Surface physics, thin films

The effect of the thickness of a single-crystal SrTiO$_3$ film on its structure and dielectric parameters in the range of 0.3–1.5 THz

A. V. Pavlenko^ab, N. A. Nikolaev^c, D. V. Stryukov^a, A. A. Rybak^c, V. A. Bobylev<sup>b

a</sup> Southern Research Center of the Russian Academy of Sciences, Rostov-on-Don
^b Southern Federal University, Rostov-on-Don
^c Institute of Automation and Electrometry, Siberian Branch of Russian Academy of Sciences, Novosibirsk

Abstract: Single-crystal thin films of strontium titanate (SrTiO$_3$, STO) of various thicknesses $(h)$: 60 nm, 120 nm and 270 nm were grown on Al$_2$O$_3$(001) substrates using the RF sputtering method. Using X-ray diffraction analysis, it is shown that all STO films are characterized by a pseudo-cubic cell, and have the same deformation of the unit cell. Using the method of pulsed terahertz spectroscopy, it is shown that in the frequency range 0.3–1.5 THz, films are characterized by practically no dispersion of the real $(\varepsilon')$ and imaginary $(\varepsilon'')$ parts of the dielectric constant, but as $h$ decreases, there is a significant increase in $\varepsilon'$ at comparable $\varepsilon''$.

Keywords: thin films, dielectric characteristics, heteroepitaxy, STO, pulsed terahertz spectroscopy.

Received: 01.10.2024
Revised: 20.10.2024
Accepted: 09.03.2025

DOI: 10.61011/FTT.2025.03.60267.249

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