Temperature effects on charge retention characteristics of integrated SrBi2(Ta,Nb)2O9 thin film capacitors were examined in the temperature range of 27–150°C. The decay in remanent polarization at 27°C was linear in logarithmic time from 10−3 to 105 s with a decay rate of 0.24 μC/cm2 per decade. The elevation of storage temperature resulted in an instantaneous decrease in remanent polarization, while the decay rate at elevated temperatures after the instantaneous decrease was as small as that at 27°C. The instantaneous decrease in remanent polarization caused by elevating the temperature was explained by the temperature dependence of spontaneous polarization in the vicinity of the second order transition temperature. The development of asymmetry in the hysteresis loop during high temperature storing indicates that the logarithmic time dependence of the decay in remanent polarization is due to redistribution of space charges rather than polarization reversal.

A new measurement of the thermodynamic temperature interval between the silver and the gold freezing points with an infrared pyrometer has been carried out. The value of the freezing point of gold, referred to the value of the silver point on the IPTS-68, thus obtained, is 1337.41 K (a= 0.059 K). The ratio of the spectral radiances a t the two points is 2.4428 (a= 1.2 . 10-3) at the meaneffective wavelength&= 0.9980ym (a= 0.3 nm). The resulting temperature interval is 0.17 K shorter than the IPTS-68 interval between the same points.

The polarization decay process in SrBi2(Ta, Nb)2O9 capacitors and retention characteristics of a 288-bit ferroelectric memory device fabricated from SrBi2(Ta, Nb)2O9 were studied. The remanent polarization decay at room temperature showed good linearity when plotted against logarithmic retention time over a wide range of 10-3–105 s. The distribution of times to failure of a 288-bit memory was fit to a model having a linear relationship between log (log t f) and 1/T for the period of infant failures and to the Arrhenius model having the form log t f vs 1/T for the period of random failures, where t f is the time to failure and T is the temperature. The activation energy was found to be 0.35 eV for infant failures and 1.15 eV for random failures. Possible causes for the difference in activation energies are discussed.

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Changes in the electrical properties of poled ferroelectric SrBi 2 (Ta,Nb) 2 O 9 (SBTN) thin-film capacitors caused by hightemperature storage were studied. Current-voltage (J-V) characteristics of SBTN capacitors before and after high-temperature storage indicated that the current in SBTN is predominantly carried by electrons and limited by electrode interfaces. The voltage shift in the polarization-voltage (P-V) curve caused at high temperatures was ascribed to a bulk effect because there were no definite changes in the interface-limited J-V characteristics before and after high-temperature storage. Assuming the pinning of domains by capturing electrons emitted from traps distributed in the energy gap, we describe the decay in switchable polarization with the power of time. The activation energy for the decay in switchable polarization associated with electron capture was determined to be 0.23 eV based on the temperature dependence of the decay in switchable polarization.