Effect of Ti Doping on the Structural and Optical Properties of ZnO:Ti Thin Films Prepared by Electrodeposition
Chukwudi Benjamin Muomeliri *
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Azubuike Josiah Ekpunobi
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Donald Nnanyere Okoli
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Chiedozie Emmanuel Okafor
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Diemiruaye Mimi Jeroh
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Okechukwu Emmanuel Odikpo
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Overcomer Anusiuba
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Adline Nwaodo
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
A. Azubogu
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Lynda Ozobialu
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Onuigbo E
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Onu Chiamaka
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Ikechukwu Chibuogwu
Department of Physics and Industrial Physics, Nnamdi Azikiwe University Awka, Anambra State, Nigeria.
Augustine Nwode Nwori
Department of Industrial Physics, Faculty of Physical Science, Chukwuemeka Odumegwu Ojukwu University Uli, Anambra State, Nigeria.
Nonso Livinus Okoli
Department of Computer Education, Madonna University Okija, Anambra State, Nigeria and Nanoscience and Advanced Materials, Federal University of ABC, Santo Andre, Sao Paulo, Brazil.
*Author to whom correspondence should be addressed.
Abstract
Thin films of metal oxides from Group II elements have demonstrated significant potential for applications across various fields of science and technology. Among them, zinc oxide (ZnO) stands out due to its excellent properties, making it highly suitable for diverse technological applications. Titanium (Ti), a quadrivalent cation, can be incorporated into ZnO as an interstitial dopant, acting as a scattering centre and modifying its properties. In this study, a cost-effective electrodeposition method was employed to synthesise titanium-doped zinc oxide (ZnO:Ti) thin films with varying Ti concentrations, in order to investigate their effects on optical and structural properties. The films were deposited on fluorine-doped tin oxide (FTO) conductive glass substrates using a three-electrode system, with FTO as the working electrode, a platinum rod as the counter electrode, and Ag/AgCl as the reference electrode. Zinc acetate and titanium powder digested with hydrogen fluoride served as sources of Zn, O, and Ti ions, respectively. The deposited thin films of ZnO:Ti were characterised for their optical and structural properties using Uv-Vis spectrometry and X-ray diffraction technique, respectively. The results of the characterizations shown that the optical properties of the films, such as transmittance, refractive index, extinction coefficient and bandgap energy, were influenced by Ti doping. The transmittance (%) was found to decrease for the film (10 ml ZnO:Ti) deposited at the highest Ti concentration in the VIS region, but increased to the highest value in the NIR region. The bandgap energy of the deposited thin films was found to decrease with the concentration of Ti doping. The obtained values were (2.73 – 3.20 eV) for undoped ZnO and (2.73 – 3.18 eV), (2.80 - 3.0 eV), 2.81 eV and 2.60 eV for 4ml, 6ml, 8ml and 10ml ZnO:Ti, respectively. The X-ray diffraction analysis indicated that the fabricated films have crystalline structures which are also influenced by Ti doping. The crystallite size of the films was found to increase while micro-strain decreased as the doping concentration increased, which enhanced the crystal structure for device applications. These findings suggest that ZnO:Ti thin films are promising candidates for applications in transparent thin-film transistors (TTFTs), liquid crystal displays (LCDs), light-emitting diodes (LEDs), transparent electrodes in solar cells, and other optoelectronic devices.
Keywords: Zinc oxide ZnO, titanium, Transparent Conducting Oxides (TCOs), wide bandgap, opto-electronics