Study Of The Nonlinear Dielectric Properties Of The Sto Film

STO thin films have become increasing important in voltage tunable microwavecomponents applications because of the strong nonlinear dielectric properties.This requires the growth of high quality thin films,as well as fundamental understanding of the relationship between the microstructure and dielectric properties.Pulsed laser deposition was used to prepare STO thin films in this thesis.Influence of deposition parameters,such aS substrate temperature,oxygen pressure,energy density and pulsed frequency were on the structural and electrical properties of STO thin films were studied.Under optimized growth parameters,STO thin films with high quantities were prepared.The dielectric constant of STO thin film can be changed 76.94%at an applied field of 1 000KV/cm,and the loss tangent keeps only 5%00.The effect of interface,oxygen vacancy,anneal and stress on the electrical properties of STO thin films was discussed in this thesis.In order to get enhanced dielectric properties,smooth interface between STO thin films and electrode Was necessary.Less oxygen vacancies can improve insulative properties of STO thin films.Annealing is important in order to obtain highly textured thin films and excellent voltage tunable properties.The strain would reduce the dielectric constant of STO thin films.while the stress would increase it.When cubic—tetragonal phase transition takes place in STO thin film,the elongatiofl ofthe lattice parameter along the applied field would improve the tunability.