Electrical and optical properties of Al:ZnO films prepared by ion-beam assisted sputtering

Al-doped ZnO (AZO) thin film is an important transparent and conducting electrode in optoelectronic devices. Further reduction of the resistivity and an increase in the transmittance of AZO are required. This paper proposes AZO films that are prepared using ion-beam assisted sputtering (IBAS). A low-energy Ar ion-beam with a kinetic energy between 0 and 50 eV is used. The electrical and optical properties of IBAS AZO films are studied in terms of the substrate temperature (RT-300 °C). The results show that the resistivity of AZO films decreases as the amount of chemisorbed oxygen and O–Zn bonds decrease, which increases the number of oxygen vacancies. The transmittance in the visible region is increased because of the high crystallinity of AZO films. The resistivity of IBAS AZO deposited at 300 °C with an anode voltage of 30 V is reduced to 5.6×10−3 Ω cm because of the high carrier concentration and mobility. This shows that that ion-beam treatment changes the surface/adatom reaction during the growth of AZO films, which is similar to the effect of substrate heating. The electrical and optical properties of the AZO films that depend on the ion-beam energy and substrate temperature are discussed.