Single Pulse Laser‐Induced Phase Transitions of PLD‐Deposited Ge2Sb2Te5 Films

Lu, Hongbing; Thelander, Erik; Gerlach, Jürgen W.; Decker, Ulrich; Zhu, Benpeng; Rauschenbach, B.

doi:10.1002/adfm.201202665

Cited by 39 publications

(18 citation statements)

References 35 publications

(56 reference statements)

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“…This vast contrast of n between the two structural phases was achieved by a change to the chemical bonding from covalent in the amorphous state to the resonant bonding after being crystallised . By heating the as‐deposited amorphous GST (a‐GST) layer for 30 min at 433 K on a hot plate in a flowing argon atmosphere, the GST layer can be crystallised (c‐GST) …”

Section: Resultsmentioning

confidence: 99%

A High‐Index Ge₂Sb₂Te₅‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation

Cao

Liu

Tang

et al. 2019

Laser & Photonics Reviews

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Third-order harmonic generation (THG) plays a vital role in microscopy, optical communications, etc. Conventional methods of obtaining efficient THG in macroscopic crystals is already mature; however, they will finally limit the miniaturization and integration of on-chip laser sources. To date, THG from either photonic crystals or metamaterials provides compact photonic platforms; however, selection of materials remains elusive. Herein, a giant enhancement of THG efficiency from an air/high index Ge 2 Sb 2 Te 5 (GST)/gold multi-layered Fabry-Perot cavity is experimentally demonstrated. At cavity resonant wavelength in near-infrared regime, the efficiency of THG from a 50-nm thick amorphous GST planar film is boosted 422 times compared to that of nonresonant conditions. Interestingly, the THG efficiency has a dramatic decrease of three orders when the structural state of GST is transformed from amorphous to crystalline. These findings have a potential for achieving an ultracompact nonlinear optical source with high efficiency and switchable functionality.

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Section: Resultsmentioning

confidence: 99%

A High‐Index Ge₂Sb₂Te₅‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation

Cao

Liu

Tang

et al. 2019

Laser & Photonics Reviews

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“…The peaks attributed to the cubic structure have been identified and indexed. The 2 θ position of the (200) peak, which is the most intensive 28 , shifts from 29.2° to 28.3° above the 250 °C due to the phase transformation from cubic to hexagonal phase. From the XRD measurements, we further confirm that the GST films used in field effect measurements exhibit cubic structure.…”

Section: Resultsmentioning

confidence: 99%

Observation of carrier localization in cubic crystalline Ge2Sb2Te5 by field effect measurement

Qian

Tong

et al. 2018

Sci Rep

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The tunable disorder of vacancies upon annealing is an important character of crystalline phase-change material Ge2Sb2Te5 (GST). A variety of resistance states caused by different degrees of disorder can lead to the development of multilevel memory devices, which could bring a revolution to the memory industry by significantly increasing the storage density and inspiring the neuromorphic computing. This work focuses on the study of disorder-induced carrier localization which could result in multiple resistance levels of crystalline GST. To analyze the effect of carrier localization on multiple resistant levels, the intrinsic field effect (the change in surface conductance with an applied transverse electric field) of crystalline GST was measured, in which GST films were annealed at different temperatures. The field effect measurement is an important complement to conventional transport measurement techniques. The field effect mobility was acquired and showed temperature activation, a hallmark of carrier localization. Based on the relationship between field effect mobility and annealing temperature, we demonstrate that the annealing shifts the mobility edge towards the valence-band edge, delocalizing more carriers. The insight of carrier transport in multilevel crystalline states is of fundamental relevance for the development of multilevel phase change data storage.

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“…Coherent light is used in optical switching to induce the phase transformation. Different experimental studies on the property changes of phase-change materials upon nano-, pico- to femtosecond laser pulse irradiation151617181920212223 have been published in the last years. However, comparative examinations are still lacking.…”

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

Sun

Ehrhardt

Lotnyk

et al. 2016

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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.

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Single Pulse Laser‐Induced Phase Transitions of PLD‐Deposited Ge₂Sb₂Te₅ Films

Cited by 39 publications

References 35 publications

A High‐Index Ge₂Sb₂Te₅‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation

A High‐Index Ge₂Sb₂Te₅‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation

Observation of carrier localization in cubic crystalline Ge2Sb2Te5 by field effect measurement

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

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Single Pulse Laser‐Induced Phase Transitions of PLD‐Deposited Ge2Sb2Te5 Films

Cited by 39 publications

References 35 publications

A High‐Index Ge2Sb2Te5‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation

A High‐Index Ge2Sb2Te5‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation

Observation of carrier localization in cubic crystalline Ge2Sb2Te5 by field effect measurement

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

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Single Pulse Laser‐Induced Phase Transitions of PLD‐Deposited Ge₂Sb₂Te₅ Films

A High‐Index Ge₂Sb₂Te₅‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation

A High‐Index Ge₂Sb₂Te₅‐Based Fabry–Perot Cavity and Its Application for Third‐Harmonic Generation