Post-annealed aluminum-doped zinc oxide/tin-doped indium oxide bilayer films for low emissivity glass

Abstract

This study uses post-annealed aluminum-doped zinc oxide /tin-doped indium oxide bilayer (AZO/ITO) films for low emissivity glass. The AZO/ITO films are deposited on glass substrates using in-line sputtering. The AZO/ITO films are subjected to either vacuum or hydrogen plasma annealing. The microstructure, the visible transmittance, the electrical properties and the emissivity of as-deposited, vacuum-annealed and plasma-annealed AZO/ITO films are measured. Hydrogen plasma annealing changes the surface morphology of AZO/ITO films. The average visible transmittance increases and the electrical resistivity and emissivity decrease for AZO/ITO films after vacuum or plasma annealing. The vertical cross-section and surface morphology for vacuum-annealed AZO/ITO films is similar to that for as-deposited films. The surface roughness of AZO/ITO films increases and polygonal grains form after plasma annealing. The electrical resistivity of the vacuum-annealed and hydrogen plasma-annealed AZO/ITO films is 59% and 63% less than the value for as-deposited films. The average visible transmittance of the vacuum-annealed and hydrogen plasma-annealed AZO/ITO films is 8.64% and 12.71% greater than the value for as-deposited films. The emissivity of vacuum-annealed and hydrogen plasma-annealed samples is 2.3 times and 2.56 times less than that of as-deposited AZO/ITO films. The emissivity and the average visible transmittance for vacuum-annealed and hydrogen plasma-annealed AZO/ITO films is 0.09 and 81.58% respectively, which is within the range for commercial low emissivity materials.