Ultrafast electronic disordering during femtosecond laser melting of GaAs

Saeta, Peter N.; Wang, J.-K.; Siegal, Y.; Bloembergen, N.; Mazur, Eric

doi:10.1103/physrevlett.67.1023

Cited by 233 publications

(94 citation statements)

References 16 publications

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“…Most of them are based on time-resolved second harmonic generation (SHG), which vanishes when the crystal loses its symmetry. It has been reported, that this process occurs on time scales which are shorter than the typical energy transfer times from the electronic system to the lattice 103,104,105]. Theoretically it has been predicted that a non-thermal phase transition may occur when more than 9% of all valence electrons are excited into antibonding conduction band states 106, 1 0 7 ].…”

Section: Impulsive Mode Softening Of Phononsmentioning

confidence: 99%

Coherent phonons in condensed media

Dekorsy¹,

Cho²,

Kurz³

2000

Topics in Applied Physics

139

127

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Abstract. The impulsive excitation and phase-sensitive detection of coherent phonons and phonon-polaritons provide a detailed insight i n to the dynamical properties of matter. The experiments are based on optical pump-probe techniques with femtosecond time resolution. These techniques enable the detection of amplitude and phase of the coherent lattice motion simultaneously. F requencies in the THz range and dephasing times in the picosecond range can be obtained with high accuracy. Especially in semiconductors and semiconductor heterostructures, where a coherent phonon mode and free carriers are excited simultaneously, important information about carrier-phonon interaction far away from equilibrium is obtained. This paper presents an overview of recent a c hievements in this vivid eld of condensed matter physics.

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Section: Impulsive Mode Softening Of Phononsmentioning

confidence: 99%

Coherent phonons in condensed media

Dekorsy¹,

Cho²,

Kurz³

2000

Topics in Applied Physics

139

127

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“…To simulate the temporal changes of the integrated X-ray intensity for the single-crystal film, we consider the following simple, coupled-rate equations: 4] where N m ðtÞ describes the population change of the melted layers after reaching the peak at 15 ps, as illustrated in Fig. 4A.…”

Section: Ps) (Ii) Excitation Energymentioning

confidence: 99%

Time-resolved structural dynamics of thin metal films heated with femtosecond optical pulses

Chen

Tang

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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We utilize 100 fs optical pulses to induce ultrafast disorder of 35-to 150-nm thick single Au(111) crystals and observe the subsequent structural evolution using 0.6-ps, 8.04-keV X-ray pulses. Monitoring the picosecond time-dependent modulation of the X-ray diffraction intensity, width, and shift, we have measured directly electron/phonon coupling, phonon/lattice interaction, and a histogram of the lattice disorder evolution, such as lattice breath due to a pressure wave propagating at sonic velocity, lattice melting, and recrystallization, including mosaic formation. Results of theoretical simulations agree and support the experimental data of the lattice/liquid phase transition process. These time-resolved X-ray diffraction data provide a detailed description of all the significant processes induced by ultrafast laser pulses impinging on thin metallic single crystals.ultrafast X-ray diffraction | laser-induced phase transition | coherent phonon | annealing | grain growth L attice disorder and phase transition in metal, semiconductor, and alloy are of vital importance in both fundamental science and technology. Irradiation with femtosecond laser pulses induces lattice disorder (1), which could be (i) a purely electronic nonthermal order-disorder process by injecting carriers into bulk semiconductor crystals, such as Si (2, 3) and GaAs (4, 5) within 1 ps; (ii) a purely thermal-disorder thermal process that depends on electron/phonon, phonon/phonon, and phonon/lattice interaction time in metal films, especially in noble metals, such as Au (6, 7); (iii) a combination of thermal-and nonthermal-disorder with the ratio depending on the laser fluence (8). When the laser fluence is sufficient, the phase transition from solid to liquid will occur and the melting process is considered to involve both thermal and nonthermal processes, whereas in gold (9-11) and aluminum films, which is the dominant process is still under debate (12-14). The laser heating and melting of the gold film studies presented in this paper were induced by low excitation levels, therefore the electronic effects on the stability of the lattice are not expected to occur (15), which is in contrast to the high excitation levels used for electronic hardening in gold (10).In this paper, we describe experiments that utilize subpicosecond time-resolved X-ray diffraction (XRD) to measure directly the transient changes in the crystal structure induced by 400-nm, 100-fs laser pulses impinging upon the surface of 35-, 70-, and 150-nm-thick Au(111) single-crystal films. The experiments presented here may be assigned to a weak excitation region, at fluence lower than 15 mJ∕cm 2 , where the blast wave and coherent phonons were observed, and a strong excitation region, at fluencies of 37 mJ∕cm 2 and above, where melting occurs. In addition, a pressure blast wave, formed immediately upon excitation, induced lattice contraction (16) that propagated through the bulk of the crystal at sonic velocity, generating stress and the wellknown sonic wave. We will show that, i...

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“…For irradiation with pulses longer than several picoseconds and for near-threshold femtosecond pulses, following nucleation of the liquid phase at the surface, a thin liquid layer grows into the bulk of the material at a velocity limited by the speed of sound, but typically at a rate on the order of angstroms per picoseconds. In contrast, for fluences twice the melting threshold or greater [12][13][14][15] a significantly faster, sub-picosecond change of the linear optical properties at the surface is seen, with reflectivities reaching values equal to that of the conventional liquid phase in a few hundred femtoseconds [15]. In other experiments, a reduction in the second-harmonic-inreflection signal, suggesting a sub-picosecond loss of crystalline order at the very surface, was also seen [12,14].…”

Section: Introductionmentioning

confidence: 89%