Improvement of the effective work function and transmittance of thick indium tin oxide/ultrathin ruthenium doped indium oxide bilayers as transparent conductive oxide

Abstract

Ruthenium doped indium oxide (In1−xRuxOy) films fabricated using DC magnetron co-sputtering with In2O3 and Ru targets were investigated for use as transparent conductive oxides. The In1−xRuxOy films had an amorphous structure in the wide compositional range of x=0.3–0.8 and had an extremely smooth surface. The transmittance and resistivity of the In1−xRuxOy films increased as the Ru content increased. The transmittance of the In0.38Ru0.62Oy film improved to over 80% when the film thickness was less than 5nm, while the specific resistivity (ρ) was kept to a low value of 1.6×10−4Ωcm. Based on these experimental data, we demonstrated that thick indium tin oxide (In0.9Sn0.1Oy, ITO) (150nm)/ultrathin In0.38Ru0.62Oy (3nm) bilayers have a high effective work function of 5.3eV, transmittance of 86%, and low ρ of 9.2×10−5Ωcm. This ITO/In0.38Ru0.62Oy bilayer is a candidate for use as an anode for organic electroluminescent devices.