Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5

Hada, Masaki; Oba, Wataru; Kuwahara, Masashi; Katayama, Ikufumi; Saiki, Takanao; Takeda, Jun; Nakamura, Kazutaka G.

doi:10.1038/srep13530

Cited by 38 publications

(44 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Another possibility of phase transition is melting of the GST lattice due to lattice heating caused by the transfer of electron energy to the covalent backbone by applying an ultrashort laser pulse 14 . Moreover, a non-thermal amorphization process caused by displacements of Ge atoms from octahedral to tetrahedral sites induced by ultrashort laser pulses was also reported recently 30 .…”

Section: Resultsmentioning

confidence: 76%

Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

Sun

Ehrhardt

Lotnyk

et al. 2016

Sci Rep

View full text Add to dashboard Cite

The amorphous to crystalline phase transformation of Ge2Sb2Te5 (GST) films by UV nanosecond (ns) and femtosecond (fs) single laser pulse irradiation at the same wavelength is compared. Detailed structural information about the phase transformation is collected by x-ray diffraction and high resolution transmission electron microscopy (TEM). The threshold fluences to induce crystallization are determined for both pulse lengths. A large difference between ns and fs pulse irradiation was found regarding the grain size distribution and morphology of the crystallized films. For fs single pulse irradiated GST thin films, columnar grains with a diameter of 20 to 60 nm were obtained as evidenced by cross-sectional TEM analysis. The local atomic arrangement was investigated by high-resolution Cs-corrected scanning TEM. Neither tetrahedral nor off-octahedral positions of Ge-atoms could be observed in the largely defect-free grains. A high optical reflectivity contrast (~25%) between amorphous and completely crystallized GST films was achieved by fs laser irradiation induced at fluences between 13 and 16 mJ/cm2 and by ns laser irradiation induced at fluences between 67 and 130 mJ/cm2. Finally, the fluence dependent increase of the reflectivity is discussed in terms of each photon involved into the crystallization process for ns and fs pulses, respectively.

show abstract

Section: Resultsmentioning

confidence: 76%

Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

Sun

Ehrhardt

Lotnyk

et al. 2016

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Electron diffraction measurements 32,35,36 were performed in transmission mode on an ~60-nm-thick film of azobenzene molecules. Figure 3a shows the electron diffraction pattern from the film at 52 °C, and sixfold symmetric first-order diffraction peaks are present.…”

Section: Resultsmentioning

confidence: 99%

“…The experimental setup of the compact DC-accelerated electron diffraction system is provided elsewhere 32,35 . UV pulses were focused on the sample film.…”

Section: Methodsmentioning

confidence: 99%

Ultrafast isomerization-induced cooperative motions to higher molecular orientation in smectic liquid-crystalline azobenzene molecules

et al. 2019

Self Cite

View full text Add to dashboard Cite

The photoisomerization of molecules is widely used to control the structure of soft matter in both natural and synthetic systems. However, the structural dynamics of the molecules during isomerization and their subsequent response are difficult to elucidate due to their complex and ultrafast nature. Herein, we describe the ultrafast formation of higher-orientation of liquid-crystalline (LC) azobenzene molecules via linearly polarized ultraviolet light (UV) using ultrafast time-resolved electron diffraction. The ultrafast orientation is caused by the trans-to-cis isomerization of the azobenzene molecules. Our observations are consistent with simplified molecular dynamics calculations that revealed that the molecules are aligned with the laser polarization axis by their cooperative motion after photoisomerization. This insight advances the fundamental chemistry of photoresponsive molecules in soft matter as well as their ultrafast photomechanical applications.

show abstract

“…So, ultrafast switching behavior relying on nonthermal phase transitions in GST superlattices, triggered by an ultrashort laser pulse, has been proposed in refs. [5,6]. Nevertheless, the understanding of certain material properties and physical mechanisms of PCMs, as well as developments based upon them, broadens the perspective for future applications.…”

Section: Introductionmentioning

confidence: 99%

Specific Features of Formation of Laser‐Induced Periodic Surface Structures on Ge₂Sb₂Te₅ Amorphous Thin Films under Illumination by Femtosecond Laser Pulses

Kozyukhin

Smayev

Сигаев

et al. 2020

Physica Status Solidi (b)

View full text Add to dashboard Cite

This article presents the results of irradiation treatment by the 180 fs laser pulses at the wavelength of 1030 nm of Ge2Sb2Te5 amorphous thin films. It is shown that high‐quality laser‐induced periodic surface structures (LIPSS) are formed at certain parameters of irradiation with a period corresponding to the laser wavelength. A distinctive feature of the observed LIPSS is the alternation of amorphous and crystalline regions corresponding to the ridges and valleys of the periodic structures which are perpendicular to the polarization of the femtosecond light beam. These surface crystalline–amorphous alternating structures are characterized by significantly less pronounced surface relief than for previously observed LIPSS formed by femtosecond laser pulses at the wavelength of 515 nm. Possible mechanisms are considered for the LIPSS formation including the formation of surface plasmon polariton and its subsequent interference with the incident beam resulting in spatial modulation of the temperature on the film surface. As the results indicate, the formation of alternating structure has a threshold nature with the threshold laser fluence for LIPSS formation depending logarithmically on the number of laser pulses, which is attributed to the transient nature of the crystallization process.

show abstract

Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5

Cited by 38 publications

References 45 publications

Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

Ultrafast isomerization-induced cooperative motions to higher molecular orientation in smectic liquid-crystalline azobenzene molecules

Specific Features of Formation of Laser‐Induced Periodic Surface Structures on Ge₂Sb₂Te₅ Amorphous Thin Films under Illumination by Femtosecond Laser Pulses

Contact Info

Product

Resources

About

Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5

Cited by 38 publications

References 45 publications

Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

Ultrafast isomerization-induced cooperative motions to higher molecular orientation in smectic liquid-crystalline azobenzene molecules

Specific Features of Formation of Laser‐Induced Periodic Surface Structures on Ge2Sb2Te5 Amorphous Thin Films under Illumination by Femtosecond Laser Pulses

Contact Info

Product

Resources

About

Specific Features of Formation of Laser‐Induced Periodic Surface Structures on Ge₂Sb₂Te₅ Amorphous Thin Films under Illumination by Femtosecond Laser Pulses