Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 38: Phase change/ resistive switching

DS 38.5: Talk

Thursday, March 19, 2015, 16:00–16:15, H 0111

Static and dynamic THz spectroscopy of epitaxially grown GeTe-Sb₂Te₃ alloys — •Valeria Bragaglia¹, Karsten Holldack², and Raffaella Calarco¹ — ¹Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany — ²Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany

In the last few years, the number of investigations on the dynamics of photo induced effects in GeTe-Sb₂Te₃ alloys increased. Full optical measurements were mostly employed in order to get information on both, the electronic and structural response upon excitation. The films investigated are typically grown by sputtering and result in a polycrystalline structure [1].

In our study we focus on epitaxially grown GST which presents a high degree of structural quality. Static measurements where performed in transmittance and reflectance configuration on crystalline and amorphous GST employing Fourier transform Infrared spectroscopy (THz) which allows to access the spectral range of 20-700 cm⁻¹. Epitaxial crystalline GST shows both free carrier and phonon absorption contributions. In particular, employing a multilayer structure model, we conclude that a Drude model convolved with several Lorentzian contributions arising from soft phonon modes simulate well the experimental data. Ultrafast dynamic measurements of amorphous and crystalline GST under laser excitation are ongoing employing 800 nm fs-laser pump and ps-THz probe in the same spectral range in order to investigate time resolved electronic response upon excitation.

[1] M.J. Shu et al., Appl. Phys. Lett. 102, 201903 (2013).