Physical investigations on transparent conducting Mo:ZnO thin films

Molybdenum (Mo)-doped zinc oxide (ZnO) thin films were deposited by radio frequency (r.f.) magnetron sputtering on quartz and Si (100) substrates at two different substrate temperatures (473 and 673 K) and at a fixed combined partial pressure 5 Pa of Argon and O2. The atomic percentage (at.%) of (Mo) in ZnO was increased from 1 to 2 at.%. The results of X-ray diffraction revealed that the ZnO films deposited at 5 Pa at a substrate temperature of 473 K were highly c-axis oriented with a predominant (002) crystallographic orientation. The intensity of (002) decreased with an increase in the atomic percentage of Mo. Moreover, a growth in the (100), (101), (220), and (103) orientations was observed. The energy-dispersive spectrum (EDS) of the Mo:ZnO films deposited at 5 Pa and 473 K was substoichiometric, whereas the films deposited at 673 K were nearly stoichiometric. The surface morphology of the ZnO films is porous when deposited at 473 K. The optical energy gap of the ZnO films deposited at 473 K increased from 3.11 to 3.64 eV with an increase in the atomic percentage of Mo. The electrical resistivity of the ZnO films decreased from 1.7 × 10−4 to 6.7 × 10−5 Ωm with an increase in the substrate temperature and atomic percentage of Mo. The thickness of the films measured by spectroscopic ellipsometry is 440 nm.