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摘要
A group of aluminum-doped zinc-oxide (AZO) films were prepared on glass substrates by direct-current reactive magnetron sputtering at substrate temperatures (T(s)) ranging from 170 degrees C to 210 degrees C. The optical constants of the AZO films defined by using Caughy model were fitted in terms of a two-layer model by using the measured spectroscopic ellipsometric parameters. The refractive index dispersion data below the interband absorption edge of the AZO films were analyzed by using a single-oscillator model. The optical energy gap as-fitted by using the single-oscillator model demonstrated a blue and a red shift as T(s) increased from 170 degrees C to 200 degrees C and above 200 degrees C, respectively. This could be attributed to a change in the free electron concentration, which was related to a change in the effective Al-doping efficiency. The calculated parameter beta, related to the crystalline structure, indicated that the as-deposited AZO films fell into an ionic class even though beta had a slight deviation from the ionic value. The beta of the as-deposited AZO film at 200 degrees C largely remained in the range of ionic values, indicating a minimum deviation from the wurtzite structure. This denoted that Al is a very effective substitute for the zinc sites. Additionally, the calculated plasma frequency, (h) over bar omega(p), remained in the violet region.
