Transparent thin films of pure and nickel-doped ZrO2 are grown successfully by sol-gel dip-coating technique. The structural and optical properties according to the different annealing temperatures (300 oC, 400 oC and 500 oC) are investigated. Analysis of crystallographic properties through X-ray diffraction pattern reveals an increase in crystallite size due to increase in crystallinity with temperature. All fabricated thin films are highly-oriented along (101) planes, which enhances the increase in nickel doping. Scanning electron microscopy and energy dispersive spectroscopy are employed to confirm the homogeneity in surface morphology as well as the doping configuration of films. The extinction coefficient is found to be on the order of 102, showing the surface smoothness of deposited thin films. UV-visible spectroscopy reveals a decrease in the optical band gap with the increase in annealing temperature due to the increase in crystallite size. The variation in Urbach energy and defect density with doping and the change in annealing temperature are also studied.

Abstract
1. Introduction
2. Experimental Procedure
3. Results and Discussion
    3.1. Morphological and Elemental Analysis
    3.2. Structural Analysis
    3.3. Optical Analysis
4. Conclusions
References

• Davinder Kumar(Department of Physics, Punjabi University, Patiala, Punjab 147002, India)
• Avtar Singh(Department of Physics, Punjabi University, Patiala, Punjab 147002, India)
• Navneet Kaur(Department of Physics, Punjabi University, Patiala, Punjab 147002, India)
• Apoorva Katoch(Department of Physics, Punjabi University, Patiala, Punjab 147002, India)
• Raminder Kaur(Department of Physics, Punjabi University, Patiala, Punjab 147002, India) Corresponding author