Transport and angular resolved photoemission measurements of the electronic properties of In2O3 bulk single crystals
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(a) CVT grown In2O3 single crystals. (b) Laue diffraction pattern of an In2O3 crystal. The three-fold symmetry of the  orientation of the cubic-space-centred lattice can be observed clearly. We have identified the spots 112, 121, and 211 and also all six crystallographic directions corresponding to the ΓN direction (for instance [−101] and commutations under reference to the Laue Atlas.13 (c) Temperature dependent resistivity curve of the In2O3 crystals. With increasing temperature from 2 K the resistivity decreases until a minimum at T = 219 K is reached and increases then to a room temperature value of 8.5 mΩ·cm. (d) Temperature dependent Hall coefficient, negative for the whole temperature range. This means that the crystals have n-type conductivity. (e) The temperature dependent mobility has a maximum at about 200 K. The room temperature value is 66 cm2/V·s. (f) Charge carrier density with a maximum at about T = 30 K and a minimum at about 150 K, which occurs at about 0.01 K−1 on the reciprocal temperature scale.
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(a) ARPES spectra series of an In2O3 single crystal taken at normal emission with photon energies from 17 eV to 25 eV. The tick marks show the obtained peak positions from a fit with four Gaussians shown in detail in (b). (b) ARPES spectrum of In2O3 at 18 eV photon energy showing the valence band and the conduction band minimum at the Γ point. Included is a global fit to the valence bands and the conduction band. The conduction band has a 25 times lower intensity as the maximum of valence bands. The energy distance Eg1 between the uppermost valence band at 3.0 eV binding energy and the conduction band is the fundamental bandgap of In2O3. (c) Dispersion of the conduction band (red solid line), the flank of the conduction band (red dashed line) and the flank of the uppermost valence band (red dashed line) in k ⊥ (ΓP direction) taken at 18 eV photon energy. In a first step the spectra were fitted by Gaussians. The obtained energy positions were then connected by a parabola fit (red drawn line). The dashed red lines represent parabola fits of the inflection points of tangents drawn at the flank of the VB and the CB, respectively. (d) Dispersion of the conduction band (blue solid line), the flank of the conduction band (blue dashed line) and the flank of the uppermost valence band (blue dashed line) in k || (ΓP direction) taken at 18 eV photon energy. In a first step, the spectra were fitted by Gaussians. The obtained energy positions were then connected by a parabola fit (blue drawn line). The dashed blue lines represent parabola fits of the inflection points of tangents drawn at the flank of the VB and the CB, respectively. Parabola fits through the dispersions of the conduction band (e) and the flank of the uppermost valence band (f). The parabola fits facilitate the determination of effective masses.
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(a) Sketch of the Brillouin zone of the bcc crystal structure representative for In2O3. Marked are the ΓP 〈111〉 direction (blue arrow) and the orthogonal ΓN plane (blue area). (b) Top view of the ΓN plane with a sketch of the Fermi surface of the conduction band in yellow. The sample was orientated in a way that one of the symmetry directions (ΓN) was parallel to the electrical field vector E of the incident synchrotron light. (c) Experimental Fermi surface due to the conduction band minimum of In2O3. The dispersion in k-parallel direction was performed at the same photon energy (18 eV) as for the Γ point of the valence band maximum. An energy interval of 20 meV at the Fermi edge was integrated and plotted in a so called Fermi-map.
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