carlo simulations, but only if the lateral repulsive interactions are long ranged, as is expected for electrostatic interactions.

Ahdjoudj, J. and Minot, C. (1998), Adsorption of H₂O on metal oxides: A periodic ab-initio investigation. Surface Science, 402-404, 104-109.

Full Text: S\Sur Sci402-404, 104.pdf

Abstract: We present ab-initio periodic Hartree-Fock calculations of water molecules on TiO₂ and MgO. On MgO, H₂O does not dissociate and is adsorbed parallel to the surface. The main interaction concerns the Mg from the surface and the p pair of the water. At saturation, adsorbate-adsorbate interactions favor the formation of an ice monolayer. On TiO₂ the water molecule is strongly adsorbed, dissociating to generate surfacehydroxyl groups. The reactivities of the two surfaces are compared and explained in terms of hard and soft acid and base theory.

Notes: highly cited

? Cai, W.B., Ren, B., Li, X.Q., She, C.X., Liu, F.M., Cai, X.W. and Tian, Z.Q. (1998), Investigation of surface-enhanced Raman scattering from platinum electrodes using a confocal Raman microscope: Dependence of surface roughening pretreatment. Surface Science, 406 (1-3), 9-22.

Full Text: 1998\Sur Sci406, 9.pdf

Abstract: In order to establish an appropriate surface roughening procedure for obtaining high-quality surface Raman spectra from Pt electrodes, various roughening conditions for the SERS from the adsorbed pyridine, thiocynate and hydrogen are assessed in terms of the corresponding surface Raman intensities, enhancement factors and surface homogeneity. The repetitive square-wave oxidation reduction cycle (SWORC) triangular-wave ORC (TWORC) and platinization have been performed in the present study. The enhancement factor (G) is calculated based on the confocal feature of a confocal microprobe Raman system, showing one to two orders of amplification of Raman signal for adsorbed pyridine on roughened Pt surfaces. The involvement of charge transfer (CT) enhancement is inferred from the SERS intensity-potential profiles that are dependent on excitation lines. In general, the Pt surfaces with different roughness factors (R) can be divided into three categories: (1) the mildly roughened surface with R of 20-30 seems more adequate for the study of SERS mechnism including calculation of G. (2) the moderately roughened surface with R ranging from 20 to 100, providing homogeneous morphologies: is suitable for investigating surface adsorption and reactions, (3) the highly roughened surface with R ranging From 100 to 300, with non-uniform morphologies, could only be used for investigating species having small Raman cross-sections such as hydrogen adsorption. (C) 1998 Elsevier Science B.V. All rights reserved.

Keywords: adsorption, AFM, Hydrogen, Platinum, Pyridine, Surface Raman Spectroscopy, Surface Roughening, Silver Electrode, Pyridine, Sers, Spectroscopy, Spectra, Spectroelectrochemistry, Roughness, Interface, Hydrogen, Metals

Pohl, M. and Otto, A. (1998), Adsorption and reaction of carbon dioxide on pure and alkali-metal promoted cold-deposited copper films. Surface Science, 406 (1-3), 125-137.

Full Text: S\Sur Sci406, 125.pdf

Abstract: The adsorption and reaction of carbon dioxide on pure and potassium-doped cold-deposited copper films has been investigated at low temperatures and under UHV conditions using surface enhanced Raman spectroscopy (SERS) and X-ray photoemission spectroscopy (XPS). On pure copper films, an activated anionic CO₂ delta-species has been observed in addition to a weakly physisorbed CO₂ species. On potassium-doped copper films, monodentate carbonate as well as carbon monoxide has been observed in addition to the two carbon dioxide species. After adsorbing CO₂ on preadsorbed hydrogen, weak features at 2841 and 2949 cm^-1 indicate the formation of formate. This result is compared to formate on pure copper films, synthesised by adsorbing formic acid on preoxidised copper films and subsequent annealing to 200 K.

Bełtowska-Brzezinska, M., Łuczak, T. and Holze, R. (1998), On adsorption of monohydric alcohols and diols at sp and sd metal electrodes. Surface Science, 418 (1), 281-294.

Full Text: S\Sur Sci418, 281.pdf

Abstract: A survey of studies on adsorption behaviour of monohydric alcohols and diols at the sp and sd metal electrode/aqueous solution interface is given. Particular attention is paid to the effect of the molecular structure of the surfactants (carbon chain length, number and arrangement of functional groups as well as multiple carbon-carbon bonds) on their interfacial arrangement and interactions.

Olivera, P.P., Patrito, E.M. and Sellers, H. (1998), Adsorption of sulfate, bisulfate and sulfuric acid on silver surfaces: A theoretical study. Surface Science, 418 (2), 376-394.

Full Text: S\Sur Sci418, 376.pdf

Abstract: The adsorption of sulfate, bisulfate and sulfuric acid is investigated on the 111, 110 and 100 surfaces of silver by means of ab initio calculations performed at the Hartree Fock + second order perturbation level of theory. We consider the following aspects of the adsorption process: binding energies on different surfaces and coordination sites, charge transfer and adsorbate relaxation. The adsorption of sulfate is studied in more detail on the three metal surfaces. Sulfate binding energies in the range 110-180 kcal/mol are calculated for the different surfaces and coordinations investigated. The highest binding energies were obtained for the more open 110 surface. On a given surface, coordination via three oxygen atoms is more stable than via only one. For bisulfate and sulfuric acid we obtained binding energies of 58 and 27 kcal/mol on the Ag(111) and Ag(100) surfaces, respectively. The charge transferred to the metal is 0.2 electrons for bisulfate and 0.4-0.6 electrons for sulfate. A linear relation was observed between the binding energy of H₂SO₄, HSO₄^- and SO₄^2- and the square of their effective charge on the surface. This behavior is characteristic of image charge interactions between ions and metal surfaces. The calculated binding energies for the anions allowed us to establish appropriate thermodynamic cycles which show that the acidity of bisulfate is enhanced when adsorbed on the surface. When sulfate and bisulfate are allowed to relax on the surface, the geometry of the ions changes according to the conservation of bond order on metal surfaces: while the bonds between coordinated oxygens and the metal surface strengthen, the bonds between these oxygens and sulfur weaken, The contribution of the relaxation energy to the binding energy of the anions is between 5 and 10 kcal/mol. (C) 1998 Elsevier Science B.V. All rights reserved.

Keywords: Ab Initio Quantum Chemical Methods and Calculations, Chemisorption, Single-Crystal Electrodes, Transform Infrared-Spectroscopy, Model Potential Method, In-Situ, Anion Adsorption, Pt(111) Electrode, Adsorbed Sulfate, Au(111) Electrode, Vibrational Spectroscopy, Polycrystalline Platinum

Prado, A.G.S., Miranda, B.S. and Jacintho, G.V.M. (2003), Interaction of indigo carmine dye with silica modified with humic acids at solid/liquid interface. Surface Science, 542 (3), 276-282.

Full Text: S\Sur Sci542, 276.pdf

Abstract: Two distinct humic acids, one extracted from Brazilian peat soil, HA(PS), and another one obtained from commercial source, HA(FL) were attachment onto silica gel modified with aminopropyltrimethoxysilane, producing two material named SiHA(PS) and SiHA(FL), respectively. The ability of these materials in removing indigo carmine dye from aqueous solution was followed through series of adsorption isotherms adjusted to modified Langmuir equation. The maximum number of moles adsorbed gave 6.820.1210^-4 and 2.150.1710^-4 mol g^-1 for SiHA(PS) and SiHA(FL), respectively. Same interactions were calorimetrically followed and the thermodynamic data showed endothermic enthalpic values: 12.310.55 and 24.691.05 kJ mol^-1 for SiHA(PS) and SiHA(FL) surfaces, respectively. Gibbs free energies for two adsorption processes of indigo carmine dye presented, negative values, reflecting dye/surface interactions must be accompanied by an increased in entropy values, which are 653 and 985 J mol^-1 K^-1 for SiHA(PS) and SiHA(FL) materials, respectively. The adsorption processes for both materials were spontaneous in nature although they presented an endothermic enthalpy for the interaction, resulting in an entropically favored process. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Aromatics, Silicon Oxides, Adsorption Isotherms, Heterogeneous Routes, Waste-Water, Gel, Substances, Adsorption, Cations, Separation, Oxidation, Surface

Fujimoto, N., Sinya, T., Seimiya, Y. and Asada, H. (2004), Adsorption of gases on SnS₂: trace of order–disorder phase transition of a honeycomb lattice gas. Surface Science, 572 (2-3), 283-295.

Full Text: S\Sur Sci572, 283.pdf

Abstract: We have made volumetric measurements of adsorption isotherm of Ar, Kr, O₂ and N₂ on a powder sample of tin disulfide SnS₂ in the temperature range of 77–90 K. Ar, Kr and O₂ exhibited pressure isotherms unusually bending at the coverage of 0.3–0.4 monolayer, while N₂ did not. The isotherms are analyzed by a quasi-chemical approximation theory developed for a honeycomb lattice gas with first nearest neighbor exclusion and with a small adsorption potential difference between the two (1×1)-1/2 sublattices. The unusual bending of the pressure isotherms is successfully explained as a trace of the order–disorder phase transition of second order that would take place in the honeycomb lattice gas if the two sublattices had the same adsorption potential. The adsorption potential difference is found to be at most of order of magnitude of the second nearest neighbor interaction energy.

Keywords: Adsorption Isotherms, Physical Adsorption, Surface Thermodynamics (Including Phase Transitions), Ising Models, Noble Gases, Sulphides, Oxygen, Powders

? Alessandrini, A., De Renzi, V., Berti, L., Barak, I. and Facci, P. (2005), Chemically homogeneous, silylated surface for effective DNA binding and hybridization. Surface Science, 582 (1-3), 202-208.

Full Text: S\Sur Sci582, 202.pdf

Abstract: We report on a method for covalent immobilization of 5’-thiol-modified single strand DNA probes, onto oxygen exposing surfaces by exploiting surface derivatization by 3-mercaptopropyltrimethoxysilane and subsequent intermolecular disulfide bond formation. The various steps in the formation of the molecular edifices have been characterized by X-ray photoelectron spectroscopy, quartz crystal microbalance and atomic force microscopy under liquid. Surface reaction kinetics of thiol-modified DNA probes with thiol-bearing silanes turned out to be a second-order one, possibly due to the presence of both free thiol and S-S dimers in solution. The ability of immobilized single strand DNA to bind the complementary strand has been tested and confirmed by quartz crystal microbalance measurements. The presented DNA immobilization method appears to be applicable to any surface bearing exposed hydroxyl moieties. (c) 2005 Elsevier B.V. All rights reserved.

Keywords: Surface Chemical Reaction, Oligonucleotide Immobilization, Atomic Force Microscopy, Quartz Crystal Microbalance, X-Ray Photoelectron Spectroscopy, Self-Assembled Monolayers, Atomic-Force Microscopy, Nucleic-Acids, X-Ray, Oligonucleotides, Immobilization, Microarrays, Films, Adsorption, Attachment

? Luo, M.F., MacLaren, D.A. and Allison, W. (2005), Migration and abstraction of H-atoms from the Cu(1 1 1) surface. Surface Science, 586 (1-3), 109-114.

Full Text: S\Sur Sci586, 109.pdf

Abstract: Isothermal measurements of the helium specular reflectivity from H–Cu(1 1 1) are used to demonstrate that adsorbed hydrogen is removed from the surface in an activated process according to first-order kinetics. The measurements were taken at low coverages with surface temperatures in the range of 210–245 K, where we derive an activation-energy of 64.3±1.3 kJ mol⁻¹. The observation allows us to rule out second-order, molecular desorption processes and supports the conclusion that the H atoms are transported from surface to sub-surface sites by an activated process. The results confirm an earlier suggestion that, in the low coverage limit, the sub-surface state for this system is more energetically favourable than other states. In addition, the measurements suggest abstraction processes take place with a probability of (4.3±1.0)s₀, where s₀ is the initial sticking probability.

Keywords: Adsorption Kinetics, Atom–Solid Scattering and Diffraction, Hydrogen Atom, Copper, Molecule–Solid Reactions, Surface Structure

? Jayaweera, P.M. and Jayarathne, T.A.U. (2006), Acid/base induced linkage isomerization of alizarin red adsorbed onto nano-porous TiO₂ surfaces. Surface Science, 600 (22), L297-L300.

Full Text: 2006\Sur Sci600, L297.pdf

Abstract: Diffuse reflectance FTIR studies indicate that alizarin red (1,2-dihydroxy-9-10-anthraquinone sulfonic acid) undergoes reversible acid/base induced linkage isomerization on nano-porous TiO₂ surfaces. It is also possible to convert molecules from surface orientation, ARS-(TiO_2-1,9) to the ARS-(TiO_2,-1,2) by thermal activation. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: Alizarin Red, Diffuse Reflectance FTIR, Titanium Dioxide, Photovoltaic Cells, Adsorption, Photosensitization, Complexes, Mechanism, Isomers, Oxide

? Khanom, F., Khan, A.R., Rahman, F., Takeo, A., Goto, H. and Namiki, A. (2007), Reactions of atomic oxygen with the D-covered Si(100) surfaces. Surface Science, 601 (14), 2924-2930.

Full Text: 2007\Sur Sci601, 2924.pdf

Abstract: We have studied D abstraction by O on the D/Si(1 0 0) surfaces using a continuous as well as pulsed O-beams. Both D-2 and D2O molecules are detected during O-exposure. The D-2 desorption is found to take place more efficiently on the monodeute ride/dideuteride surface than on the monodeuteride surface. The pulsed beam experiments exhibit occurrence of both a slow and a fast D-2 desorption. The D2O desorption is found to obey the second-order rate law in theta(0)(D) on the monodeuteride surfaces and 3.5th-order rate law on the monodeuteride/dideuteride surfaces. The D2O desorption is found to be governed also by the second-order rate law, however regardless of D coverage even on the monodeuteride/dideuteride surfaces. Possible mechanisms for the O-induced desorption from the D/Si(1 0 0) surfaces are discussed. (C) 2007 Elsevier B.V. All rights reserved.

Keywords: Abstraction, D-2, Desorption, Deuterium Adsorption, Experiments, Hydrogen Desorption, Kinetics, Law, Mechanisms, Monohydride, Occurrence, Oxidation, Oxygen, Rate, Second Order, Si(100), Si(111) Surfaces, Silicon Surface, Spectroscopy, Surface, Surfaces, Terminated Si(100), Water Formation

? Fan, Q.H., Shao, D.D., Hu, J., Wu, W.S. and Wang, X.K. (2008), Comparison of Ni²⁺ sorption to bare and ACT-graft attapulgites: Effect of pH, temperature and foreign ions. Surface Science, 602 (3), 778-785.

Full Text: 2008\Sur Sci602, 778.pdf

Abstract: Attapulgite was investigated to remove Ni²⁺ from aqueous solutions because of its strong sorption ability. Herein, the sample of attapulgite was modified with ammonium citrate tribasic (ACT) and used as an adsorbent to remove Ni²⁺ from aqueous solutions. XRD and FTIR analysis indicated that ACT was successfully grafted on attapulgite surfaces. The results indicated that ACT-attapulgite was better than bare attapulgite in the removal of Ni²⁺ from aqueous solutions. Sorption of Ni²⁺ on ACT-attapulgite was mainly dominated by ion exchange or outer-sphere complexes at low pH values, and by inner-sphere complexes or surface precipitation at high pH values. The thermodynamic data indicated that the sorption of Ni²⁺ to ACT-attapulgite hybrids was an endothermic process and was enhanced with increasing temperature. ACT-attapulgite is a suitable material for the preconcentration of Ni²⁺ from large volume of solutions and can be used in wastewater treatment because of its negative surface charge and large surface areas. (C) 2007 Elsevier B.V. All rights reserved.

Keywords: Attapulgite, Ni²⁺, Sorption, Thermodynamic Data, ACT, Aqueous-Solution, Equilibrium Parameters, Compacted Bentonite, Carbon Nanotubes, Batch Adsorption, Capillary Method, Humic-Acid, Maya-Blue, Palygorskite, Ni(II)

? Bhatta, R.P., Thoms, B.D., Alevli, M. and Dietz, N. (2008), Desorption of hydrogen from InN(0001) observed by HREELS. Surface Science, 602 (7), 1428-1432.

Full Text: 2008\Sur Sci602, 1428.pdf

Abstract: The kinetics of isothermal desorption of hydrogen from InN(000 (1) over bar) have been investigated using surface vibrational spectroscopy. Reductions in intensity of the N-H stretching and bending vibrations in high resolution electron energy loss spectra (HREELS) upon annealing indicated loss of surface hydrogen and was attributed to recombinative desorption. Hydrogen completely desorbs from the InN surface upon annealing for 900 s at 425°C or upon annealing for 30 s at 500°C. Surface hydrogen coverage was determined using the intensity of the N-H stretching vibrational loss peak. Fitting the coverage versus temperature for anneals of either 30 or 900 s indicated that the desorption was best described by second-order desorption kinetics with an activation energy and pre-exponential factor of 1.30.2 eV and 10(-7.31.0) cm²/s, respectively. In addition to thermal desorption, an increase in the carrier concentration in the film was also observed upon annealing to 450°C or higher as shown in HREELS by a shift of the conduction band plasmon excitation to higher energy. (c) 2008 Elsevier B.V. All rights reserved.

Keywords: Activation, Activation Energy, Adsorption, Chemical-Vapor-Deposition, Decomposition, Desorption, Desorption Kinetics, Electron Energy Loss Spectroscopy, Gan, Group-III Nitrides, Growth, Hydrogen, Indium Nitride, Inn, Kinetics, Layers, Rights, Spectroscopy, Surface Electron Accumulation, Temperature, Thin-Films

? Rinaldi, P., Bulnes, F., Ramirez-Pastor, A.J. and Zgrablich, G. (2008), Monte Carlo study of multicomponent adsorption on triangular lattices. Surface Science, 602 (10), 1783-1794.

Full Text: 2008\Sur Sci602, 1783.pdf

Abstract: The adsorption process of interacting binary gas mixtures containing particles A and B on triangular substrates is studied through grand canonical Monte Carlo simulation in the framework of the lattice-gas model. The energies involved in the adsorption process are four: (1) epsilon(0), interaction energy between a monomer (type A or B) and a lattice site, (2) W-AA, nearest-neighbor interaction energy between two A particles, (3) W-AB (=W-BA), nearest-neighbor interaction energy between an A particle and a B particle and (4) W-BB, nearest-neighbor interaction energy between two B particles. The process is monitored through partial and total isotherms, differential heats of adsorption and energy of the system, which appear as very sensitive to all lateral interactions. We focus on the case of repulsive lateral interactions, where a rich variety of structural orderings are observed in the adlayer, depending on the value of the parameters W-AA, W-AB and W-BB. Results are rationalized through the determination of the phase diagrams characterizing second order phase transitions in the system. A nontrivial interdependence between the partial surface coverage of both species is observed. (C) 2008 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Binary-Mixtures, Calorimetric Heats, Emery-Griffiths Model, Framework, Gas, Gas Mixture Adsorption, Heterogeneous Surfaces, Interaction, Ising-Model, Isotherms, Lattice-Gas Models, Model, Monte Carlo, Monte Carlo Simulation, Multicritical Phase-Diagrams, Particles, Rights, Second Order, Second-Order, Silicalite, Simulation, Transition

? Khan, A.R., Narita, Y., Namiki, A., Kato, A. and Suernitsu, M. (2008), Adsorption and abstraction of atomic hydrogen on the Si(110) surfaces. Surface Science, 602 (11), 1979-1986.

Full Text: 2008\Sur Sci602, 1979.pdf

Abstract: The abstraction reaction of D adatoms by H atoms have been investigated on the Si(1 10) surfaces. The direct abstraction to form HD molecules obeys a second-order rate law in D coverage 0(D), On the other hand, the indirect abstraction to form D-2 molecules obeys a fourth-order rate law in 0(D). In addition to the direct abstraction, indirect abstraction to form HD molecules is also included due to piled H adatoms during H exposure. It is found that the indirect abstraction is promoted on the surfaces saturated with dideuterides, suggesting that dideuterides (dihydrides) play a significant role in the indirect abstraction paths. The kinetics of the abstraction reactions on the Si(1 10) surfaces look similar to those on the Si(1 00) surface. However, the delayed D-2 desorption exhibits time profiles different from those on the Si(1 00) surfaces. (c) 2008 Elsevier B.V. All rights reserved.

Keywords: 573 K, Adsorption, Amorphous-Silicon, Atom-Solid Interactions, Desorption, Desorption-Kinetics, Deuterium, Eley-Rideal Mechanism, Exposure, FTIR, H-Atoms, H-Sticking, HD, Hot Complex, Hydrogen, Kinetics, Law, Momentary Coverages, Phase, Plasma Processing, Rate Law, Reconstruction, Rights, Scanning-Tunneling-Microscopy, Second Order, Second-Order, Si(100) Surfaces, Thermal Desorption, Time Response

? Kunz, S., Schweinberger, F.F., Kwon, G., Kiermaier, J., Le Moal, S., Henry, C. and Heiz, U. (2010), Adsorption studies of trichloroethylene (TCE) on MgO(100)/Mo(100). Surface Science, 604 (23-24), 2184-2189.

Full Text: 2010\Sur Sci604, 2184.pdf

Abstract: Employing ultraviolet photoelectron spectroscopy (UPS He I) the more surface sensitive metastable Impact electron spectroscopy (MIES) and temperature programmed desorption (TPD) measurements of the adsorption properties of the pollutant trichloroethylene (TCE) on thin MgO(100) films grown on a Mo (100) single crystal have been investigated From TPD spectra of different coverages it is concluded that TCE interacts only weakly with MgO which is attributed to physisorption For increasing coverages a change from one peak to two peaks in the TPD spectra one at higher the second at lower temperatures with respect to the single peak is detected Additionally the observation of a local minimum for the work function (WF) for both MIES and UPS spectra is presented Such a local minimum has been reported previously for the adsorption of metals with outer s valence electrons on transition metal substrates and adsorption of metals with outer s valence electrons on metal oxide films Herein we present the first WF minimum observed for a system of organic molecules adsorbed on an insulating surface Two different models are discussed in order to understand the presented results (C) 2010 Elsevier B V All rights reserved.

Keywords: Adsorption, Alkali-Metal Adsorption, Clusters, Desorption, Ionization Electron-Spectroscopy, Mechanism, Metals, MgO, MgO Surfaces, Mies, Models, Molecules, Oxide, Oxide Surfaces, Physisorption, Properties, System, TCE, Temperature, Thin-Films, TPD, Trichloroethylene, Trichloroethylene (TCE), Ultraviolet Photoelectron, Ups (He I)