Substrate Bias Influenced Physical Characteristics of Nanocrystalline Silver Copper Oxide Films

Abstract

The silver-copper-oxide (Ag₂Cu₂O₃) films were prepared by reactive magnetron sputtering of equimolar silver copper alloy target (Ag₅₀Cu₅₀) onto the glass substrates in an oxygen partial pressure of 2 × 10⁻² Pa and at different substrate bias voltages in the range from 0 to −90 V. The X-ray photoelectron spectroscopic studies on the films formed at substrate bias voltage of −60 V showed the characteristic core level binding energies of Ag₂Cu₂O₃. The films formed on unbiased substrates were X-ray amorphous. The mixed phase films of Ag₂Cu₂O₃ and Ag were deposited at substrate bias voltage of −30 V, where as nanocrystalline and single phase Ag₂Cu₂O₃ films were achieved at substrate bias voltage of −60 V. The atomic force micrographs of the unbiased films showed spherical shaped grains while those deposited at higher substrate bias voltages exhibited grains with pyramidal shape. The electrical resistivity of the films increased from 1.2 × 10⁻⁵ to 8.6 × 10⁻³ Ωcm with increase of substrate bias voltage from 0 to −60 V respectively. The optical band gap of the films increased from 1.78 to 1.92 eV with increase of substrate bias voltage from 0 to −60 V.