26 d’abril, a les 15:00 hores, ICMAB, Sala d’Actes.
Electrostatics and photoresponse of 2D electron gases in oxide interfaces.
Fabio Miletto Granozio, Umberto Scotti di Uccio, Carmela Aruta, Emiliano Di Gennaro, CNR-SPIN, Complesso Universitario di Monte Sant’Angelo, via Cintia 80126 Napoli, Italy.
The properties of the 2DEGs found at the LaAlO3/SrTiO3, LaGaO3/SrTiO3 and NdGaO3/SrTiO3 interfaces are addressed and compared.
An analysis of atomic displacements and of EEL spectra collected at the Ti L and the O K-edge allows us to estimate the lattice polarization P(z) and the valence state of Ti as a function of the z coordinate across the interface [1]. Our variable wavelength photoconductivity data [2] show a very peculiar response to light common to all polar-nonpolar interfaces. Our interfaces show a persistent photoresponse under both UV (i.e., above STO gap) and visible light. We argue that different absorption mechanisms are at play in the two different cases.
An electrostatic analysis based on our P(z) data allows us to estimate the electric displacement vector D(z), the charge distribution, and the possible location of the electron and hole populations under light irradiation. The data are discussed in the light of the unending debate on the origin of the 2DEG in oxide interfaces.
[1] C. Cantoni et al., Advanced Materials (2012) DOI: 10.1002/adma.201200667
[2] E. Di Gennaro et al., Advanced Optical Materials, (2013) submitted; U. Scotti di Uccio et al, arXiv:1206.5083v1;
