Highly conductive and transparent aluminum-doped zinc oxide thin films deposited on polyethylene terephthalate substrates by pulsed laser deposition

Abstract

Highly transparent and conductive aluminum-doped zinc oxide thin films were deposited on low-cost flexible polyethylene terephthalate substrates at room temperature using pulsed laser deposition and the effects of oxygen pressure and film thickness on film properties were investigated. It was found that grain sizes play a greater role only at smaller film thicknesses in affecting carrier mobility. Resistivity changes at larger film thickness can be caused by near surface/interface depletion that affected both mobility and carrier concentration. The inherent film transparency did not change and any reduction in the film transmittance is likely related to a thickness dependent attenuation effect. This means that different transparent conducting oxides should each possess an optimum film thickness, whereby optimized zinc oxide is typically about 100nm. A low resistivity of ~6.6×10−4Ωcm with a high normalized transparency index of >0.9 for a 110±10nm thick room-temperature deposited film was obtained, representing one of the best results obtained to date.