Thin films of β-Ga2O3 with an energy band gap of 4.9 eV were prepared on silica glass substrates by a pulsed-laser deposition method. N-type conductivity up to ∼1 S cm−1 was obtained by Sn-ion doping and deposition under low O2 partial pressure (∼10−5 Pa) at substrate temperatures above 800 °C. The resulting internal transmittance at the wavelength (248 nm) of the KrF excimer laser exceeded 50% for the 100-nm-thick film, making this the most ultraviolet-transparent conductive oxide thin film to date and opening up prospects for applications such as ultraviolet transparent antistatic electric films in ultraviolet lithography.

Transparent p-type conducting CuGaO2 thin films were prepared on α-Al2O3 (001) single-crystal substrates by pulsed laser deposition. The films were grown epitaxially on the substrates in an as-deposited state. X-ray pole figure analysis revealed that the films were composed of two types of epitaxial grains, both with c axes oriented perpendicular to the surface and a axes rotated 60° with respect to each other around the c axis. Observation of the CuGaO2 thin films by atomic force microscopy and high-resolution transmission electron microscopy substantiated this conclusion. The films have high optical transparency (∼80%) in the visible region, and the energy gap of CuGaO2 for direct allowed transition was estimated to be 3.6 eV. p-type conductivity was confirmed by Seebeck and Hall measurements. The electrical conductivity, carrier (positive hole) density, and Hall mobility of the films at room temperature were 6.3×10−2 S cm−1, 1.7×1018 cm−3, and 0.23 cm2 V−1 s−1, respectively.

An ultraviolet light-emitting diode (LED) operating at room temperature was realized using a p–n heterojunction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Multilayered films prepared by a pulsed-laser deposition technique were processed by conventional photolithography with the aid of reactive ion etching to fabricate the LED device. A rather sharp emission band centered at 382 nm was generated when a forward bias voltage exceeding the turn-on voltage of 3 V was applied to the junction. The emission may be attributed to a transition associated with the electron–hole plasma of ZnO.

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Highly electrically conductive indium–tin–oxide thin films were epitaxially grown on an extremely flat (100) surface of yttria-stabilized zirconia single-crystal substrates at a substrate temperature of 600 °C by a pulsed-laser deposition technique. A resistivity down to 7.7×10−5 Ω cm was reproducibly obtained, maintaining optical transmission exceeding 85% at wavelengths from 340 to 780 nm. The carrier densities of the films were enhanced up to 1.9×1021 cm−3, while the Hall mobility showed a slight, almost linear, decrease from 55 to 40 cm2 V−1 s−1 with increasing SnO2 concentration. The low resistivity is most likely the result of the good crystal quality of the films.