Optimized growth of heteroepitaxial (111) NiFe₂O₄ thin films on (0001) sapphire with two in-plane variants via chemical solution deposition

(111)-oriented epitaxial thin films of nickel ferrite (NFO) are grown on c-plane sapphire [α-Al₂O₃(0001)] substrates using a chemical solution deposition technique. The processing conditions, including pyrolysis and annealing temperatures, are varied to achieve a film that shows maximum texture and epitaxy. It is shown that increasing the pyrolysis temperature to 400°C and decreasing the annealing temperature to 750°C for 10 min result in the highest degree of texture in the films. Lower film thickness also leads to a higher degree of texture. Microstructural studies confirm an in-plane epitaxial relationship between the (111) NFO film and the (0001) Al₂O₃ substrate in two variants, [110] _NFO || [101̄0]Al2O3 or [11̄00]Al2O3.