Comparative Investigation of Optical and Electrical Properties of Pure and Ag/Sn Doped TiO₂ Thin Films Synthesized via Sol–Gel Dip Coating Technique
Keywords:
TiO₂ thin films, Sol–gel method, Dip coating, Ag doping, Sn doping, Optical properties, Electrical conductivity, Band gap engineeringAbstract
- a) Background: Optoelectronic and energy applications make extensive use of TiO₂ thin films. Their characteristics are heavily influenced by doping effects, flaws, and structure. Sol-gel dip coating makes it possible to fabricate thin films in a controlled and economical manner. Band structure and electrical transport characteristics are drastically altered by doping.
- b) Objective: The optical and electrical characteristics of doped TiO₂ films are examined in this work. Ag and Sn doped systems were compared. Relationships between structure and properties were determined for both doped systems.
- c) Methods: Precursor solutions were made using the sol-gel technique under carefully regulated hydrolysis conditions. Dip coating used controlled withdrawal speed and repeated cycles to deposit films. Defect-free, homogeneous film formation was guaranteed by intermediate drying. Organic residues were eliminated and crystallinity was enhanced by annealing at 450°C. Electrical, UV-Vis, SEM, and XRD measurements were carried out in a methodical manner.
- d) Results: In every thin-film sample, anatase phase development was verified. Ag doping used a grain boundary pinning method to decrease crystallite size. Lattice strain and defect concentration were greatly boosted by Sn doping. Following doping, optical absorption increased with visible region shift. The band gap dropped to lower values from about 3.2 eV. The samples with the largest band gap reduction were Sn-doped films. Increased charge carrier density led to an increase in electrical conductivity. When compared to Ag-doped films, Sn-doped films showed greater conductivity.
- e) Comparison with Literature: The observed anatase phase is consistent with sol-gel TiO₂ systems that have been reported. Ag-induced grain refinement is consistent with previously described boundary pinning mechanisms. Defect and lattice distortion models are consistent with Sn-induced strain. Defect-state and band tailing theories are consistent with band gap narrowing. The reported oxygen vacancy transport pathways are consistent with electrical trends.
- f) Conclusion: TiO₂ films' optical and electrical characteristics are efficiently tuned by doping. Ag doping uses plasmonic interactions to improve optical absorption. Electrical conductivity is enhanced by Sn doping through defect generation mechanisms. The applicability for optoelectronic and energy device applications is confirmed by the results.
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