The n-type conduction of indium-doped Cu2O thin films fabricated by direct current magnetron co-sputtering

Abstract

Indium-doped Cu2O thin films were fabricated on K9 glass substrates by direct current magnetron co-sputtering in an atmosphere of Ar and O2. Metallic copper and indium disks were used as the targets. X-ray diffraction showed that the diffraction peaks could only be indexed to simple cubic Cu2O, with no other phases detected. Indium atoms exist as In3+ in Cu2O. Ultraviolet-visible spectroscopy showed that the transmittance of the samples was relatively high and that indium doping increased the optical band gaps. The Hall effect measurement showed that the samples were n-type semiconductors at room temperature. The Seebeck effect test showed that the films were n-type semiconductors near or over room temperature (<400 K), changing to p-type at relatively high temperatures. The conduction by the samples in the temperature range of the n-type was due to thermal band conduction and the donor energy level was estimated to be 620.2–713.8 meV below the conduction band. The theoretical calculation showed that indium doping can raise the Fermi energy level of Cu2O and, therefore, lead to n-type conduction.

Effects of Oxygen Flow Rates on the Physical Characteristics of Magnetron Sputtered Single-Phase Polycrystalline Cu2O Films

“…The E g corresponded to the sample A, B, C and D were about 2.30, 1.88, 1.69 and 1.66 eV respectively, which presented a decreasing trend with the increasing of the oxygen flow rates. According to the curve of sample A, the E g of the single-phase Cu 2 O film was 2.30 eV, which was in good agreement with the reported value of RF magnetron sputtered Cu 2 O films 34 . The decreasing value of E g was due to the generation of CuO phase, this phenomenon was similar with Alkoy and Prabu's research work 38,39 .…”

Functional Oxides for Photoneuromorphic Engineering: Toward a Solar Brain

“…The donor microscopic origin remains unclear with O vacancies, Cu interstitials, inversion layers or extrinsic defects as possible candidates [244] . Due to a self-compensation effect and their reduced dopant solubility, only very few extrinsic impurity atoms have shown a sizable degree of donor doping [245] , [246] . A Cu 2 O p-n homojunction is therefore still challenging (i.e., small grains and poor n-type activation) [247] , [248] , [249] although it is technologically very relevant for optoelectronics owing its low electron affinity [56] .…”

Enhancement of Nonlinear Optical and Dielectric Properties of Cu2O Films Sandwiched with Indium Slabs

“…[23] The doping of Cu 2 O with indium resulted in maximum Hall mobility and free carrier density of 7.59 cm 2 V À1 s À1 and 9.9 Â 10 14 cm À3 . [23] In contrast to our observation, the energy bandgap of Cu 2 O increased upon indium doping. [23] The behavior of the indium-doped samples was ascribed to the In 2 O 3 alloy formation mechanism in Cu 2 O films.…”

“…It is also worth comparing the effect of the indium slab insertion between two layers of Cu 2 O with the indium-doped Cu 2 O. [23] The doping of Cu 2 O with indium resulted in maximum Hall mobility and free carrier density of 7.59 cm 2 V À1 s À1 and 9.9 Â 10 14 cm À3 . [23] In contrast to our observation, the energy bandgap of Cu 2 O increased upon indium doping.…”