Characteristics of low-resistivity aluminum-doped zinc oxide films deposited at room temperature by off-axis radio-frequency sputtering on flexible plastic substrates

The crystalline structure, morphology, composition, electrical transport, and optical properties of aluminum-doped zinc oxide (AZO) films are studied for applications in transparent electronics and optoelectronic devices. AZO thin films of c -axis-oriented growth and with different thickness were deposited on PET flexible plastic substrates at room temperature by rf magnetron sputtering. A larger grain size with a decreased strain ε value is observed in a thicker film, while changes in composition for films with different thicknesses are insignificant. Moreover, the resistivity of film decreases with increasing thickness, and the low-temperature electrical transport properties can be described by the scenario of quantum corrections to conductivity. With the room-temperature growth conditions, the resistivity of 4.5 × 10 −4 Ω cm, carrier concentration of 6.4 × 10 20 cm −3 , and transmittance of 80 % for the 1100-nm-thick film are obtained. In addition, the optical bandgap energy decreases with increasing film thickness, which can be attributed to the bandgap renormalization and crystallite size effects.