Special seminar by Dr. Konstantinos Konstantinou

Save the date! OCAMM presents a special seminar by Dr. Konstantinos Konstantinou from the University of Turku, who will talk about atomistic simulations of phase-change materials for aerospace applications. This invited seminar will take place at the Department of Chemistry and Materials Science, Aalto University on 1 November 2024 @ 13:15 in lecture hall D311 (Ke5) at the main building of the School of Chemical Engineering in the Otaniemi campus, Kemistintie 1, 02150 Espoo. The seminar is open to all. Please join us in Otaniemi to find out how order/disorder transitions in a material can be used to construct nanoscale computer memories!

Title

Non-volatile phase-change memory for spaceship application

Abstract

Radiation-hard non-volatile memories are in high demand by the space community for implementation in microcontrollers and solid-state data recorders. In phase-change memories, binary data are represented as changes in structural phase rather than by stored electrical charge; thus, these devices are supposed to be tolerant to ionizing radiation effects. Ion irradiation corresponds to a process that involves the production of non-equilibrium cascades in the host material, and the atomistic modelling of such events in glasses is challenging. Here, radiation damage in amorphous Ge₂Sb₂Te₅ phase-change memory material is modelled by carrying out thermal-spike simulations with ab initio molecular-dynamics calculations. A stochastic boundary-conditions approach is employed to treat the thermal nature of the cascades and drive the modelled system back to equilibrium in a natural way. The dynamics of the cascade evolution shows that the time-scale of the ballistic phase of the cascade inside the glass model is very short. Investigation of the atomic geometry highlights a structural recovery from the damage imposed during ion irradiation, since the glass manages to maintain its amorphous network. Analysis of the bonding for all the species in the glass structure reveals particular structural modifications in the local atomic environments and the connectivity of the amorphous network. Overall, the simulations manifest the remarkable ability of Ge₂Sb₂Te₅ phase-change memory material to be radiation-tolerant, hence indicating its potential applications in future space and other radiation-present environments.

About the speaker

After completing his MSc degree in Computational Physics at the Aristotle University of Thessaloniki in Greece, Konstantinous moved to the UK to obtain a PhD in Physics from University College London. He then joined the University of Cambridge as a research associate in Chemistry. Konstantinos came to Finland in 2020 as postdoctoral researcher in Tampere University before joining the University of Turku, where he currently holds the prestigious Academy Fellow position. His current research interests include defects in amorphous semiconductors, resistive switching memories, machine-learned molecular-dynamics simulations, charge trapping processes, and electronic excitations, among others.