Strontium titanate crystals are an important base material for superconducting layers (e.g. extremely sensitive magnetic field sensors) as well as for novel electronic applications which exploit the interesting properties of oxide layer structures. These include switchable resistors (memristors), interface conduction and non-volatile memories by controlled formation of ferroelectric domains. At the Leibniz-Institut für Kristallzüchtung (IKZ), a crystal growth technique was developed to produce strontium titanate crystals from the melt with very high structural quality. Dirk Kok supported this project with his doctoral thesis, in which he investigated the influence of growth conditions on optical properties. The results and models found and published by him show application-relevant correlations between the growth atmosphere, the stoichiometric deviation in the crystal and the associated change of the lattice parameter. His observations on the course of temperature-dependent thermal conductivity and band gap are applicable to many other complex oxide materials.
During his chemistry studies at Radboud University in Nijmegen, the Netherlands, Mr. Kok already became familiar with crystallization topics. The doctoral thesis was written from 2013 to 2017 at the Leibniz-Institut für Kristallzüchtung (IKZ) in the group Oxides and Fluorides under the direct supervision of Dr. Christo Guguschev, PD Dr. Detlef Klimm, Dr. Klaus Irmscher and Prof. Dr. Matthias Bickermann. After a successful defense at the Humboldt-Universität zu Berlin, Mr. Kok worked at the Helmholtz-Zentrum Berlin on the synthesis of tungsten bronzes (department of Priv.-Doz. Dr. Klaus Habicht). From May 2019 he will return to Radboud University Nijmegen for a postdoctoral position (group of Prof. Elias Vlieg).
With the DGKK Young Scientists Award, the association honors outstanding scientific achievements of young scientists in the field of crystal growth. The award is worth 2.500 € and the ceremony will take place on 20 March 2019 at the DGKK Crystal Grower Conference in Poznan (Poland). Dirk Kok shares the prize for 2019 with Dr. Pascal Puphal from PSI Villingen (Switzerland).
