A photoemission investigation of the adsorption of potassium on perfect and defective TiO2(110) surfaces

Interaction of nanostructured metal overlayers with oxide surfaces

“…This was observed by Lad and Dake [342] where they reported that K 2 O multilayers, more than 9 monolayers thick, grew at 300 K by extracting oxygen from the TiO 2 bulk to the surface. The K 2 O layers are stable against annealing at 900 K. Similar K-adsorptioninduced O diffusion to the surface was reported by Heise et al [282]. For the Ca/TiO 2 interface, XPS data showed that 3 nm thick Ca overlayers were oxidized during depositing Ca on TiO 2 surfaces [283].…”

“…This electronic interaction can be observed by XPS measurements, where shoulder peaks at low BE in XPS Ti2p spectra appear due to the electron transfer from metal to surface Ti. The results have been found in many metal/TiO 2 interfaces [281][282][283][284][285][286].…”

Alkali-Metals on ZnO(10-10) Studied by Low-Energy Electron Diffraction and Photoelectron Spectroscopy

“…1b and 4 Zn species are not formed on ZnO(1010) even though both Na and Cs are ionized and valence charge is transferred to the substrate. Such an observation is in sharp contrast to the results of the PES experiments for other AM/oxide systems such as K/TiO 2 (110) [31], Na/TiO 2 (110) [32] and Na/Fe 3 O 4 (111) [33], where the reduced metal species are observed as a shoulder structure at the lower bindingenergy side of the main peak in the core-level spectra. For TiO 2 and Fe 3 O 4 , the metal d orbitals contribute to the lower part of the conduction bands, and thus transferred charge should occupy the metal d orbital.…”

The defined adsorption site of sodium on the TiO2(110)–(1×1) surface

“…6). Indeed, the strong increase of the A=B ratio between the two components of the Ti LMV Auger peak upon sodium coverage is indicative of an increase of the Ti 3þ /Ti 4þ ratio at the vicinity of the surface [20], or, in other words, of the charge transfer from the alkali metals adatoms to the titanium ions [1,2,9].…”

“…Despite this practical interest, studies in the field are scarce, except several papers dealing with alkali metals on rutile [1,2,[5][6][7][8][9][10][11][12][13][14]. At low coverage, the work function change and the occurrence of reduced Ti 3þ [1,2,9] are indicative of an ionic adsorption of alkali metal on TiO 2 (1 1 0). At higher coverages, the charge transfer per alkali metal adatom decreases, but slower than on metal and semiconductor surfaces [1,2,5].…”