Deuterium in (Ba,Sr)TiO3 thin films: Kinetics and mechanisms of incorporation and removal during annealing

The kinetics of deuterium doping of and removal from polycrystalline (Ba,Sr )TiO3 (BST) thin films during annealing were investigated using secondary i on mass spectrometry depth profiling, and the data were correlated to chang es in the electrical behavior of the films. Results for deuterium doping of exposed BST films on a Pt bottom electrode layer are consistent with incor poration of deuterium interstitial defects at the BST/Pt interface and "upw ard" diffusion toward the film surface. The incorporation kinetics of deute rium in Pt/BST/Pt capacitors are more complex and are greatly enhanced by t he presence of the Pt top electrode. Removal of deuterium from D-2/N-2-expo sed Pt/BST/Pt specimens during oxygen recovery anneals appears to be limite d by the rate of an interfacial reaction at low temperatures (200-250 degre esC). The pre-D-2 exposure leakage current properties of the BST capacitors were found to be largely recovered when the deuterium concentration in the films was reduced to similar to 10(19) cm(-3) during post-D-2 oxygen recov ery anneals. Recovery annealing in vacuum, although it removed deuterium fr om the films, was found to result in an increase in leakage current density for annealing temperatures greater than 300 degreesC. These results sugges t that introduction of large amounts of positive space charge into the BST films has a pronounced effect on the electrical properties of the Pt/BST in terface. (C) 2001 American Institute of Physics.