V. M. Rizak

D. Sc., Prof.

V. M. Rizak was born on July 10, 1963 in the village of Bobovyshche, Mukachevo district, Zakarpatska Oblast. In 1980, he graduated with a gold medal from Bobovyshche Secondary School and entered the Faculty of Physics of Uzhhorod State University. The entire scientific biography of V. M. Rizak is associated with Uzhhorod University. He graduated with honours from the Faculty of Physics of Uzhhorod State University (1985). From 1985 to 1988 – a graduate student of the Department of Semiconductor Physics, Uzhhorod State University. In March 1989 he defended his dissertation, since 1996 – Doctor of Physical and Mathematical Sciences. In 1988–1993 he became a junior, scientific, and senior researcher at the Fundamental Research Laboratory of Synthesis and Complex Studies of the Properties of New Semiconductor Substances of the Composite Structure of Uzhhorod University. Since 1993 he has been engaged in scientific and pedagogical activities as an assistant, associate professor (1994), professor of the Department of Semiconductor Physics (1997), and since 2002 – Head of the Department of Solid-State Electronics of Uzhhorod National University (since 2007 – Department of Solid-State Electronics and Information Security).

After defending his dissertation, he continued the study of critical phenomena in dielectrics and semiconductor crystals, the development of new materials with pyro- and ferroelectric properties. This allowed to develop a new scientific area in physics – the study of anharmonicity, nonequilibrium, and fluctuation effects in semiconductor dipole systems with polycritical points (Lifshitz point, tricritical point, tricritical Lifshitz point). Experimental installations for studying the temperature behaviour of heat capacity, thermal conductivity, electrical conductivity, dielectric constant, and studying the influence of uniaxial pressure on the electrophysical and optical properties of crystals have been created. New important results in the field of semiconductor physics have been obtained. For the first time, an inelastic incoherent scattering of thermal neutrons was studied for Sn2P2S6 crystals, the densities of phonon states were calculated, and the main thermodynamic parameters were calculated. For ferroelectrics-semiconductors of the Sn2P2S6 type, the effect of thermo-optical memory and anomalous birefringence hysteresis were found in the disproportionate phase. In the vicinity of the structural phase transition and at temperatures above twice the Debye temperature, abnormally low absolute values of the thermal conductivity and the effect of changing the sign of the thermal conductivity anisotropy in the ferroelectric phase were identified. It is proved that the critical behaviour of birefringence during the phase transition from the vapour to the disproportionate phase of the crystal satisfies the two-component three-dimensional Heisenberg model. A substantial deviation from the monoharmonic approximation of the form and anomalies of the temperature dependence of the isobaric heat capacity and birefringence at the low-temperature boundary of the disproportionate phase of the uniaxial ferroelectrics is found. The microscopic mechanism of ferroelectric phase transition and occurrence of disproportionate phase in Sn2P2S6 type crystals is established.

Together with his brother, I. M. Rizak, Candidate of Physical and Mathematical Sciences and Professor D. H. Semak, V. M Rizak founded the Department of Applied Physics at the Faculty of Physics of Uzhhorod National University and opened the specialty "Science-intensive physical technologies" towards specialisation development "physical and technical examination" and substantial work was performed to develop the infrastructure for training experts in this field.

On V. M. Rizak's initiative and with his direct active participation, for the first time in Zakarpattia, the Department of Solid-State Electronics and Information Security (SSEIS) of Uzhhorod National University headed by him began training specialists in the educational and professional field "Information Security Systems", and in 2010 – Security of information and communication systems of the field of knowledge "Information Security". In 2011, the SSEIS Department accredited the training of "Information Security Systems" and received a license to train specialists and masters in "Information Security Systems, Processing Automation", which was successfully accredited in 2012. In 2014, the area of training "Security of Information and Communication Systems" was accredited and a license for training masters of this specialty was obtained.
Since 2008, the SSEIS Department of Uzhhorod National University has been training students to obtain additional qualifications "Teacher of Computer Sciences".
An important achievement of the SSEIS Department in 2010 became the establishment of the first-ever branch of the university in the capital of Ukraine (Institute of Mathematical Machines and Systems of the National Academy of Sciences of Ukraine) for internships and research work on technical protection of information. A branch of the department was established in the Department of Functional Electronics Materials (Head of the Department Prof. O.V. Homonai) of the institute of Electronic Physics under the national Academy of Sciences of Ukraine.

International relations are intensifying, as evidenced by the implementation of Ukrainian-Hungarian, Ukrainian-Slovak, Ukrainian-Indian, Ukrainian-Turkish projects, NATO and TACIS grants. Economic contracts with enterprises in the region have been renewed.

Along with scientific and pedagogical activities at Uzhhorod University, V. M. Rizak made a lot of efforts to organise support for regional science, founded and headed a fund to support science, the main task of which was to preserve scientific schools in the region, support priority areas, intensive involvement of young people in research activities. The foundation has contributed to the publication of more than 30 scientific manuals, methodological developments and monographs of both natural and humanitarian profile. Rizak organises conferences, round tables, sponsors international seminars and conferences. The fund includes financial aid to schools, payment for Internet for Uzhhorod National University doctors, sponsorship of business trips to scientists and other representatives of the creative intellectuals. Therefore, for a considerable contribution to the development of science and active participation in the socio-political life of the region, V. M. Rizak was awarded a diploma of the head of the regional state administration (1998), and for supporting academic science – a jubilee medal on the occasion of the 80th anniversary.

V. M. Rizak has co-authored more than 200 published scientific articles, including monographs and training aids and textbooks with the stamp of the Ministry of Higher Education of Ukraine, in particular "Physics of nonequilibrium phenomena in semiconductors" (Uzhgorod, 1998), "Photothermostructural transformations of chalcogenides" (Uzhhorod, 1999), "Functional chalcogenide semiconductors" (Uzhhorod, 2001), "Solid State Chemistry" in two parts (Uzhhorod, 1999, 2002), "Heterogeneous Equilibria" (Uzhhorod, 2003), "Structural and Functional Materials" in two parts (Kyiv, 2003, 2004), "Mechanics in examples and problems" (Uzhhorod, 2004), "Cryogenic physics and technology" (Kyiv, 2006).

Rizak's scientific activity contributed to the development of candidates of physical and mathematical sciences S. I. Perechynskyi, I. M. Rizak, O. O. Bokotei, a Syrian K. Al-Shufi. Two candidate dissertations were defended under Rizak's supervision (O. I. Chobal, I. I. Trikur).

Rizak received a personal grant from the International Science Foundation (ISSEP).

In May 2003 he was elected a full member of the Academy of Engineering Sciences of Ukraine. Since 2003 V. M. Rizak has been a foreign member of the Scientific Council of the Hungarian Academy of Sciences. In 2004 he was awarded the honourary title of "Honoured Worker of Science and Technology of Ukraine". Since 2006 – Editor-in-Chief at "Scientific Bulletin of Uzhhorod University. Physics Series". Member of the Coordinating Council of the Ukrainian Physical Society since 2004, and since 2010 – heads the Transcarpathian branch of the Ukrainian Physical Society.

At present, V. M. Rizak fruitfully cooperates with scientists from the Czech Republic, Italy, Sweden, Poland, Slovakia, Hungary, etc. His studies are presented in the world's leading journals on physics (Phys. Rev., JETP, Phys. St. Sol., Bulletin of the Academy of Sciences of USSR: Physics Series, Solid State Physics, Ferroelectrics, Crystallography, Physics and Chemistry of Glass, Ukrainian Physical Journal, etc.).