Skip to content
Skip to navigation menu

Physics Seminar

Simulating chalcogenides: From phase-change memory to quantum-dot solar cells

Speaker: Dr Felix-Cosmin Mocanu (Ecole Normale Superieure de Paris)
Date: Wednesday 24 February 2021
Time: 15:00 in UK
Venue: Zoom

In this talk I will review some of the recent advances made in simulating functional chalcogenides with a particular emphasis phase-change memory materials. Phase-change memory materials display a fast transition between an amorphous and a crystalline phase which have a large reflectivity/resistivity contrast that can be exploited for optical/electronic memory devices. The origin of the fast amorphous to crystalline transition can be found in the fast mobility of atoms in the galssy phase, the bonding similarities between the amorphous and crystalline phases, and the large driving forces towards chemical ordering upon annealing. Given the promising downscaling of these devices (to about ~2nm) and the fast switching speed (up to ~0.5 ns), these materials are ideally suited for study by density functional theory calculations, which were able to capture the crystallization. DFT data can be further leveraged using machine learning techniques to run larger and longer timescale simulations [1, 2]. Furthermore, stochastic boundary conditions enable the investigation of non-equilibrium dynamics of the glassy phase including the effects on ion irradiation and estimating the thermal conductivity [3, 4].

Time permitting, I will discuss some recent work on PbS quantum dots used in solar cells and in particular the influence of solvents on the surface energy and quantum dot morphology.

[1] FC Mocanu, K Konstantinou, TH Lee, N Bernstein, VL Deringer, G Csányi, SR Elliott The Journal of Physical Chemistry B 122 (38), 8998-9006
[2] K Konstantinou, FC Mocanu, TH Lee, SR Elliott Nature communications 10 (1), 3065
[3] K Konstantinou, TH Lee, FC Mocanu, SR Elliott Proceedings of the National Academy of Sciences 115 (21), 5353-5358
[4] FC Mocanu, K Konstantinou, SR Elliott Applied Physics Letters 116 (3), 031902

Biograpahy: Felix-Cosmin Mocanu obtained his PhD in Chemistry in November 2019 from the University of Cambridge, co-advised by Stephen Elliott and Gabor Csanyi. During his doctoral studies he focused on the physics of amorphous semiconductor materials with resistive switching, as used in electronic phase-change memory devices. In parallel he worked on fitting the high-dimensional potential energy surfaces of these materials using kernel-based machine learning techniques. In December 2018 he started a postdoc in the Electrical Engineering Department in Cambridge with Prof. Jong Min Kim on the physics of semiconducting quantum dots and amorphous oxides, for display and smart textile applications. Since July 2020 he is a postdoctoral researcher Laboratoire de Physique Theorique at Ecole Normale Superieure, in Paris, working with Francesco Zamponi and Ludovic Berthier on the properties of glassy systems at low temperatures.