OPTIMIZATION OF SRTIO3 FOR APPLICATIONS IN TUNABLE RESONANT CIRCUITS

A series of SrTiO3 (STO) films have been grown at a wide range of depo sition conditions in order to determine the optimal growth parameters to maximize ferroelectric tuning while maintaining the lowest dielectr ic losses. The deposition pressure of the ambient O-2 (40m Torr<P-dep< 800m Torr) and substrate temperature (750 degrees C<T-sub<850 degrees C) was varied independently while the fluence was held constant at 2.0 J/cm(2). The deposited films were characterized by x-ray diffraction (XRD) and low frequency dielectric measurements (1 MHz). The out-of-pl ane STO lattice parameter (a(z)(film)) of the deposited films was foun d by XRD to be a strong function of the deposition pressure: a(z)(film ) < a(bulk) at low pressure (P-dep <65 mTorr) and a(z)(film) > a(bulk) at higher pressures (P-dep>65 mTorr). The dielectric constant (epsilo n(r)) and loss tangent (tan delta) were determined as a function of ap plied field at room temperature (300 K) and at liquid nitrogen tempera ture (77 K). The low frequency dielectric properties of the STO films were found to be a weak function of the strain of the ferroelectric fi lm.