Effect of Ni Doping on the Structural and Optical Properties of ZrO 2 Thin Films
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https://doi.org/10.1007/s11664-020-08558-0 Ó 2020 The Minerals, Metals & Materials Society
Effect of Ni Doping on the Structural and Optical Properties of ZrO2 Thin Films DAVINDER KUMAR,1 AVTAR SINGH,1 B.S. SAINI,2 B.C. CHOUDHARY,3 VANDANA SHINDE,4 and RAMINDER KAUR5,6 1.—Department of Physics, Punjabi University, Patiala, Punjab 147002, India. 2.—Department of Mechanical Engineering, Punjabi University, Patiala, Punjab 147002, India. 3.—Applied Science Department, National Institute of Technical Teachers Training and Research, Chandigarh 160019, India. 4.—Department of Physics, Kavayitri Bahinabai Chaudhari North Maharashtra University, Jalgaon 425001, India. 5.—Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab 147002, India. 6.—e-mail: [email protected]
Transparent thin films of pure and nickel-doped ZrO2 with doping levels of 0, 1, 3 and 5 molar percentage were deposited through sol–gel dip coating and subsequently annealed at 500°C. Surface morphology and film thickness were examined through field emission scanning electron microscopy, which revealed a smooth surface morphology of the synthesized film, while elemental dot-mapping confirmed uniform distribution of nickel in the film. X-ray diffraction analysis revealed tetragonal crystalline structure of the deposited films. The structure exhibited a change in crystallite size upon varying the doping concentration. UV–Visible spectroscopy was employed for determining the optical band gap and transmittance. All the specimens were found to exhibit transmittance above 80%. Surface defects and oxygen vacancies were analyzed through photoluminescence spectroscopy. The photoluminescence peak intensities were observed to decrease upon increasing the nickel doping beyond 1% molar ratio, which was found to be in accordance with the change in optical band gap determined through UV–Visible spectroscopy. Fourier transform infrared spectroscopy revealed a strong absorption peak corresponding to Zr–O vibrational mode, while another peak corresponding to Ni–O vibrational mode was observed for nickel-doped samples, thereby implying replacement of some Zr4+ ions by Ni2+ ions in the lattice. Key words: Nickel doping, zirconium dioxide, crystallite size, optical band gap, transmittance
INTRODUCTION Zirconium dioxide (ZrO2), commonly known as Zirconia, is one of the most interesting transition metal oxides and exhibits novel physical, optical and electronic properties, such as high transparency in ultra-violet and visible regions, high optical band gap, high melting point and a large dielectric constant.1–7 These properties are linked to its band structure, which in turn is significantly affected by
(Received May 26, 2020; accepted October 9, 2020)
microstructural parameters such as crystallite size, nature of defects and crystal phases.8,9 As is the case with most crystalline materials, zirconium dioxide transforms to phases exhibiting higher symmetry upon increasing the temperature. It has been known for a long time that in its bulk form,
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