Suppression of contact noise in a study on 1/f noise as a function of film thickness in Al-doped ZnO

Aluminum doped-zinc oxide (AZO) thin films were prepared on glass substrate by radio-frequency (RF) sputtering at room temperature. The sheet resistance, Rsh [Ω] the resistivity, ρ [Ω·cm] and the 1/f noise were studied as a function of thickness, t from 50 nm to 450 nm. The eddy current characterized the homogeneity of AZO thin films. The surface morphology has been analysed by atomic force microscopy (AFM). The 1/f noise is normalized with respect to the bias, frequency and unit area, and Cus is proportional to the sheet resistance Rsh. Two configurations were used to characterize material and contact noise. The pressure effect of four point-probe on the material and the contact noise were also investigated. Our results show that the homogeneity of the samples increases as the film thickness increases and the resistivity decreases with increasing thickness and reaches the lowest value of 1 × 10− 3 Ω cm at 450 nm. The average grain size and the root-mean-square roughness increases with rising thickness. The ratio K = Cus / Rsh is proportional to t2, which indicates that the mobility and the noise parameter αH shrink with the shrinkage of the thickness.