Study of the ferroelectric properties of epitaxially strained SrTaO2N by means of DFT all-electrons first principles calculations

ALONSO ROBERTO EMILIO; TAYLOR, MARCELA A.; GIL REBAZA, ARLES V.; CAPPELLETTI, MARCELO; FERNÁNDEZ, VICTORIA

Cuenca

Workshop; XIII Reunión Nacional de Electrocerámica; 2017

Sociedad Española de Cerámica y Vidrio (SECV)

tRecently, ferroelectric behavior was observed in compressed SrTaO2N thin films epitaxi-ally grown on SrTiO3substrates. Piezoresponse force microscopy measurements revealedsmall domains (101?102nm) that exhibited classical ferroelectricity, a behavior not previ-ously observed in perovskite oxynitrides. The surrounding matrix region exhibited relaxorferroelectric-like behavior. Bulk SrTaO2N samples do not show ferroelectricity, thus sug-gesting that the origin of it may be related with the strain induced by the substrate.Ab-initio calculations reported that the small domains and the surrounding matrix hadtrans-type and a cis-type anion arrangements, respectively, but do not describe the exper-imentally observed equilibrium phase, nor the strain dependent polarization. In this work,we present high accurate all-electron first-principles calculations on the different possiblelocal structures that can explain the ferroelectric-like properties of the strained material.The determined local structure and oxygen/nitrogen ordering has been related with polar-ization and epitaxial strain. The potential energies and polarization as functions of thein-plane lattice constant are reported.