Characteristics of transparent conducting Al-doped ZnO films prepared by dc magnetron sputtering

Al-doped ZnO (AZO) films were deposited on soda-lime glass substrates by using dc magnetron sputtering as a function of argon gas pressure, O2/Ar gas ratio and substrate temperature, and their electrical and optical properties were investigated. As a result, the resistivity of the AZO films decreased with decreasing argon gas pressure or O2/Ar gas ratio. However, the lowest resistivity could be obtained at the substrate temperatures of 250 °C. The higher substrate temperature increased the resistivity a little. The transmittance was found to be very sensitive to O2/Ar gas ratio and substrate temperature. Addition of a very small amount of oxygen to argon (1.23% of O2/Ar ratio) or slight increase of the substrate temperature from room temperature to 150 °C enhanced the transmittance in visible region remarkably. Conclusively, the AZO films with low resistivity of order of 10−4 Ω cm and high transparency in visible region could be prepared at the substrate temperatures of above 150 °C (the lowest resistivity of 3.19 × 10−4 Ω cm at 250 °C) by dc magnetron sputtering and these films are applicable to various fields which require transparent conducting oxide films.