Doctoral Theses

“Electronics and photonics”

  • Theme: Memristive sensorics for post-digital electronics
    Supervisor: Ing. B. Hudec, PhD. ( Department of III-V Semiconductors )
    Abstract:
    In-sensor computing is a new paradigm for 21st century electronics inspired by nature. In present-day electronics, all the noisy, unstructured data output by sensors needs to be digitised first for further processing. This may soon become a showstopper given the exponential rise in the amount of sensing devices and data they produce, both in consumer electronics like self-driving vehicles and in the Industrie 4.0 framework. On the other hand, in bio-inspired systems, the sensing and processing are not separate; instead, the sensing nodes directly form synaptic connections in the hardware neural network, where the external stimuli being sensed directly alter the synaptic weight matrix, allowing simple algorithms encoded in the neural network to process the signals into reasonable output in real-time.
    Under this thesis, the student will learn and understand how to build such a prototypical smart sensing system from scratch, i.e. by depositing, patterning and stacking ultra-thin (~nm) oxide and metal films into the simple sensor and memristor devices and arranging these building blocks into functional sensing neural network matrices on a chip. The expertise acquired will cover nano-fabrication methods with a focus on atomic layer deposition (ALD), material analyses and electrical characterisation techniques, and an understanding of the hardware neural networks based on emerging devices.
    The thesis will be a part of a wider project, and the student will become a part of our research team. We are looking for creative and dedicated team players, prior experience in related areas is a plus.
  • Theme: Technology and characterization of vertical switching  GaN transistors
    Supervisor: Ing. J. Kuzmík, DrSc.  ( Department of III-V Semiconductors )
    Co-advisors: RNDr. Dagmar Gregušová, DrSc, Mgr. Peter Šichman
    Abstract:
    Massive deployment of III-N based switching transistors promises huge world-wide energy savings. This anticipation stems from material parameters of III-N semiconductors. Consequently, III-N based transistors show extremely efficient switching performance, high robustness and temperature stability. PhD thesis will be focused on proposal, technology and analysis of normally-off vertical transistors from point of view electrical performance, safe switching performance and power maximization. Emphasize will be given to physical analyzes and technological preparation of transistors with highly positive threshold voltage as generally required by industry. Work will represent a continuation of collaboration with partners within ongoing V4-Japan project. Collaboration with partners from Taiwan is anticipated.
  • Theme: III-N quantum structures for new generation of fast tranzistors and logic circuits
    Supervisor: Ing. J. Kuzmík, DrSc.  ( Department of III-V Semiconductors )
    Co-advisors: Ing. Milan Ťapajna, PhD, Ing. Ondrej Pohorelec
    Abstract:
    Goal of the work will be proposal, processing and characterization of quantum well structures for a new generation ultra-fast electronics. Strongly polar material system based on III-N semiconductors containing In(Al)N will be exploited. Properties of transistors will be studied as a function of used substrate (sapphire, SiC, homoepitaxy on GaN), selected processing of the gate contact (Schottky contact versus MOS), and for various threshold voltage value (normally-on mode versus normally-off).  Work will be a part of EU projects Nanomat and Agami_Eurigami.
  • Theme: Study of transport properties of Ga2O3 transistors for applications in kV range
    Supervisor: Ing. Milan Ťapajna, PhD,  ( Department of III-V Semiconductors )
    Abstract:
    Current electronic power device market is mostly covered by Si (<1kV voltage range) and SiC and GaN (up to several kV) devices. At present, however, there are practically no semiconductor power devices available for and above the 10-kV range. Gallium oxide (Ga2O3) is a promising ultra-wide bandgap (Eg=4.8–5.3 eV) semiconductor material, which offers technological potential for design of new electronic devices capable of handling this voltage range. Such devices can enable development of systems for transportation utilising electric drive (cars, trains, ships, aircrafts) or transformation for high-voltage DC power distribution networks. Currently, great research effort is focused on growth of Ga2O3 and development of related electronic devices for power applications. The aim of this work will be the preparation and detailed characterization of transistors based on Ga2O3 layers prepared by chemical vapor deposition (CVD) methods available at the Institute of Electrical Engineering SAS. The main focus will be on studying the transport and structural properties of the prepared Ga2O3 epitaxial layers to achieve high charge carrier mobility. Ga2O3 layers with different crystalline structure and various impurities will be studied. Based on the obtained knowledge, the preparation of Ga2O3 transistors and their detailed electrical characterization will be performed. The electrical breakdown mechanism of the prepared devices will also be analyzed.
  • Theme: The radiation hardness study of ionizing detectors based on SiC and diamond
    Supervisor: Mgr. Bohumír Zaťko, PhD. (Department of Microelectronics and Sensors )
    Abstract:
    The aim of the thesis is the technology preparation of ionizing detectors, study of electrical and detection properties and the influence of radiation dose on its performance. Used detection materials are high-quality epitaxial layer of 4H-SiC, polycrystalline and single crystalline diamond layer. At first the work will be concentrated on design and preparation of detection structures based on the Schottky contacts. Following the electrical characterization (current-voltage, capacity-voltage measurements at various temperatures) will be realized. SiC and diamond are wide band gap materials able to work also at increased temperatures. Selected suitable detection structure will be connected to low noise spectrometric set-up and evaluated at room and also elevated temperatures. Following structures will be irradiated by high doses of radiation based on electrons, protons or neutrons and investigated its properties after irradiation process. Finally, the radiation hardness will be evaluated and compared with standardly used silicon detectors.
    Oddelenie OMS rieši viacero APVV projektov a tiež VEGA projektov zameraných na prípravu a skúmanie detektorov ionizujúceho žiarenia na báze rôznych typov polovodičov, 2D TMD materiálov (MoS2, PtSe2 a iné), supravodivých, feromagnetických oxidových vrstiev, diamantových vrstiev a ich heteroštruktúr.

“Physical Engineering”

  • Theme: Large-scale fabrication and characterization of 2D materials
    Supervisor:  Ing. Marián Varga, PhD.   (Department of Microelectronics and Sensors )
    Abstract:
    Two-dimensional (2D) materials, including transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) or platinum diselenide (PtSe2), are one of the promising materials and a gateway to modern technologies and optoelectronics. Currently, there is a lot of research that studies fabrication of TMDs by chemical vapour deposition (CVD), which makes the use of these 2D materials in the electronic market feasible. The use of alternative methods such as pulsed laser deposition (PLD) also opens up new possibilities in this field and can provide comparative results to elucidate the growth optimization. The available CVD and PLD systems in IEE SAS will be used to study the fundamental aspect of the growth and properties of TMD materials. For research-related activities, the optimized TMD layers are typically grown on standard 1×1 cm2 substrates. However, from a technological point of view, upscaling the fabrication process is a big challenge. Many times, the deposition conditions (temperature, gas flow, pressure, power, etc.) used for small-scale samples preparation may not work well on a larger scale. Thus, the study and optimization of large-scale (4-inch) fabrication will be a new chapter in this interesting field of 2D materials research. The PhD thesis will be focused mainly on the development of technological procedures for the preparation of precisely defined, homogeneous and reproducible TMD layers on large areas using a newly installed two-zone furnace. In addition, a comprehensive characterization of the surface and bulk properties (including morphological, chemical, optical and opto-electronic properties) of the fabricated 2D materials is also expected.
  • Theme: Utilisation of machine learning tools in design of superconducting devices
    Supervisor: Mgr. Mykola Soloviov PhD. ( Department of Superconductor Physics )
    Co-advisors: doc. Ing. Fedor Gömöry, DrSc.
    Abstract:
    Traditionally, the design of a superconducting magnet or a transmission cable consists in the distribution of conductors in several layers, within each the conductors are distributed uniformly. Due to the resent advances in 3D printing, it is nowadays possible to follow the concept of attributing the position for each individual conductor. This however requires a preceding search for the configuration optimal from the point of view of some selected utility parameter, e.g. the generated magnetic field or the cost of operation, or its combination. Pursuit for the optimal configuration, based on the intuition and experience of designer, is limited to the cases when the total number of conductors does not exceed several tens. Utilization of the machine learning procedures, experiencing currently dramatic progress, should allow to optimise the design of superconducting devices containing hundreds or thousands of conductors.
    Task of the student will consist in implementing a machine learning procedure into the design of a racetrack magnet containing 100 high-temperature REBCO conductors, as well as in the design of a power transmission cable consisting of at least 20 conductors. In the initial stage, the procedures allowing fast evaluation of properties of the training configurations, and also a selection of the suitable machine learning process, will take place. Based on preliminary discussion with the colleagues from the FEI STU, involvement of the experts working in the field of artificial intelligence is foreseen. Goal of the research is the assessment of suitability of machine learning procedure to provide the design that compared to the reference created in traditional way would exhibit improvement of some device properties.
    The PhD research could form part of our contribution to the HorizonEurope project “SCARLET” (duration until 02/2027) from which also some expenses could be covered.
  • Theme: Electrical transport in thin layers of some TMDC materials
    Supervisor: Dr. rer. nat. Martin Hulman (Department of Physics and Technology at Nanoscale)
    Abstract:
    In the last two decades, materials characterised by significant dimensional anisotropy represent one of the most studied materials in solid-state physics and materials research. This group also includes transition metal dichalcogenides (TMDC) – compounds of elements S, Se and Te with metals such as Mo, W and Pt. Substances with the chemical formula MX2 can be prepared in very thin layers, which, in the ultimate case, have a thickness of only one unit cell. In that case, we can talk about a genuinely two-dimensional system.
    At the Institute of Electrical Engineering, a group deals with the growth of thin layers of TMDC materials and their characterisation. The dissertation would complement the activities of this group. The topic of the dissertation is the investigation of electrical transport properties of (ultra)thin layers of TMDC materials, specifically, that subgroup of materials with a semi-metallic and metallic character. The work has an experimental nature. It also partially includes the growth of thin layers, but the work focuses on measuring transport characteristics. Besides the transport characterisation, the influence of temperature, doping and structure on the conductivity of 2D materials will be investigated. The dissertation also aims to identify possible “exotic” electronic states in TMDC materials, such as superconductivity or charge density waves.
    The student will work with vacuum and low-temperature facilities during the dissertation. The experimental results will be analysed in terms of different models of solid-state physics. During the dissertation, the presentation of the results at domestic and international conferences is expected, so a good knowledge of spoken and written English is necessary.
  • Theme: Optimizing the fabrication of few-layer structures of 2D materials for use in electronics and advanced sensors
    Supervisor: Mgr. M. Sojková, PhD. (Department of Microelectronics and Sensors )
    Co-advisors: RNDr. Dagmar Gregušová, DrSc.
    Abstract:
    The miniaturization of electronic components is currently reaching its limits, and therefore much attention is paid to the research of new semiconductor materials. One possibility is the use of 2D materials, i.e. materials that are made up of only one layer of atoms. In particular, transition metal dichalcogenides (TMDs) with the general formula MX2, where M is a transition metal (e.g., Mo, W, Pt) and X is a chalcogen (S, Se, or Te), have attracted much attention due to their layered structure and semiconducting properties. These layered materials exhibit interesting electrical and optical properties depending on the number of layers. Thanks to this, 2D TMD materials are suitable for various applications, such as field effect transistors (FET), photodetectors, photovoltaic cells, light emitting diodes or catalysts.
    The work will be focused on optimizing the fabrication of electronic devices (mainly field-controlled transistors) using few-layer films of various types of 2D TMD materials (PtSe2, PtS2, GaS). A two-step method will be used to prepare ultrathin layers, in which thin layers of metals or their oxides are first deposited. In the second step, these layers are annealed in the presence of sulfur or selenium vapors (so-called sulfurization / selenization). Electronic components will be prepared using different methods. We will study the influence of structure fabrication parameters on the properties and functionality of the prepared structures. Optimizing contacts will also be important. The prepared structures will be investigated using X-ray diffraction analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, optical measurements, measurements of electrical properties and other analyses.The work will be carried out at the Institute of Electrical Engineering SAS, which has the necessary technological and characterization equipment. The PhD student will acquire universal skills with a variety of experimental methods and will be actively involved in several projects.

“Physics of Condensed Matter and Acoustics”

  • Theme: Electrical transport in thin layers of some TMDC materials
    Supervisor: Dr. rer. nat. Martin Hulman (Department of Physics and Technology at Nanoscale)
    Abstract:
    In the last two decades, materials characterised by significant dimensional anisotropy represent one of the most studied materials in solid-state physics and materials research. This group also includes transition metal dichalcogenides (TMDC) – compounds of elements S, Se and Te with metals such as Mo, W and Pt. Substances with the chemical formula MX2 can be prepared in very thin layers, which, in the ultimate case, have a thickness of only one unit cell. In that case, we can talk about a genuinely two-dimensional system.
    At the Institute of Electrical Engineering, a group deals with the growth of thin layers of TMDC materials and their characterisation. The dissertation would complement the activities of this group. The topic of the dissertation is the investigation of electrical transport properties of (ultra)thin layers of TMDC materials, specifically, that subgroup of materials with a semi-metallic and metallic character. The work has an experimental nature. It also partially includes the growth of thin layers, but the work focuses on measuring transport characteristics. Besides the transport characterisation, the influence of temperature, doping and structure on the conductivity of 2D materials will be investigated. The dissertation also aims to identify possible “exotic” electronic states in TMDC materials, such as superconductivity or charge density waves.
    The student will work with vacuum and low-temperature facilities during the dissertation. The experimental results will be analysed in terms of different models of solid-state physics. During the dissertation, the presentation of the results at domestic and international conferences is expected, so a good knowledge of spoken and written English is necessary.