Atomic-scale imaging of ultrafast materials dynamics

Flannigan, David J.; Lindenberg, Aaron M.

doi:10.1557/mrs.2018.146

Cited by 10 publications

(3 citation statements)

References 40 publications

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“…There are a few reviews on the instrumentation, working principles, and applications of S-UEM and T-UEM, which were recently provided by Mohammed, , Kwon, Liao, Flannigan, and Ischenko et al In this feature article, we will present the latest developments in the experimental setup and data interpretation and provide a comprehensive summary of crucial and emerging applications and further future development of S-UEM.…”

Section: Introductionmentioning

confidence: 99%

Access to Ultrafast Surface and Interface Carrier Dynamics Simultaneously in Space and Time

et al. 2021

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Charge carrier dynamics at material surfaces and interfaces play a fundamental role in controlling the performance of photocatalytic reactions and photovoltaic devices; however, precise characterization of the surface dynamical properties of a material with nanometer (nm) and femtosecond (fs) spatial and temporal resolutions, respectively, is a precondition for profound understanding and is thus urgently needed. Many techniques have been developed to meet this demand, but barely any of them have simultaneous excellent surface sensitivity (depth resolution) and sufficient spatiotemporal resolutions, except for a one-of-a-kind second-generation scanning ultrafast electron microscope (S-UEM), which has been established and developed at KAUST to provide direct and controllable dynamical information about the ultrafast charge carrier dynamics and the localization of electrons and holes on the photoactive material surface and interfaces. In this feature article, the instrumentation, working principles, new capabilities, and unique applications of S-UEM in the ultrafast characterization of material surfaces and interfaces, including charge carrier injection, surface carrier diffusion, surface carrier trapping, and recombination, are systematically summarized and inspected. Future developments from both theoretical and experimental perspectives are also discussed.

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Section: Introductionmentioning

confidence: 99%

Access to Ultrafast Surface and Interface Carrier Dynamics Simultaneously in Space and Time

et al. 2021

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“…As a result, transient signals are convolved together with electronic processes including electron–electron and electron–interface scattering, making the interpretation of the lattice response rather complicated. In contrast, transient atomic structure probing, which can be achieved using pulsed X-ray , or electron-beam − sources, provides direct access into the nonequilibrium thermodynamic processes as reflected in the photoinduced structural responses, which have not been studied in colloidal gold NCs before.…”

mentioning

confidence: 99%

Nonequilibrium Thermodynamics of Colloidal Gold Nanocrystals Monitored by Ultrafast Electron Diffraction and Optical Scattering Microscopy

Guzelturk,

Utterback,

Coropceanu

et al. 2020

ACS Nano

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Metal nanocrystals exhibit important optoelectronic and photocatalytic functionalities in response to light. These dynamic energy conversion processes have been commonly studied by transient optical probes to date, but an understanding of the atomistic response following photoexcitation has remained elusive. Here, we use femtosecond resolution electron diffraction to investigate transient lattice responses in optically excited colloidal gold nanocrystals, revealing the effects of nanocrystal size and surface ligands on the electron–phonon coupling and thermal relaxation dynamics. First, we uncover a strong size effect on the electron–phonon coupling, which arises from reduced dielectric screening at the nanocrystal surfaces and prevails independent of the optical excitation mechanism (i.e., inter- and intraband). Second, we find that surface ligands act as a tuning parameter for hot carrier cooling. Particularly, gold nanocrystals with thiol-based ligands show significantly slower carrier cooling as compared to amine-based ligands under intraband optical excitation due to electronic coupling at the nanocrystal/ligand interfaces. Finally, we spatiotemporally resolve thermal transport and heat dissipation in photoexcited nanocrystal films by combining electron diffraction with stroboscopic elastic scattering microscopy. Taken together, we resolve the distinct thermal relaxation time scales ranging from 1 ps to 100 ns associated with the multiple interfaces through which heat flows at the nanoscale. Our findings provide insights into optimization of gold nanocrystals and their thin films for photocatalysis and thermoelectric applications.

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“…Since the introduction of laser-triggered photocathodes in electron microscopy the field of single shot 1 and stroboscopic 2 time-resolved electron imaging, diffraction and spectroscopy has resulted in many new insights in physics, chemistry, biology and material science. 3,4 In a recent exciting development in which the flat photo-cathode is replaced by a nano-tip, the peak brightness of pulsed electron beams has become similar to values reported for conventional continuous Schottky field emitters. 5,6 The possibility of performing high-quality electron imaging, diffraction and spectroscopy with nanosecond to femtosecond temporal resolution causes the ultrafast transmission electron microscope (UTEM) to be one of the most powerful research tools to study ultrafast dynamics in the nanoscale world.…”

Section: Introductionmentioning

confidence: 81%

Dual mode microwave deflection cavities for ultrafast electron microscopy

Rens

Verhoeven

Kieft

et al. 2018

Applied Physics Letters

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This paper presents the experimental realization of an ultrafast electron microscope operating at a repetition rate of 75 MHz based on a single compact resonant microwave cavity operating in dual mode. This elliptical cavity supports two orthogonal TM 110 modes with different resonance frequencies that are driven independently. The microwave signals used to drive the two cavity modes are generated from higher harmonics of the same Ti:Sapphire laser oscillator. Therefore the modes are accurately phase-locked, resulting in periodic transverse deflection of electrons described by a Lissajous pattern. By sending the periodically deflected beam through an aperture, ultrashort electron pulses are created at a repetition rate of 75 MHz. Electron pulses with τ = (750 ± 10) fs pulse duration are created with only (2.4 ± 0.1) W of microwave input power; with normalized rms emittances of n,x = (2.1 ± 0.2) pm rad and n,y = (1.3 ± 0.2) pm rad for a peak current of I p = (0.4 ± 0.1) nA. This corresponds to an rms normalized peak brightness of B np,rms = (7 ± 1) × 10 6 A/m 2 sr V, equal to previous measurements for the continuous beam. In addition, the FWHM energy spread of ∆U = (0.90 ± 0.05) eV is also unaffected by the dual mode cavity. This allows for ultrafast pump-probe experiments at the same spatial resolution of the original TEM in which a 75 MHz Ti:Sapphire oscillator can be used for exciting the sample. Moreover, the dual mode cavity can be used as a streak camera or time-of-flight EELS detector with a dynamic range > 10 4 .

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Atomic-scale imaging of ultrafast materials dynamics

Abstract: Abstract

Cited by 10 publications

References 40 publications

Access to Ultrafast Surface and Interface Carrier Dynamics Simultaneously in Space and Time

Access to Ultrafast Surface and Interface Carrier Dynamics Simultaneously in Space and Time

Nonequilibrium Thermodynamics of Colloidal Gold Nanocrystals Monitored by Ultrafast Electron Diffraction and Optical Scattering Microscopy

Dual mode microwave deflection cavities for ultrafast electron microscopy

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