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Updated: May 30, 2026
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Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition
Published on: July 26, 2016
Ultrathin SrTiO(3) films: epitaxy and optical properties
M Tyunina1, J Narkilahti, J Levoska
1Microelectronics and Materials Physics Laboratories, University of Oulu, PL4500, FI-90014 Oulun yliopisto, Finland.
Summary
Ultrathin strontium titanate (SrTiO(3)) films exhibit altered optical properties due to their small thickness and biaxial strain. Surface effects dominate visible light absorption, while strain and thickness impact interband transitions.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Thin Film Technology
Background:
- Strontium titanate (SrTiO(3)) is a perovskite oxide with significant dielectric and optical properties.
- Ultrathin films present unique physical characteristics compared to bulk materials.
- Strain engineering is a key method for tuning material properties.
Purpose of the Study:
- To investigate the structural and optical properties of ultrathin SrTiO(3) films.
- To understand the influence of substrate-induced strain and film thickness on SrTiO(3) optical behavior.
- To correlate microstructure with optical response in epitaxial SrTiO(3) films.
Main Methods:
- Pulsed laser deposition (PLD) for growing ultrathin SrTiO(3) films (12-15 nm).
- X-ray diffraction (XRD) for analyzing crystal structure, orientation, and strain.
- Ellipsometric spectroscopy (1-6 eV) for determining room-temperature optical properties.
Main Results:
- Epitaxial growth with biaxial in-plane strain achieved on LaAlO(3), DyScO(3), and KTaO(3) substrates.
- Critical thickness for pseudomorphic growth found to be less than 10 nm, with abrupt strain relaxation observed.
- Optical properties show suppression and smearing of interband transitions due to thickness and strain; surface effects are dominant in the visible range.
Conclusions:
- Strain-induced polarization can increase band gap energies in ultrathin SrTiO(3) films.
- The absorption edge is a complex function of surface effects, film thickness, biaxial strain, and polarization.
- Ultrathin SrTiO(3) films exhibit significantly modified optical properties compared to bulk, offering potential for tailored optoelectronic applications.
