Significant Volume Expansion as a Precursor to Ablation and Micropattern Formation in Phase Change Material Induced by Intense Terahertz Pulses

Abstract

With rapid advances occurring in terahertz (THz) radiation generation techniques, the interaction between matter and intense THz fields has become an important research topic. Among different types of THz radiation sources, the free electron laser (FEL) is a promising experimental tool that is expected to pave the way for new forms of material processing, control of phase transitions, and serve as a test bench for extreme operating conditions in high-speed small-size electrical and magnetic devices through the exploitation of strong THz electrical and magnetic fields without the presence of interband electronic excitation. In the current work, we irradiated Ge2Sb2Te5 phase change memory material with intense THz pulse trains from an FEL and observed THz-induced surface changes due to damage as a precursor to ablation and the formation of fine surface undulations whose spatial period is comparable to or slightly smaller than the wavelength of the excitation THz pulses in the material. The formation of undulations as well as the fact that no significant thermal effect was observed below the volume expansion threshold suggests that THz-induced effects mainly contributed to the observed changes. To the best of our knowledge, this is the first experimental observation of THz-induced undulations (so-called “LIPSS”), which are of potential importance for laser material processing.

Reconfiguration of magnetic domain structures of ErFeO3 by intense terahertz free electron laser pulses

“…From the viewpoint of high-intensity THz light sources, cutting-edge THz free electron lasers (FEL) offer pulse energies of millijoule level, which is several orders of magnitude stronger than what is available with conventional mode-locked Ti:Sapphire amplifier-based THz sources. The extremely high pulse energy contained in THz-FEL is known to enable even destructive phenomena such as desorption of molecules 23,24 and amorphous-crystalline phase transition 5,25,26 , to count a few. In this context, one can expect that the irradiation of such ultrastrong THz-FEL pulses on spin systems could potentially lead to macroscopic change of the magnetization by strongly perturbing critical order parameters such as anisotropy, exchange interactions, and domain wall mobility [27][28][29] .…”

Dynamic Terahertz Plasmonics Enabled by Phase‐Change Materials

“…[142][143][144][145][146][147] In this section, a few pioneering reports about active THz plasmonics based Adv. [142][143][144][145][146][147] In this section, a few pioneering reports about active THz plasmonics based Adv.…”

Terahertz-induced martensitic transformation in partially stabilized zirconia

“…To populate the TA phonon mode that triggers the martensitic transformation, we use a THz-free electron laser (THz-FEL). Recently, amorphous-crystalline phase switching has been demonstrated using this THz source in Ge 2 Sb 2 Te 5 which also exhibits the photoinduced phase transition 21 . Additionally, a high-e ciency elastic wave generation at the surface of water has been reported using the same THz source 22,23 , suggesting that generation of a mechanical force in t-ZrO 2 is possible.…”