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XRD pattern of the KTO thin film deposited on (0001) sapphire. Peaks of the substrate are denoted as S. All other peaks correspond to the perovskite KTaO3 phase.8 Plain-view FE-SEM micrograph of the film is shown in the inset.
(Color online) (a) THz time-domain wave forms measured at 20 K with a bare sapphire substrate and with a 200 nm thick KTO film deposited on the substrate; 0: direct pass, 1: first internal Fabry-Pérot reflection. (b) Spectra of complex refractive index obtained from the direct pass (closed symbols) and from the first echo (open symbols). Thicknesses of the two substrates differ by 2.3 μm (left plot) and 0 μm (right plot).
(Color online) (a) Real and (b) imaginary part of the permittivity of KTO film for selected temperatures; symbols: experiment, lines: fits using Eq. (1). Microwave permittivity at 16 GHz is also shown in (a).
(a) Soft mode frequency ω0 and relaxation strength g as a function of temperature obtained from the fits of THz spectra. (b) Real part of the permittivity at 16 GHz.
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