Charge transport and trapping in BaTiO3 thin films flash evaporated on Si and SiO2/Si

BaTiO3 (BT) thin films were prepared by flash evaporation onto p-Si and SiO2/p-Si from a Re boat at 1800 degrees C in ultra high vacuum. The films are amorphous and remain so after a thickness reduction by 10-20% upon annealing at 500 degrees C for 3 min in O-2 atmosphere. Annealing raises, also, the index of refraction by some 5% and the extinction coefficient by a factor of 2. Electron injection at the Al to BT interface of Al/BT/Si capacitors is enhanced by the Schottky effect, yielding a value of 11.2 for the dielectric constant of BT. Modeling current-time measurements yields a trap density of 10(24) m(-3), 0.82 eV below the conduction band, Capacitance-voltage curve shifts due to bias stress on Al/BT/SiO2/Si capacitors are interpreted as caused by electron injection and trapping in the BT films. Starting deposition at 170 degrees C or postdeposition annealing reduces the trap density and increases the capacitance-voltage curve shifts by bias stress, from 0.3 to over 14 V at bias stress of -10 V. (C) 1999 Elsevier Science S.A. All rights reserved.