Effects of thickness on 1/f noise of Co and In co-doped ZnO

We have investigated the effects of thickness on the electrical properties of Co
_2%
and In
_1%
co-doped ZnO films (CIZO) grown on glass substrates at room temperature by Radio Frequency (RF) magnetron sputtering technique. The sheet resistance R
_sh
[Ω], the resistivity ρ [Ω.cm], and the 1/f noise have been analysed as a function of thickness from 50 nm to 450 nm. The electrical properties and 1/f fluctuation noise were carried out by using four-point probe method. In order to reduce the contacts problems, we applied a constant current through the pair of inner electrodes and observed the voltage fluctuations across the pair of outer electrodes. We characterized the noise below 100 kHz and obtained classical 1/f spectra. We attempted to verify the validity of Hooge's empirical relation and to test its usefulness as a diagnostic tool. The results show that the noise coefficient K [cm
²
/03A9] = C
_us
/ R
_sh
increases with the thickness twhich indicates that mobility and the noise parameter α
_H
shrinks with a shrinking thickness. We have also studied the structural and optical properties of these films.