On 2 September 2026 at 14.15 Mahtab Salari Mehr will defend her doctoral thesis “Microstructure optimization of atomic layer deposited chromium-containing ternary compound thin films”.
Supervisors:
Dr. Hugo Mändar, Associate Professor in Materials Science, Institute of Physics, University of Tartu.
Dr. Lauri Aarik, Research Fellow in Materials Science, Institute of Physics, University of Tartu
Dr. Taivo Jõgiaas, Research Fellow in Materials Science, Institute of Physics, University of Tartu
Opponents:
Dr. Per Eklund, Professor in Materials Chemistry, Department of Chemistry, Ångström Laboratory, Uppsala University
Dr. Henrik Pedersen, Professor in Inorganic Chemistry, Department of Physics, Chemistry and Biology, Linköping University
Summary
Chromium oxide is a technologically important material due to its high hardness, wear resistance, corrosion resistance, and thermal stability. These properties make this material useful, for example, in microelectronics, MEMS devices and protective and optical coatings. In order to expand the application range of films and coatings based on binary chromium oxide (Cr-O) and to improve its physicochemical properties, the conversion of the binary material into a ternary material (Cr-Me-O), where oxides of other metals (e.g. Ti, Al, Zr, Cu, Hf) are added to the chromium oxide, is increasingly used. Such multicomponent materials allow changing the microstructure of the films and thereby also the mechanical, optical and thermal stability properties of the film. Since few studies have been conducted on atomic layer deposited (ALD) ultrathin (thickness 10–100 nm) multicomponent oxide films containing chromium, the relationships among the deposition process, composition, microstructure and properties are not yet sufficiently known. This doctoral thesis investigated the relationships between the ALD growth process of various Cr-Me-O type (Me=Ti, Al, Hf) thin films and their physical properties (structure, hardness, elasticity, wear resistance, refractive index, optical absorption, thermal stability). It was determined that Cr-Me-O type films have higher wear resistance, tunable optical properties, and higher thermal stability compared to chromium oxide films. In particular, the thermal stability was increased from about 500 °C for binary chromium oxide to as high as 900 °C for ternary films. Overall, the thesis shows how composition engineering can be used to develop chromium oxide -based thin films with properties better suited for advanced technological applications.
Zoom: doktoritöö kaitsmine (meeting ID: 953 058 8152, passcode: kaitsmine).
