Fabrication of P-type Transparent Oxide Semiconductor SrCu2O2 Thin Films by RF Magnetron Sputtering

Abstract

Most TCOs such as ITO, AZO(Al-doped ZnO), FTO(F-doped <TEX>$SnO_2$</TEX>) etc., which have been widely used in LCD, touch panel, solar cell, and organic LEDs etc. as transparent electrode material reveal n-type conductivity. But in order to realize transparent circuit, transparent p-n junction, and introduction of transparent p-type materials are prerequisite. Additional prerequisite condition is optical transparency in visible spectral region. Oxide based materials usually have a wide optical bandgap more than ~3.0 eV. In this study, single-phase transparent semiconductor of <TEX>$SrCu_2O_2$</TEX>, which shows p-type conductivity, have been synthesized by 2-step solid state reaction at <TEX>$950^{\circ}C$</TEX> under <TEX>$N_2$</TEX> atmosphere, and single-phase <TEX>$SrCu_2O_2$</TEX> thin films of p-type TCOs have been deposited by RF magnetron sputtering on alkali-free glass substrate from single-phase target at <TEX>$500^{\circ}C$</TEX>, 1% <TEX>$H_2$</TEX>/(Ar + <TEX>$H_2$</TEX>) atmosphere. 3% <TEX>$H_2$</TEX>/(Ar + <TEX>$H_2$</TEX>) resulted in formation of second phases. Hall measurements confirmed the p-type nature of the fabricated <TEX>$SrCu_2O_2$</TEX> thin films. The electrical conductivity, mobility of carrier and carrier density <TEX>$5.27{\times}10^{-2}S/cm$</TEX>, <TEX>$2.2cm^2$</TEX>/Vs, <TEX>$1.53{\times}10^{17}/cm^3$</TEX> a room temperature, respectively. Transmittance and optical band-gap of the <TEX>$SrCu_2O_2$</TEX> thin films revealed 62% at 550 nm and 3.28 eV. The electrical and optical properties of the obtained <TEX>$SrCu_2O_2$</TEX> thin films deposited by RF magnetron sputtering were compared with those deposited by PLD and e-beam.