Stylianidis, Evgenios;
(2025)
Structural and electrical properties of strontium titanate-based heterostructures.
Doctoral thesis (Ph.D), UCL (University College London).
Abstract
Strontium titanate is a special material to condensed matter physicists and keeps fascinating with its intriguing richness of physical properties. Despite being an incipient ferroelectric in its pure form with a subtle transition to a tetragonal antiferrodistortive phase at low temperatures, it displays a great sensitivity to external perturbations, be it high electric fields, mechanical stress or chemical impurities. Calculations based on phenomenological theory and first-principles predict that biaxial strain induces a rich phase diagram with multiple ferroelectric and antiferrodistortive phases stabilized at elevated temperatures. After more than 20 years of experimental studies on the topic, the effect of biaxial strain on strontium titanate thin films is yet not-well understood. This thesis explores the structural and electrical properties of strained epitaxial strontium titanate thin films and heterostructures. We use off-axis radiofrequency magnetron sputtering to grow epitaxial SrTiO3 thin films on lattice-mismatched substrates, across a wide range of biaxial strain that extends from −3% to +2%. We employ a range of advanced experimental tech- niques - including laboratory and synchrotron-based X-ray diffraction, scanning probe microscopies, impedance spectroscopy and others - to explore the structural and electrical properties of the strained films, aiming to understand the effect of biaxial strain on the antiferrodistortive and ferroelectric phases of strained SrTiO3. With our studies we hope to shed light and bring some new insights on the properties of this important material. Importantly, we extend the experimental phase diagram of SrTiO3 to higher strains. Moreover, our results highlight the role played by non-equilibrium phenomena when studying the electrical properties of dielectric or ferroelectric capacitors
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Structural and electrical properties of strontium titanate-based heterostructures |
| Language: | English |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10207504 |
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