CuInO2 Thin Films Research Articles

Optical Studies of RF Sputtered CuInO2 Thin Films

N type transparent conducting oxide semiconductors have been researched extensively in the past. P-type transparent semiconductors have been comparatively researched lesser. In order to advance in the field of transparent p-n junction devices, more and more researches are being done on p-type transparent semiconductors. CuInO2 is one of the p-type transparent semiconductor that has the prospects of being used extensively in transparent p-n junction devices. CuInO2 (50:50 of Cu2O: In2O3) thin films were RF sputter deposited onto glass slides. Optical transmission studies were performed on these thin films to extract the band gap. The deposition studies were also performed. The sputtered films were subsequently post annealed in different temperatures and different ambient conditions and their respective optical transmissions were recorded.

Tin-incorporated nanostructured copper indium oxide delafossite thin films: Structural, electrical and optical analysis

Single phase polycrystalline Sn-doped CuInO2 thin films are prepared by the oxygen plasma enhanced reactive evaporation method. X-ray diffraction indicates a preferential orientation of crystallites along the (006) plane on doping while energy dispersive analysis of X-rays and atomic force microscopy are employed to appraise the composition and morphology of the films, respectively. Remarkably, about 2-3 orders of magnitude enhancement in their electrical conductivity than that reported till date is observed. Further, the Sn-doped thin films possess 2-3 orders of magnitude higher carrier concentration (1018-1019/cm3) than undoped films that is associated with a drastic reduction in mobility. Moreover, different conduction mechanisms possible at different temperature regions ranging from around 55 K–450 K are studied in detail. While the transparency of the films is increased from 43% to 85% on doping, the optical band gap decreases from 3.83 eV to 3.5 eV.

Correlation Between Crystallite Orientation and Electrical Conductivity in Delafossite CuInO2 Thin Films: Effect of Low Energy Ion Irradiation

Correlation Between Crystallite Orientation and Electrical Conductivity in Delafossite CuInO₂ Thin Films: Effect of Low Energy Ion Irradiation

Electrical and optical properties of Sn doped CuInO2 thin films: Conducting atomic force microscopy and spectroscopic ellipsometry studies

Tin doped CuInO2 thin films deposited by rf magnetron sputtering technique show columnar structure with (006) preferred orientation. Conducting atomic force microscopy measurements show the presence of nanoconductivity regions when the current flow direction is along the in-plane InO6 layer and absence of conducting regions when the current direction is along O–Cu–O layers perpendicular to the film surface. The strong anisotropy observed in the electrical properties of tin doped samples is due to the preferred crystallite orientation and highly anisotropic delafossite structure. A large change in the electrical conductivity value and activation energy value in undoped films and tin doped samples has also been explained in terms of change in crystallite orientation on doping. Spectroscopic ellipsometry measurements have been used to determine the optical constant and dielectric function of CuInO2 and CuInO2:Sn films and show a band gap value of 4.5 eV in tin doped samples due to removal of structural defects.

Effect of structural anisotropy on electronic conduction in delafossite tin doped copper indium oxide thin films

Sn doped CuInO2 thin films having a single delafossite phase have been synthesized by magnetron sputtering technique. A gradual decrease in the activation energy from 0.43 to about 0.10 eV and a large increase in conductivity are observed in Sn doped samples with increasing fraction of crystallites having (006) orientation due to an increase in substrate temperature. Due to thermally activated carrier transport along O-A-O layers and activated carrier generation along BO6 layers, crystallite orientation becomes a crucial factor in controlling the conduction in delafossite thin films.

Structural, optical and electrical properties of transparent conducting CuInO2 thin films prepared by RF sputtering

AbstractThe transparent conducting CuInO2 thin films were prepared by radio frequency (RF) reactive sputtering and post growth annealing. A study of structural, optical, and electrical properties was performed on the films. The crystalline phase in the films was identified to be the delafossite structure. The optical properties, such as the wavelength dependence of the transmittance and the band gap energy, were determined. The average transmittance is 70% in the wavelength range of 400-1100 nm and the band gap is ˜3.7 eV. The temperaturedependence of electrical conductivity in the CuInO2 delafossite thin films was measured from 70 to 400K. The resistivity, carrier density, and mobility of the thin films at 300K were 1.8x101 Δcm, 1.6x1019 cm-3 and 2x10-1 cm2/Vs, respectively. Hall coefficient indicated that the CuInO2 thin films are n-type conductors. The electrical conductivity showed semiconducting type at room temperature.

A simple method for the preparation of transparent p-type Ca-doped CuInO2 films: Pulsed-laser deposition from air-sintered Ca-doped Cu2In2O5 targets

We report the deposition of single-phase undoped and Ca-doped CuInO2 thin films from a readily synthesized source target of Cu2In2O5—circumventing the very difficult fabrication of CuInO2 targets. X-ray diffraction shows that single-phase materials were obtained over a range of substrate temperatures and deposition pressures. p-type conductivities are measured to be ∼3×10−3S∕cm, comparable to the best films previously reported. The optical properties of the films were measured by spectroscopic ellipsometry.

Bipolarity in electrical conduction of transparent oxide semiconductor CuInO2 with delafossite structure

A transparent oxide semiconductor with delafossite structure, CuInO2, was found to exhibit both p-type and n-type conduction by doping of an appropriate impurity and tuning of proper film-deposition conditions. Thin films of Ca-doped or Sn-doped CuInO2 (optical band gap=∼3.9 eV) were prepared on α-Al2O3(001) single crystal substrates by pulsed laser deposition method. The films were deposited at 723 K in O2 atmosphere of 1.0 Pa for the Ca-doped films or 1.5 Pa for the Sn-doped films. The positive sign of the Seebeck coefficient demonstrated p-type conduction in the Ca-doped films, while the Seebeck coefficient of the Sn-doped films was negative indicating n-type conductivity. The electrical conductivities of Ca-doped and Sn-doped CuInO2 thin films were 2.8×10−3 S cm−1 and 3.8×10−3 S cm−1, respectively, at 300 K.

Bipolar Electrical Conductive Transparent Oxide, CuInO2

ABSTRACTA transparent oxide semiconductor with delafossite structure, CuInO2, was found to exhibit both p-type and n-type conduction by doping of an appropriate impurity and tuning of proper film-deposition conditions. Thin films of Ca-doped or Sn-doped CuInO2 were prepared on -Al2O3 (001) single crystal substrates by pulsed laser deposition method. The films were deposited at 723 K in O2 atmosphere of 1.0 Pa for the Ca-doped films or 1.5 Pa for the Sn-doped films. The positive sign of the Seebeck coefficient demonstrated p-type conduction in the Ca-doped films, while the Seebeck coefficient of the Sn-doped films was negative indicating n-type conductivity. The electrical conductivities of Ca-doped and Sn-doped CuInO2 thin films were 2.8×10−3 S·cm−1 and 3.8×10−3 S·cm−1, respectively, at 300 K. The optical band gap of each film was estimated to be ∼3.9 eV. Since CuInO2 exhibited bipolarity in electrical conduction, transparent p-n homojunctions based on CuInO2 were fabricated on (111) surface of yttria-stabilized zirconia single-crystal substrates. The structure of the diode was In2O3:Sn / n-CuInO2:Sn / p-CuInO2:Ca / In2O3:Sn electrode on the substrate. The contact between the n-and p-type CuInO2 semiconducting oxides was found to be rectifying. The turn-on voltage was ∼1.8 V.