Ultrafast electron diffraction at surfaces after laser excitation

Janzen, A.; Krenzer, B.; Zhou, Ping; Linde, D. von der; Hoegen, M. Horn‐von

doi:10.1016/j.susc.2006.02.070

Cited by 43 publications

(37 citation statements)

References 23 publications

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“…21 In previous studies, we investigated the thermal response of a 5.5 nm thin Bi film by means of ultrafast electron diffraction. 22,23 We found good agreement between the measured thermal boundary conductance and the value obtained by using the phonon transmission probability calculated in the two above described models.…”

Section: Introductionsupporting

confidence: 64%

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Thermal response of epitaxial thin Bi films on Si(001) upon femtosecond laser excitation studied by ultrafast electron diffraction

et al. 2008

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The thermal response of epitaxial Bi films deposited on Si͑001͒ upon femtosecond laser pulse excitation is investigated by means of ultrafast electron diffraction. The initial surface temperature increase is caused by linear absorption of 800 nm photons. The exponential decay of the transient film temperature is governed by the thermal boundary conductance of the Bi-Si interface. The decay constant linearly depends on the film thickness and was found between 550 and 1100 ps in the thickness range from 6 to 12.2 nm. The thermal boundary conductance of the Bi-Si interface extracted from the linear dependence yields K = ͑1320Ϯ 60͒ W / ͑cm 2 K͒ in accordance with earlier calculations.

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Section: Introductionsupporting

confidence: 64%

“…22,23,25 Briefly, a short electron pulse is diffracted at a surface for different delays from an initial short laser pulse excitation. Because of the Debye-Waller effect, the diffraction spot intensity is affected by the surface temperature, which is used to extract the transient temperature evolution.…”

Section: Methodsmentioning

confidence: 99%

Thermal response of epitaxial thin Bi films on Si(001) upon femtosecond laser excitation studied by ultrafast electron diffraction

et al. 2008

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“…4 For example, a high density of interfaces can reduce the effective thermal conductivity of materials below the amorphous limit 5,6 and therefore may find applications in improving thermoelectric energy conversion. 7 The acoustic mismatch model (AMM) and diffuse mismatch model (DMM) are often used to predict and interpret the interface thermal conductance G. 8,9 These models assume that G is a consequence of only the lattice dynamics of the bulk materials on each side of the interface; changes in the bonding and vibrational density of states of atoms adjacent to the interface are not explicitly accounted for in these models. In the AMM, the phonon transmission at the interface is derived from differences in acoustic impedances, i.e., products of the mass density and speeds of sound.…”

Section: Introductionmentioning

confidence: 99%

Pressure tuning of the thermal conductance of weak interfaces

et al. 2011

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We use high pressure to reveal the dependence of interfacial heat transport on the stiffness of interfacial bonds. The combination of time-domain thermoreflectance and SiC anvil techniques is used to measure the pressure-dependent thermal conductance G(P ) of clean and modified Al/SiC interfaces at pressures as high as P = 12 GPa. We create low-stiffness, van der Waals-bonded interfaces by transferring a monolayer of graphene onto the SiC surface before depositing the Al film. For such weak interfaces, G(P ) initially increases approximately linearly with P . At high pressures, P > 8 GPa, the thermal conductance of these weak interfaces approaches the high values characteristic of strongly bonded, clean interfaces.

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“…However, direct observation of atomic motion in nanostructures with low atomic number, such as carbon, has not yet been achieved. Electron diffraction, with its five orders of magnitude enhanced scattering cross-section and advanced schemes achieving femtosecond temporal resolution [11,12,13,14], offers a new window into the realm of photo-excited structural dynamics, with sensitivity down to < ∼ 1 nm [11,14,15].…”

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confidence: 99%

Direct Observation of Optically Induced Transient Structures in Graphite Using Ultrafast Electron Crystallography

et al. 2008

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We use ultrafast electron crystallography to study structural changes induced in graphite by a femtosecond laser pulse. At moderate fluences of ≤21 mJ/cm 2 , lattice vibrations are observed to thermalize on a time scale of ≈8 ps. At higher fluences approaching the damage threshold, lattice vibration amplitudes saturate. Following a marked initial contraction, graphite is driven nonthermally into a transient state with sp 3 -like character, forming interlayer bonds. Using ab initio density functional calculations, we trace the governing mechanism back to electronic structure changes following the photo-excitation.

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Ultrafast electron diffraction at surfaces after laser excitation

Cited by 43 publications

References 23 publications

Thermal response of epitaxial thin Bi films on Si(001) upon femtosecond laser excitation studied by ultrafast electron diffraction

Thermal response of epitaxial thin Bi films on Si(001) upon femtosecond laser excitation studied by ultrafast electron diffraction

Pressure tuning of the thermal conductance of weak interfaces

Direct Observation of Optically Induced Transient Structures in Graphite Using Ultrafast Electron Crystallography

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