THE ROLE OF THICKNESS ON THE STRUCTURAL AND ELECTRICAL PROPERTIES OF DC MAGNETRON SPUTTERED NANO ZNO THIN FILMS

The objective of this research is investigating the effect of the thickness on the structural and electrical properties for nano ZnO thin films prepared by d.c magnetron sputtering on glass substrates. The deposition parameters such as power, target to-substrate spacing, substrate temperature and sputtering gas composition, self-heating of the substrate in plasma during film deposition were investigated. Thicknesses (t) of nanoZnO thin films are altered by varying the deposition time from 45 min to 90 min (t=50,100,150 and 200 nm) and was determined using optical method. Crystal structure were investigated by mean of a X-ray diffraction (XRD), it was found that all the films have peak located at 2θ ≈ 34.4o with hkl (002), in addition there were another peaks appear at thickness 100 nm, 150 nm and 200 nm.The crystalline was increased with increasing (t). The grain size increased from 9.462 nm to 11.8522 nm as the film thickness increased from 50 to 200nm. General observations indicate that microstructure parameters, such as grain size, depend sensitively on the exact nature of the deposition conditions. The d.c conductivity (σ) for nano ZnO thin films has been studied as a function of thicknesses. From all samples we can be noticed that the resistivity (ρ) increased with increasing the temperature and film thickness, while the activation energies decreased. The carrier concentration and mobility have been studied