Figure 1

(Color online) Side view of the $\mathrm{Ti}{\mathrm{O}}_2$ rutile (110) surface along the row direction [001]. The large (blue) balls represent the Ti atoms, and the smaller (green) balls the O atoms. (a) The stoichiometric $(1\times 1)$ structure, (b) $(1\times 2)$ surface with missing ${\mathrm{O}}^{\mathrm{bri}}$ row, (c) reduced surface with all ${\mathrm{O}}^{\mathrm{bri}}$ rows removed, and (d) added-row $\left[\mathrm{ar}(1\times 2)\right]$ surface.Reuse & Permissions

Figure 2

A series of electron beam irradiated (at $60\mathrm{eV}$, and $1\mu \mathrm{A}$ emission) spots are imaged close to the MEM-LEEM transition. Spot diameter is $5\mu \mathrm{m}$. The lowest irradiation dose is $40\mathrm{s}$ and denoted by “l.” Each following spot was irradiated in $40\mathrm{s}$ increments. Spot “8” ($320\mathrm{s}$ irradiation) has the best $(1\times 2)$ reconstruction. The sample was oriented such that the spot displacement direction coincided with the $\left[1\overline{1}0\right]$ direction of the crystal.Reuse & Permissions

Figure 3

Intensity of the $(0,1∕2)$ LEED spot as a function of electron beam irradiation time at $60\mathrm{eV}$ electron energy. The LEED patterns were acquired at $60\mathrm{eV}$ during the irradiation. The optimum $(1\times 2)$ reconstruction was obtained at about $320\mathrm{s}$.Reuse & Permissions

Figure 4

The LEED $I\left(V\right)$ curves for two $\mathrm{Ti}{\mathrm{O}}_2$ surfaces showing $(1\times 2)$ reconstruction. The solid line marked as $\mathrm{LT}(1\times 2)$ is obtained by electron-stimulated desorption (ESD), whereas the dashed curve [$\mathrm{HT}(1\times 2)$ structure] belongs to the surface prepared by high temperature annealing.Reuse & Permissions

Figure 5

(a) $(1\times 1)$ LEED pattern of the $\mathrm{Ti}{\mathrm{O}}_2$ surface after a cleaning cycle, and (b) the resulting $(1\times 2)$ reconstruction after electron-stimulated desorption (ESD) at $60\mathrm{eV}$ electron energy and $320\mathrm{s}$ irradiation time. Both images were acquired at $31\mathrm{eV}$.Reuse & Permissions

Figure 6

(Color online) LEED profiles taken along the $\left[1\overline{1}0\right]$ direction as a function of electron beam irradiation time. The initial surface shows a $(1\times 1)$ structure with no trace of the half order peaks. The development of the $(1\times 2)$ reconstruction with increasing irradiation dose can be seen from the rise in $(0,1∕2)$ and $(0,3∕2)$ intensities. The decrease in the (0,0) intensity with irradiation time is shown in the inset.Reuse & Permissions

Figure 7

(Color online) Dependence of the LEED spot intensities and widths on the electron beam irradiation time for 1 ML Au deposition. (a) Intensities of the (0,0), (0,1), and $(0,3∕2)$ spots. (b) FWHM values of the same spots obtained from a fit to the peak shape along the [001] direction. The (0,1) and $(0,3∕2)$ peaks were fitted with a Lorentzian, whereas the (0,0) peak was a combination of Lorentzian and Gaussian as explained in the text. The figure shows the FWHM of the Gaussian contribution. The corresponding real space length scales are indicated on the right axis in Å. All LEED data are acquired at $31\mathrm{eV}$ electron energy.Reuse & Permissions

Figure 8

(Color online) Example fits to the peak shapes of the LEED spots for the $(1\times 2)$ surface. The three panels show the fits to the (a) (0,0), (b) (0,1), and (c) $(0,3∕2)$ spots. The profiles are taken along [001]. The LEED patterns are acquired at $31\mathrm{eV}$.Reuse & Permissions

Figure 9

(Color online) $\mathrm{Au}4f$ core level photoemission spectra of a 0.5 ML thick Au film from regions with different electron irradiation times (i.e., with different oxygen vacancy densities, e.g., 0.5 ML at $320\mathrm{s}$). The photon energy is $190\mathrm{eV}$.Reuse & Permissions

Figure 10

(Color online) Normalized peak area of the $\mathrm{Au}4f_{7∕2}$ core level photoemission spectra as a function of irradiation time for three different Au coverages on the $\mathrm{Ti}{\mathrm{O}}_2$ surface. The solid lines correspond to the fit as explained in Sec. 4. The dotted line marks the best $(1\times 2)$ structure.Reuse & Permissions

Figure 11

(Color online) $\mathrm{Au}4f$ core level spectra for the three Au coverages on the best $(1\times 2)$ surface (the dotted line in Fig. 10). In all the spectra, the high kinetic energy base line is normalized to unity and subtracted out.Reuse & Permissions

Figure 12

(a) Effect of the original electron beam irradiation and subsequent LEED measurement as seen by mirror electron microscopy (MEM). The field of view is about $30\mu \mathrm{m}$. The smaller circle inside each irradiated spot is due to the LEED measurement at $31\mathrm{eV}$ electron energy. (b) Again in MEM mode, one can see the effect of the photon beam used in the XPS measurements as a wide black stripe. The dark contrast is mainly due to photon beam induced reduction of the surface. (c) Effect of extended photon beam irradiation at room temperature on the $\mathrm{Au}4f$ signal, outside (squares) and inside (circles) a region electron beam irradiated for $320\mathrm{s}$. Au coverage is 1.0 ML. Note that, in the actual experiment, the XPS measurement times were limited to less than $4\min$ per region.Reuse & Permissions

Figure 13

(Color online) Top view of the $(1\times 2)$ surface unit cell (marked by dashed line) with labeling of the various initial Au adsorption sites (marked by squares): (a) missing row $(1\times 2)$ and (b) added row $(1\times 2)$. Large balls are Ti, and small balls are O atoms.Reuse & Permissions

Figure 14

(Color online) Side views of the final, optimized configurations of the monomer, dimer, and trimer Au rows adsorbed on the missing-row surface (left column) and the added-row reconstructed surface (right column). Large (blue), medium (red), and small (green) sized balls represent Ti, Au, and O atoms, respectively.Reuse & Permissions

Figure 15

(Color online) Electron density charge gain upon Au adsorption on the mr surface. Blue, green, and red balls represent Ti, O, and Au atoms, respectively. Isocharge surfaces in all graphs correspond to $0.03\text{electron}∕{\mathrm{\AA }}^3$. The configurations shown in columns (a)–(c) correspond to the monomer, dimer, and trimer Au rows displayed in Figs. 14a, 14b, 14c.Reuse & Permissions

Figure 16

(Color online) Electron density charge gain upon Au adsorption on the ar surface. Blue, green, and red balls represent Ti, O, and Au atoms, respectively. Isocharge surfaces in all graphs correspond to $0.01\text{electron}∕{\mathrm{\AA }}^3$. The structures shown in columns (a)–(c) correspond to the monomer, dimer, and trimer Au rows presented in Figs. 14d, 14e, 14f.Reuse & Permissions