[Zurück]

D. Hagleitner, M. Menhart, P. Jacobson, S. Blomberg, K. Schulte, E. Lundgren, M. Kubicek, J. Fleig, F. Kubel, C. Puls, A. Limbeck, H. Hutter, L. Boatner, M. Schmid, U. Diebold:
"Bulk and surface characterization of In₂O₃(001) single crystals";
Physical Review B, 85 (2012), S. 1154411 - 11544111.

A comprehensive bulk and surface investigation of high-quality In2O3(001) single crystals is reported.
The transparent-yellow, cube-shaped single crystals were grown using the flux method. Inductively coupled
plasma mass spectrometry (ICP-MS) reveals small residues of Pb, Mg, and Pt in the crystals. Four-point-probe
measurements show a resistivity of 2.0 ± 0.5 × 105 ! cm, which translates into a carrier concentration of
"1012 cm−3. The results from x-ray diffraction (XRD) measurements revise the lattice constant to 10.1150(5) °A
from the previously accepted value of 10.117 A° . Scanning tunneling microscopy (STM) images of a reduced
(sputtered/annealed) and oxidized (exposure to atomic oxygen at 300 $C) surface show a step height of 5 A° ,
which indicates a preference for one type of surface termination. The surfaces stay flat without any evidence for
macroscopic faceting under any of these preparation conditions. A combination of low-energy ion scattering
(LEIS) and atomically resolved STM indicates an indium-terminated surface with small islands of 2.5 °A
height under reducing conditions, with a surface structure corresponding to a strongly distorted indium lattice.
Scanning tunneling spectroscopy (STS) reveals a pronounced surface state at the Fermi level (EF). Photoelectron
spectroscopy (PES) shows additional, deep-lying band gap states, which can be removed by exposure of the
surface to atomic oxygen. Oxidation also results in a shoulder at the O 1s core level at a higher binding energy,
possibly indicative of a surface peroxide species. A downward band bending of 0.4 eV is observed for the reduced
surface, while the band bending of the oxidized surface is of the order of 0.1 eV or less.