Investigation of D-TS effect on r.f. magnetron sputtered ZnO thin films

The aim of this study depends on understanding the effect of target-to-substrate distance (D-TS) on ZnO thin films deposited by r.f. magnetron sputtering on to glass substrates at room temperature conditions. The DTS was changed from 35 mm to 65 mm with steps of 5 mm at 165 W and 0.2 Pa. The deposition rate of the films were ranged from 76 angstrom / min to 146 angstrom / min, while 10(-3) Omega.cm was obtained as the resistivity value with the help of four point probe technique. The structural investigations were carried out by using both the x-ray diffraction (XRD) and high resolution transmission electron microscopy. According to XRD observations, the films were (002) oriented. Surface behaviour of the ZnO films was examined with atomic force microscopy and scanning electron microscopy. The root mean square (RMS) values were varied from 4.6 nm to 22.8 nm. Also, optical properties were obtained from UV-visible spectrophotometer and the transmittances as around 80%. At 45 mm DTS value, the minimum resistivity measured as 9 x 10(-4) Omega.cm with 76 angstrom / min deposition rate. The RMS was obtained as 4.9 nm and transmission was measured as 85.30 %, while band gap was 3.45 eV.