Optical and electrical properties of Nd-doped BiFeO3 thin films and heterostructures

High quality BiFeO3 (BFO) and Bi0.9Nd0.1FeO3 (BNFO) thin films (d = 150-350 nm) were grown at 650-750 degrees C by RF sputtering on dielectric (SrTiO3; ZrO2 < Y >) and conducting (Nb-doped SrTiO3(100); n-type Si) substrates. A direct band gap at 2.57 eV and 2.62 eV (at T=295 K) have been estimated for the BFO/YSZ and BNFO/YSZ films from optical transmittance spectra while an unset of weak absorption has been indicated for the films at 2.20 eV. Transverse electrical transport of the (BFO, BNFO)/(STON, Si) heterostructures revealed nonlinear current versus voltage behavior and clearly defined rectifying properties. Schottky junction model has been applied for the heterojunctions at T=300 K although complicated shape of I-U curves demonstrated increasing role of space charge limited current with T decreasing down to 78 K. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim