Femtosecond Studies of Image-Potential Dynamics in Metals

Schoenlein, R. W.; Fujimoto, James G.; Eesley, G. L.; Capehart, T. W.

doi:10.1103/physrevlett.61.2596

Cited by 174 publications

(87 citation statements)

References 15 publications

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“…Laser pulses of a few femtoseconds duration can be generated conveniently with Ti:sapphire lasers [209][210][211] and the time delay between two laser pulses can be controlled with sub-femtosecond resolution [212]. Two-photon photoemission is the method of choice to study the decay of electronic excitations at surfaces directly in the time domain [35,[213][214][215]. The excitation scheme of the two-photon photoemission process is shown in Fig.…”

Section: Two-photon Photoemissionmentioning

confidence: 99%

“…The topographical images monitor simultaneously the quality and structures of the surface area under investigation. Two-photon photoemission (2PPE) [4,34] in the time-resolved mode is the only technique which is able to study the decay in the time domain [35,36]. By combining this information with spectroscopic measurements a very detailed picture of the electron dynamics emerges.…”

Section: Introductionmentioning

confidence: 99%

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Decay of electronic excitations at metal surfaces

Echenique

Berndt

Chulkov

et al. 2004

Surface Science Reports

438

403

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Section: Two-photon Photoemissionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Decay of electronic excitations at metal surfaces

Echenique

Berndt

Chulkov

et al. 2004

Surface Science Reports

438

403

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“…This technique can probe carrier dynamics in real-time and allows to access a wider energy range than typical transport studies. Time-resolved photoemission was developed from twophoton-photoemission [19,20] and has become a powerful technique for studies of surface and bulk electron dynamics on the femtosecond time-scale [21,22,23,24,25,26,27,28]. It has been most frequently used to probe the relaxation of photoexcited electrons with energies ranging from a few hundred meV above the Fermi level up to the vacuum level.…”

mentioning

confidence: 99%

Charge-carrier dynamics in single-wall carbon nanotube bundles: a time-domain study

Hertel

Fasel

Moos

2002

Applied Physics A: Materials Science & Processing

114

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Abstract. We present a real-time investigation of ultrafast carrier dynamics in single-wall carbon nanotube bundles using femtosecond time-resolved photoelectron spectroscopy. The experiments allow to study the processes governing the subpicosecond and the picosecond dynamics of non-equilibrium charge-carriers. On the subpicoseond timescale the dynamics are dominated by ultrafast electronelectron scattering processes which lead to internal thermalization of the laser excited electron gas. We find that quasiparticle lifetimes decrease strongly as a function of their energy up to 2.38 eV above the Fermi-level -the highest energy studied experimentally. The subsequent cooling of the laser heated electron gas down to the lattice temperature by electron-phonon interaction occurs on the picosecond time-scale and allows to determine the electronphonon mass enhancement parameter λ. The latter is found to be over an order of magnitude smaller if compared, for example, with that of a good conductor such as copper.PACS 78.47.+; 81.07.De; 78.67.Ch Carbon nanotubes (CNTs) and in particular single-wall carbon nanotubes (SWNTs) have attracted broad interest due to their unique electronic structure and properties. Among the most impressive demonstrations of their potential use in novel technologies are the fabrication of fieldeffect and single-electron transitors from individual or small bundles of SWNTs [ 1,2,3,4]. Other conceivable applications include the implementation of CNTs as emitters in field-emission displays [5,6], ultrastrong fibers [7,8], chemical sensors [9,10], super-capacitors [11] and more. As molecular field effect transistors they have already been implemented into simple logic devices with outstanding transport characteristics and promising scaling behavior [12]. As molecular wires, carbon nanotubes exhibit exceptional resilience with respect to current induced failure and sustain current densities exceeding 10 9 A/cm 2 before * Corresponding Author suffering fatal damage, as reported by various groups [13,14,15,16,17,18]. The carrier scattering processes governing linear and non-linear transport properties in these devices, such as electron-electron (e-e), electron-phonon (eph) or impurity scattering are most frequently investigated by conventional -i.e. time-independent -transport studies.Here we present a complementary time-domain study of carrier dynamics in bundles of single-wall carbon nanotubes using femtosecond time-resolved photoemission. This technique can probe carrier dynamics in real-time and allows to access a wider energy range than typical transport studies. Time-resolved photoemission was developed from twophoton-photoemission [19,20] and has become a powerful technique for studies of surface and bulk electron dynamics on the femtosecond time-scale [21,22,23,24,25,26,27,28]. It has been most frequently used to probe the relaxation of photoexcited electrons with energies ranging from a few hundred meV above the Fermi level up to the vacuum level. Here, we have extended the most commonly us...

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“…Time-resolution was introduced to two-photon photoemission about 15 years ago [77,78]. With the advent of easy to use, high-repetition rate Ti:sapphire lasers the experimental possibilities expanded tremendously.…”

Section: Discussionmentioning

confidence: 99%

Time‐resolved two‐photon photoemission

Fauster¹

2003

Solid‐State Photoemission and Related Methods

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In this chapter time resolution will be introduced to photoemission experiments. This means not just a series of regular photoemission measurements to monitor the changes of a sample with time. In two-photon photoemission the time delay between the two photons is an additional experimental parameter which can be controlled with femtosecond resolution, i.e., on a time scale relevant for electronic processes. At the same time, the introduction of the second photon leads to the participation of an additional electronic state in the energy diagram for photoemission. Energy diagramIn Figure 8.1 the transition from initial state |1 to an intermediate state |2 after the absorption of the photon with energy hν a is shown. The second photon of energy hν b excites the electron out of the intermediate state into the final state |3 . If the final state energy E 3 is above the vacuum energy E vac , the electron might leave the surface and its kinetic energy E kin is measured with an electron energy analyzer. Obviously, the initial state has to be occupied, i.e., its energy E 1 should be below the Fermi energy E F . The intermediate state on the other hand has to be empty at first. In most cases it is desirable to keep the photon energy hν a below the work function Φ = E vac − E F , because this constitutes the threshold for one-photon photoemission. This applies also to the other photon, because processes with the role of the two photons interchanged are possible as well. Energy-resolved spectroscopyThe spectrum sketched at the right of Fig. 8.1 shows a peak at the final state energy E 3 . The cutoff at kinetic energy zero corresponds to the vacuum level E vac of the sample. Electrons with the highest energy after the absorption of the photons with energies hν a and hν b appear at kinetic energy E max − E vac = hν a + hν b − Φ. These limits are familiar from regular photoemission spectroscopy and can be used to determine the work function from the width of the spectrum. Similarly, the momentum k of the electron parallel to the surface is conserved for single-crystal surfaces. For electrons emitted at an angle ϑ with respect to the surface normal one obtainshk = √ 2mE kin sin ϑ. Umklapp processes would add reciprocal lattice vectors of the surface to the momentum conservation, but play usually no role in twophoton photoemission. One has to keep in mind that the kinetic energies are generally quite

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Femtosecond Studies of Image-Potential Dynamics in Metals

Cited by 174 publications

References 15 publications

Decay of electronic excitations at metal surfaces

Decay of electronic excitations at metal surfaces

Charge-carrier dynamics in single-wall carbon nanotube bundles: a time-domain study

Time‐resolved two‐photon photoemission

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