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7ALT'22
LM-I-22
LASER-MATTER INTERACTION
Laser-Induced Phase Transitions Dynamics of GeTe and Ge2Sb2Te5 Thin Films
A.V. Kiselev, A.A. Burtsev, V.V. Ionin, N.N. Eliseev, V.A. Mikhalevsky, A.A. Nevzorov,
M.D. Khomenko and A.A. Lotin
ILITRAS — Branch of FSRC "Crystallography and Photonics " RAS, 140700, Shatura, Svyatoozerskaya Str., 1, Moscow Region, Russia Main author email address: [email protected]
Thin film chalcogenide materials based on germanium telluride (GeTe, Ge2Sb2Te5) are widely used in photonic and optoelectronic devices [1]. These alloys have very small amorphization and crystallization times in the order of nanoseconds, which combined with large cyclability and a pronounced property contrast between the crystalline and amorphous phases [2].
In this paper, the dynamics of changes in the optical transmission and reflection coefficients of thin 100 nm GeTe and Ge2Sb2Te5 films during crystallization and amorphization induced by nano- and femtosecond laser pulses are studied. It is shown that the change in optical coefficients in the subnanosecond time scale during crystallization and amorphi-zation induced by fs pulses is mainly determined by the photoexcitation of charge carriers. On the nano-microsecond time scale, the processes of crystallization and amorphization are determined by thermal processes and described by the mathematical model of thermal conductivity and the Stefan problem. The progress of the phase transition can be monitored using the increase in reflectance upon crystallization and analyzed using the Johnson-Mehl-Avrami-Kolmogorov model [3].
Reproducible multi-level modulation of optical constants of samples is demonstrated. The modulation magnitude is limited by the Booger absorption. Results demonstrate different mechanisms of crystallization for nano- [4-6] and femtosecond laser pulses.
[1] K.V. Sreekanth, M. ElKabbash, V. Caligiuri, R. Singh, A. De Luca, G. Strangi. New Directions in Thin Film Nanophotonics, ch. 3 (2019).
[2] P. Guo, A. M. Sarangan and I. Agha. A Review of Germanium-Antimony-Telluride Phase Change Materials for Non-Volatile Memories and Optical Modulators. Applied Sciences, 9, 3, 530 (2019).
[3] V. Weidenhof, I. Friedrich, S. Ziegler, and M. Wuttig. Laser induced crystallization of amorphous Ge2Sb2Te5 films. Journal of Applied Physics, 89, pp. 3168-3176 (2001).
[4] V. V. Ionin, A. V. Kiselev, N. N. Eliseev, V. A. Mikhalevsky, M. A. Pankov, A. A. Lotin, Multi-level reversible laser-induced phase transitions in GeTe thin films. Applied Physics Letters, 117, 011901 (2020).
[5] A.V. Kiselev, V.A. Mikhalevsky, A.A. Burtsev, V.V. Ionin, N.N. Eliseev, A.A. Lotin, Transmissivity to reflectivity change delay phenomenon observed in GeTe thin films at laser-induced reamorphization, Optics and Laser Technology, 143, 107305 (2021)
[6] A.V. Kiselev, V.V. Ionin, A.A. Burtsev, N.N. Eliseev, V.A. Mikhalevsky, N.A. Arkharova, D.N. Khmelenin and A.A. Lotin, Dynamics of reversible optical properties switching of Ge2Sb2Te5 thin films at laser-induced phase transitions, Optics and Laser Technology, 147 107701 (2022)
