Bart J. Kooi studied Materials Science at Delft University of Technology and received, under supervision of prof. Eric Mittemeijer, his PhD degree in 1995 with a thesis entitled “Iron-Nitrogen Phases: Thermodynamics, Long-Range Order and Oxidation Behaviour”. Then he moved to the University of Groningen to work as assistant and associate professor in the research group Materials Science headed by prof. Jeff De Hosson with a main focus on transmission electron microscopy of nanostructured materials and interfaces. In 2001 he started research on phase-change materials for memory applications which developed in a broader interest in chalcogenide and antimonide materials. In 2009 he established his own research group “Nanostructured Materials and Interfaces” within the Zernike Institute for Advanced Materials, where he also started extensive research collaborations with companies: NXP, Micron Technologies, ST Microelectronics, Photonis, Tata Steel and IBM. He is in charge of advanced electron microscopy facilities, where recently he was able to image for the 1^st time in history hydrogen atoms in a metal hydride. He has published more than 240 articles in peer-reviewed journals with as overarching theme nanostructure-property relations. He is chairman of the program committee of the annual conference series E\PCOS (European Phase Change and Ovonic Sciences) since 2016 and received the Ovshinsky Lectureship Award 2021 for outstanding contribution to Ovonic Science and Technology.

Selected Publications 

1. Sytze de Graaf, Jamo Momand, Christoph Mitterbauer, Sorin Lazar, Bart J Kooi, Resolving hydrogen atoms at metal-metal hydride interfaces, Science Advances 6 (5), eaay4312, 2020, (DOI: 10.1126/sciadv.aay4312)

Hydrogen atoms are imaged with atomic resolution for the first time at the interface between a metal and a metal hydride and for the first time robustly in a metal hydride by employing a new technique, integrated differential phase contrast, in aberration corrected scanning transmission electron microscopy (AC-STEM).

1. Reversible oxygen migration and phase transitions in hafnia-based ferroelectric devices, Pavan Nukala, Majid Ahmadi, Yingfen Wei, Sytze de Graaf, Evgenios Stylianidis, Tuhin Chakrabortty, Sylvia Matzen, Henny W Zandbergen, Alexander Björling, Dan Mannix, Dina Carbone, Bart Kooi, Beatriz Noheda, Science 372, 630-635, 2021 (DOI: 10.1126/science.abf3789)

Atomic resolution imaging of reversible oxygen migration in a cross-section stack of complex oxide layers by in-situ electrically biasing (with opposite polarities) in an advanced AC-STEM. Strong increase in switching speeds as measured in-situ (when going from 1 to 3 V) can be coupled well to fast switching in electrical devices (at 6 V).

1. Bart J. Kooi, Matthias Wuttig, Chalcogenides by Design: Functionality through Metavalent Bonding and Confinement, Advanced Materials 32, 1908302, 2020 (DOI: 10.1002/adma.201908302)

Review paper where an initial part focuses on the special type of bonding present in Te, Sb and Se based materials, making them highly suitable for thermoelectric, phase change memory, topological insulator or switchable photonics applications. A second part focuses on interesting effects that arise in these materials when they are confined in reduced dimensions down to the nanoscale, where, in particular, the crystallization kinetics of thin films and nanoparticles is discussed in detail.