Effect of Enhanced Plasma Density on the Properties of Aluminium Doped Zinc Oxide Thin Films Produced by DC Magnetron Sputtering

Aluminum doped zinc oxide (AZO) thin films were prepared by DC magnetron sputtering at low substrate temperature. A coaxial solenoid coil was placed near the magnetron target to enhance the plasma density (Ji). The enhanced plasma density improved significantly the bulk resistivity (ρ) and its homogeneity in spatial distribution of AZO films. X-ray diffraction (XRD) analysis revealed that the increased Ji had inuenced the crystallinity, stress relaxation and other material properties. The AZO films deposited in low plasma density (LPD) mode showed marked variation in ρ (ranging from ～6.5×10?2 to 1.9×10-3 ·cm), whereas those deposited in high plasma density (HPD) mode showed a better homogeneity of films resistivity (ranging from ～1.3×10?3 to 3.3×10?3 ?·cm) at di?erent substrate positions. The average visible transmittance in the wavelength range of 500–800 nm was over 80%, irrespective of the deposition conditions. The atomic force microscopy (AFM) surface morphology showed that AZO films deposited in HPD mode were smoother than that in LPD mode. The high plasma density produced by the coaxial solenoid coil improved the electrical property, surface morphology and the homogeneity in spatial distribution of AZO films deposited at low substrate temperature.