M Bjorkqvist

Hydrogen adsorption on the Pt(111)(3 × 3)R30°-Sn surface alloy studied by high resolution core level photoelectron spectroscopy

Investigation of the clean and atomic hydrogen covered Pt(111)(root 3 x root 3)R30 degrees-Sn surface alloy has been carried out using high resolution core level photoelectron spectroscopy, The Pt 4(7/2) spectrum recorded from the clean surface alloy shows a single surface peak shifted - 0.25 eV relative to the bulk. Its interpretation by means of a thermodynamical model using Born-Haber cycles confirms the surface alloy model. Adsorption of H does not change the line shape of the Sn 4d core level while a new surface component shifted by 0.59 eV compared to the bulk peak appears in the Pt 4(7/2) spectrum. These results are discussed in the light of the thermodynamical calculations, H atoms are believed to bind only to Pt atoms, and their adsorption site seems to be influenced by the tin present in the surface layer.

Etching and a disordered overlayer on the Ge(100)-S surface

High resolution core level photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) have been used to study the adsorption and desorption of S on and off the Ge(100) surface. The pr ...

Observation of true c(8 × 2) symmetry in scanning tunnelling microscopy images of the clean InSb(001) surface

Abstract Filled and empty state scanning tunnelling microscopy images of the sputtered and annealed InSb(001) surface are presented. The sputter-anneal preparation generates a surface with two distinct phases. The dominant phase possesses a unit cell with true c(8 × 2) symmetry, whereas the other phase is attributed to an asymmetric 1 × 3 reconstruction. The presence of a c(8 × 2) unit cell in filled state images is in contrast to previous reports, which identified only a 4 × 1 unit cell. The true c(8 × 2) symmetry further indicates, the available structural model is used as a guide, that the current interpretation of features in filled state images is incorrect. This result may necessitate a reevaluation of the structural model for the InSb(001)-c(8 × 2) surface.

Iodine reaction and passivation of the Ge(111) surface

Abstract The Ge(111)-I surface has been studied at different I coverages ranging from 0.05 ML up to saturation, and different annealing temperatures, using photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM). At saturation the surface is covered with I in the top site and GeI2 species in the bridge site, coexisting with small islands/clusters comprising GeI2, giving a total coverage of I in GeIx species of 1.15 ML. The chemically induced shifts in the Ge 3d core level are 0.39 eV per attached I atom. The coverage determined from the I 4d core level is higher than 1.15 ML, which we explain by the presence of I not bound to Ge. Annealing at 200°C decreases the iodine coverage, whereas the I 4d and Ge 3d line profiles are practically unchanged. Further heating desorbs the iodide species and restores the virgin c(2 × 8) structure.

Ge/(111)3x1:K/Sn; On the influence of tin substitution in a metal induced 3x1 reconstruction

Go-adsorption of tin and potassium is found to induce a 3x1 reconstruction on the Ge(lll) surface. A very small amount of tin influences the Ge 3d core level spectra substantially compared to the G ...

Nitride formation and dangling-bond passivation on Si(111)-(7 × 7) with NH3

Thermal nitridation of the Si(111)-(7 x 7) reconstructed surface with ammonia has been investigated using scanning tunneling microscopy (STM). True nitride formation in the form of ring-like struct ...

Hydrogen adsorption on the -Sn surface alloy studied by high resolution core level photoelectron spectroscopy

Investigation of the clean and atomic hydrogen covered Pt(111)(root 3 x root 3)R30 degrees-Sn surface alloy has been carried out using high resolution core level photoelectron spectroscopy, The Pt 4(7/2) spectrum recorded from the clean surface alloy shows a single surface peak shifted - 0.25 eV relative to the bulk. Its interpretation by means of a thermodynamical model using Born-Haber cycles confirms the surface alloy model. Adsorption of H does not change the line shape of the Sn 4d core level while a new surface component shifted by 0.59 eV compared to the bulk peak appears in the Pt 4(7/2) spectrum. These results are discussed in the light of the thermodynamical calculations, H atoms are believed to bind only to Pt atoms, and their adsorption site seems to be influenced by the tin present in the surface layer.

Surface electronic structure of GaAs(311)A studied by angle-resolved photoelectron spectroscopy

Abstract The valence and core electronic structure of the sputtered and annealed 1 × 1 periodic GaAs(311)A surface has been studied by angle-resolved photoelectron spectroscopy. Five surface bands are identified and their dispersions along high symmetry lines in the surface Brillouin zone are mapped out. While electron-counting indicates a metallic surface, the experiment show no evidence for partly occupied surface bands. Analysis of the core level spectra reveals one As and two Ga surface shifted components. The results are discussed in terms of surface geometry models.

InSb(1̄ 1̄ 1̄)3×1: New surface reconstruction

Scanning tunneling microscopy studies of the InSb(111) surface have revealed highly ordered 3×1 symmetry reconstructions. The structures are produced at high annealing temperatures and are believed to be driven by the deficiency of Sb in the surface layer. The proposed model for the reconstruction involves two distinct structures: One constitutes a missing Sb row in the topmost double layer, and one comprises two missing Sb rows with an additional missing row of In.

InSb(211) studied by photoelectron spectroscopy and scanning tunneling microscopy

Abstract The two inequivalent sides of InSb(211) have been studied by scanning tunneling microscopy (STM), angle-resolved photoelectron spectroscopy (ARPS) and low-energy electron diffraction (LEED). Despite identical sputtering–annealing preparations, the surface qualities are very different in the two cases. The (211)A surface has a high degree of disorder reflected by a poor (1×1) LEED pattern and a lack of well-defined surface-induced features in valence band ARPS. In STM, this surface shows small (211) terraces with a high density of steps. The In core level spectrum of (211)A suggests presence of a metallic component. In contrast, the (211)B surface is ordered, with large flat terraces, and shows a sharp (1×1) LEED pattern. The In and Sb core level spectra are well fitted with one surface shifted component and show no sign of metallic In. In the valence band spectra, three surface-induced bands are observed. A tentative explanation for the asymmetry between the A- and B-sides in terms of bonds on the ideal surface is proposed.