Electrical conduction transition and largely reduced leakage current in aluminum-doped barium strontium titanate thin films heteroepitaxially grown on Ir/MgO/Si(100)

Ba0.6Sr0.4Ti1-xAlxO3 (BSTA, x=0, 3 at. %, 6 at. %) thin films have been prepared on Ir/MgO-buffered silicon substrates by pulsed-laser deposition. All-epitaxial growth of BSTA/Ir/MgO/Si heterostructures has been evidenced by x-ray diffraction and reflection high-energy electron diffraction. A large reduction in the leakage current density of BSTA thin films was observed by aluminum doping. For 3 at. % Al-doped BSTA thin films, the dominant conduction mechanism shows space-charge-limited current behavior at a low electric field, where the trap-filled limit field is determined as E-TFL = 10 KV/cm, while at a high electric field the Poole-Frenkel emission is operative. In contrast, the conduction mechanism for 6 at. % Al-doped BSTA thin film is dominated by field-enhanced Schottky emission. (C) 2005 American Institute of Physics.