Ultrafast dynamics of laser-excited electron distributions in silicon

Goldman, Jay R.; Prybyla, J. A.

doi:10.1103/physrevlett.72.1364

Cited by 198 publications

(104 citation statements)

References 13 publications

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“…Characteristic for semi-conducting tubes should be the slow decay of electrons from the bottom of the conduction band. For semiconductors like Si, for example, interband relaxation across the bandgap via phonon emission is slow with decay times typically on the ns timescale [54]. Here we do not observe any decay which might be attributed to interband recombination in semiconducting tubes.…”

Section: Internal Thermalization and E-e Interactionsmentioning

confidence: 53%

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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Section: Internal Thermalization and E-e Interactionsmentioning

confidence: 53%

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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“…5͑a͔͒. Since emission of optical phonons by photocarriers in semiconductors typically occurs on subpicosecond time scales, 25 the slow disappearance of free charges observed here suggests that the rate determining step for exciton formation is acoustic phonon emission. This picture is corroborated by the temperature dependence of the exciton formation rate ͑again investigated through the decay of the real conductivity͒ shown in Fig.…”

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confidence: 64%

Exciton and electron-hole plasma formation dynamics in ZnO

2007

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We employ optical pump-THz probe measurements to study the formation of excitons and electron-hole plasmas following photogeneration of a hot electron-hole gas in the direct gap semiconductor zinc oxide. Below the Mott density, we directly observe the evolution of the hot electron-hole plasma into an insulating exciton gas in the 10 to 100 ps following photoexcitation. The temperature dependence of this process reveals that the rate determining step for exciton formation involves acoustic phonon emission. Above the Mott density, the density of the hot electron-hole plasma initially decreases very rapidly ͑ϳ1.5 ps͒ through Auger annihilation until a stable plasma is formed close to the Mott density. In contrast to exciton formation, Auger annihilation is found to be independent of lattice temperature, occurring while the plasma is still hot.

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“…Interference between the two beams created a spatially periodic intensity and absorption pattern with interference fringe period L ¼ e =2 sinð e =2Þ. Above-band-gap photon absorption in the silicon membrane led to excitation of hot carriers, which promptly transferred energy to the lattice and relaxed to the bottom of the conduction band [25]. Energy was deposited with a sinusoidal intensity profile resulting in a transient thermal ''grating'' with period L, i.e., with carrier population and induced temperature rise modulated as (1 þ cosqx) where q ¼ 2 =L is the grating ''wave-vector'' magnitude; excited carriers and heat subsequently diffused from grating peaks to nulls.…”

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confidence: 99%