Cadmium stannate conductive layer with high optical transmittance and tunable work function

Abstract

200 nm cadmium stannate (Cd _2 SnO _4 ) transparent conductive layer films with a sheet resistance of 6.35 Ω/sq and resistivity of 1.27 × 10 ^−4 Ω · cm are deposited by magnetron sputtering coupling with adjustable target bias voltage followed by 620 °C 30 min annealing. The lowest resistivity of Cd _2 SnO _4 films reported before was 1.28 × 10 ^−4 Ω · cm, achieved with 510 nm Cd _2 SnO _4 . The average transmission rate of 200 nm sputtering Cd _2 SnO _4 films between 400–800 nm is 94%. The deposition rate increase target bias voltage can the and electrical performance of Cd _2 SnO _4 films. The surface work function of Cd _2 SnO _4 films is also tunable by target bias voltage. The Cd _2 SnO _4 phonon spectrum and phonon density of states combined with Raman microscope shows the Cd _2 SnO _4 films with most ideal electric properties has a identical phonon response. XPS shows the chemical component of as-deposited Cd _2 SnO _4 films and Cd _2 SnO _4 films after annealing with 120 V target bias voltage is Cd _2.03 SnO _6.36 and Cd _1.25 SnO _4.15 , respectively, which is contrary to the general conclusions that interstitial cadmium atoms and oxygen vacancies are the main self-doping defects in Cd _2 SnO _4 films.

Keywords

• cadmium stannate
• magnetron sputtering
• phonon density of states
• x-ray photoelectron spectroscopy