Ferroelectric field effect in (La,Sr)CoO3/Pb(Zr,Ti)O-3/(La,Sr)CoO3 heterostructures

Epitaxial LaCoO3/Pb(Zr,Ti)O-3/(La,Sr)CoO3 (LSCO) heterostructures have been grown on LaAlO3 by pulsed laser deposition for investigating ferroelectric field effect. In the heterostructure, semiconducting LaCoO3 was used as a conducting channel layer, instead Si. The resistivity of the LaCoO3 (LCO) channel layer was found to be dependent on an oxygen ambient, primarily the ambient oxygen pressure during deposition. The resistivity of the LCO layer varied in the range of 0.1 - 100 Ohm cm. Ferroelectric field effect induced in LaCoO3 layer was observed by measuring the resistance modulation of the LCO layer with respect to the polarized state of the PZT layer. The resistance modulation of 9 % was obtained in the 680 Angstrom thick LCO layer. Further the resistance modulation was improved up to 45 % after applying dc bias. It is suggested that the LCO/PZT/LSCO heterostructure can be used as a ferroelectric field effect transistor.