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Electrical and magnetic properties of p-n diode structures based on lanthanum manganites and Nb-doped SrTiO3

Bonifacas Vengalis 1Renata Butkute 1Fiodoras Anisimovas 1Antanas K. Oginskis 1Jelena Devenson 1Vytas Pyragas 

1. Semiconductor Physics Institute, A.Gostauto 11, Vilnius LT-2600, Lithuania


There is increasing interest in p-n junctions formed between hole-doped manganite films and conducting n-type SrTiO3<Nb> (STON). In this work, high quality La2/3Ba1/3MnO3 (LBMO), La2/3Ca1/3MnO3 (LCaMO) and La2/3Ce1/3MnO3 (LCeMO) thin films were grown in-situ at 750°C on Nb 0.1 wt % doped conducting STON substrates by pulsed laser deposition and dc magnetron sputtering. Our attempts were undertaken to elucidate a role of dopant element (Ba, Ca and Ce), deposition conditions and possible lattice mismatch at the interface on electrical and magnetic properties of the heterostructures. Current perpendicular to plane geometry was used to investigate the junction resistance, magnetoresistance, the current-voltage (I-U) and capacitance-voltage (C-U) characteristics of the prepared LBMO/STON, LCaMO/STON and LCeMO/STON heterostructures. Asymmetric I-U relations measured at T=78÷300 K for all the heterostructures including LCeMO/STON certified hole doping of the films. The characteristic values of diffusion voltage, corresponding to a steep current increase at a forward bias have been estimated. Magnetoresistance and magnetic field-dependent C-U characteristics were measured at various temperatures to model charge distribution in the vicinity of the p-n junctions. It was found in this work that the effect of epitaxial strain on band gap of the manganites (LCaMO/STON) as well as enhanced phase separation phenomenon at the (LCeMO/STON) interface influence strongly nonlinear I-U characteristics of the heterojunctions. Microstructure of the manganite films, possible strains and oxygen diffusion in the interface region were found to be of key importance for the controlled fabrication of the manganite heterostructures.


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Presentation: Oral at E-MRS Fall Meeting 2006, Symposium K, by Bonifacas Vengalis
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-16 09:31
Revised:   2009-06-07 00:44