Ferroelectric tunnel junctions

with Andreas Ruediger

Professor
Institut National de la Recherche Scientifique, Québec

Abstract: Most of us have calculated the particle in a box more or less passionately and yet, few of us wondered what would happen if the particle “saw” a dipole inside the barrier. Does the orientation of the dipole affect the tunneling probability? Under certain conditions it does which paves the way for a resistive memory based on two switchable tunneling probabilities on a ferroelectric platform for which extreme fatigue-resistance had been accomplished since the early 2000s. About 10 years later, ferroelectricity was eventually reported in a cmos-compatible material system of Hf0.5Zr0.5O2 and it did not take long until our group coincidentally produced the first ferroelectric tunnel junctions based on this material.

The presentation will cover the physics of these tunnel junctions, their recent progress, competing charge transport mechanisms, and some “dos and don'ts”  in the phase diagram of Hf0.5Zr0.5O2 when it comes to attaining the metastable, orthorhombic, ferroelectric phase. The presentation will conclude with the recent observation of negative feedback mechanisms in neuromorphic components based on these tunnel junctions which opens the bifurcation way to deterministic chaos with opportunities for random number generation (even at cryogenic temperatures) and new failure mechanisms in neural networks.

Biography: Andreas Ruediger received his PhD in experimental physics from University of Osnabrück in 2001, followed by two years of postdoc fellowship as Feodor-Lynen-Fellow of the Alexander-von-Humboldt foundation with J.F. Scott in Cambridge, UK. From 2003 to 2008, he was head of the nanoarchitecture laboratory at Forschungszentrum Jülich, Germany in the group of R. Waser before joining Institut national de la Recherche Scientifique (INRS) near Montréal. His group is working on size effects of nanoscale polar oxides and their applications in resistive memories, neuromorphic circuits and photocatalysis. His lab operates an RF magnetron sputtering system and several surface characterization tools (confocal Raman imaging, functionalized atomic force microscopy and tip-enhanced Raman spectroscopy). He teaches both mandatory graduate classes (“energy" and “materials") and is program director for an MSc program of sustainable management. When he is not spending the remaining time as president of the professor’s union, you might find him with his family building a cabin in the woods. 

Free Refreshments: Coffee, Cookies, and Fruit