Optical, electric and infrared emissing properties of DC magnetron sputtered ZnO:Al thin films

Aluminum-doped zinc oxide (ZnO: Al) films were deposited on glass substrate by DC reactive magnetron sputtering from a Zn-Al metallic target (ω(Al) = 3%). For the films with novel, tangly string-like surface morphology and an average optical transmittance up to 90% in the visible range, a widest band gap of 3.47 eV and electric resistivity down to 1.80 × 10^-6 Ω·m were obtained. The infrared emissivity in 8-14 μm waveband is distributed in the range of 0.26-0.9. The surface morphology, crystallinity and infrared emissivity as well as the optical and electric properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, spectrophotometry, infrared radiometer and Hall-effect measurement. The optical, electric and infrared emitting properties of the films depend on substrate temperature and sputtering power obviously and regularly. The relationship between sheet resistance and infrared emissivity of ZnO:Al(ZAO) thin films follows a quadratic function when the sheet resistance is below 45 Ω.