CNR ExploRA

Articolo in rivista, 2019, ENG, 10.1039/C8FD00108A

Spectroscopic elucidation of ionic motion processes in tunnel oxide-based memristive devices

Baeumer, Christoph and Heisig, Thomas and Arndt, Benedikt and Skaja, Katharina and Borgatti, Francesco and Offi, Francesco and Motti, Federico and Panaccione, Giancarlo and Waser, Rainer and Menzel, Stephan and Dittmann, Regina

Peter Gruenberg Institute 7, Forschungszentrum Juelich GmbH, JARA-FIT, 52425 Juelich, Germany. Peter Gruenberg Institute 7, Forschungszentrum Juelich GmbH, JARA-FIT, 52425 Juelich, Germany. Peter Gruenberg Institute 7, Forschungszentrum Juelich GmbH, JARA-FIT, 52425 Juelich, Germany. Peter Gruenberg Institute 7, Forschungszentrum Juelich GmbH, JARA-FIT, 52425 Juelich, Germany. CNR, Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Via P. Gobetti 101, 40129 Bologna, Italy CNISM, Dipartimento di Scienze, Universit`a di Roma Tre, Via della Vasca Navale 84, 00146, Rome, Italy Dipartimento di Fisica, Universit`a di Milano, Via Celoria 16, I-20133 Milano, Italy Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, 34149 Trieste, Italy Institute of Materials in Electrical Engineering and Information Technology, RWTH Aachen University, 52056 Aachen, Germany Peter Gruenberg Institute 7, Forschungszentrum Juelich GmbH, JARA-FIT, 52425 Juelich, Germany. Peter Gruenberg Institute 7, Forschungszentrum Juelich GmbH, JARA-FIT, 52425 Juelich, Germany.

Resistive switching oxides are highly attractive candidates to emulate synaptic behaviour in artificial neural networks. Whilst the most widely employed systems exhibit filamentary resistive switching, interface-type switching systems based on a tunable tunnel barrier are of increasing interest, since their gradual SET and RESET processes provide an analogue-type of switching required to take over synaptic functionality. Interface-type switching devices often consist of bilayers of one highly mixed-conductive oxide layer and one highly insulating tunnel oxide layer. However, most tunnel oxides used for interface-type switching are also prone to form conducting filaments above a certain voltage bias threshold. We investigated two different tunnel oxide devices, namely, Pr1-xCaxMnO3 (PCMO) with yttria-stabilized ZrO2 (YSZ) tunnel barrier and substoichiometric TaOx with HfO2 tunnel barrier by interface-sensitive, hard X-ray photoelectron spectroscopy (HAXPES) in order to gain insights into the chemical changes during filamentary and interface-type switching. The measurements suggest an exchange of oxygen ions between the mixed conducting oxide layer and the tunnel barrier, that causes an electrostatic modulation of the effective height of the tunnel barrier, as the underlying switching mechanism for the interface-type switching. Moreover, we observe by in operando HAXPES analysis that this field-driven ionic motion across the whole area is sustained even if a filament is formed in the tunnel barrier and the device is transformed into a filamentary-type switching mode.

Faraday discussions (Print) 213 , pp. 215–230