Manipulation of dielectric permittivity of sol-gel SrTiO3 films by deposition conditions

Structure, microstructure and low-temperature dielectric properties of undoped SrTiO3 (STO) thin films prepared by sol-gel and deposited on Si/SiO2/TiO2/Pt substrates are studied. The effect of annealing temperature and of buffer layers on properties of STO films is analysed. Dielectric permittivity epsilon', relative tunability n(r) and polarization P are lowest for STO films prepared without buffer layers and annealed at 750 degrees C and are highest for films prepared with buffer layers and annealed at 900 degrees C. The increase of c/a ratio for films with buffer layer and of the grain size for films annealed at higher temperature is used to explain the improved dielectric response. The dielectric permittivity of STO films prepared by low-cost sol-gel technique with optimized deposition conditions is found to be comparable to that of STO films fabricated by more sophisticated and expensive methods such as pulsed laser deposition.