Impact of microstructure on the electrical stress induced effects of pulsed laser ablated (Ba, Sr)TiO3 thin films

Electrical stress induced degradation effects in thin films of (Ba, Sr)TiO3 were studied. A comparison of the processing conditions of the films was m ade to examine its subsequent impact on the electrical stress induced degra dation in this regard. Films from two different processing approaches were taken up for this study, which had different microstructures and grain size s originating from their difference in annealing/thermal conditions. A cont inuous electron injection under low field conditions was found to cause a c hange in the capacitance and the leakage current characteristics of the thi n films. It is generally observed that the process of electron injection ca uses an accumulation of charge at the trap sites, thereby changing the loca l field near the vicinity of the trapped charge. This leads to the change i n the electrical properties, such as the capacitance of metal-insulator-met al capacitors as observed. Capacitance-voltage (C-V) measurements were perf ormed to estimate the electronic capture cross section and the neutral trap density from the voltage shifts induced in the C-V curves. The trapping ef ficiency, capture cross section, and trap densities were obtained as functi ons of the injected charge fluence. The obtained values showed that in situ crystallized films exhibited better electrical response under continuous e lectrical stress than those which were ex situ crystallized. However, time- dependent dielectric breakdown studies (long-term response) on the two type s of films indicated that ex situ crystallized films are more resistant tow ard breakdown than their in situ crystallized counterparts. The observation s showed that the microstructure played an important role in the degradatio n properties. The electrical breakdown in both cases is believed to origina te from different parts of the film. In the case of the ex situ crystallize d films the breakdown takes place at the grain boundaries, while in the in situ case it appears to originate at the electrode/film interfaces. (C) 200 0 American Institute of Physics. [S0021-8979(00)02506-8].