Petr Němec, Alain Moréac, Virginie Nazabal, Martin Pavlišta, Jan Přikryl, Miloslav Frumar

Ge-Sb-Te thin films deposited by pulsed laser: An ellipsometry and Raman scattering spectroscopy study

Journal of Applied Physics 106 (2009) 103509

Pulsed laser (532 nm) deposited Ge₂Sb₂Te₅ thin films were investigated by means of spectroscopic ellipsometry and Raman scattering spectroscopy. Tauc-Lorentz and Cody-Lorentz models were employed for the evaluation of optical functions of thin films in as-deposited (amorphous) and crystalline (cubic) phases. The models' parameters (Lorentz oscillator amplitude, resonance energy, oscillator width, optical band gap, and Urbach energy) calculated for amorphous and crystalline states are discussed. The vibrational modes observed in Raman spectra of amorphous layers are attributed to GeTe_4-nGe_n (n=1, 2, eventually 0) tetrahedra connected by corners (partly by edges) and SbTe₃ units. The Raman spectra of crystalline thin films suggest that the local bonding arrangement around Ge atoms changes; GeTe component is thus mainly responsible for the phase transition in Ge₂Sb₂Te₅ alloys.

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1. Franta D., Hrdlička M., Nečas D., Frumar M., Ohlídal I., Pavlišta M.,
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