Short-pulse ablation rates and the two-temperature model

Christensen, B.H.; Vestentoft, Kasper; Balling, P.

doi:10.1016/j.apsusc.2007.01.045

Cited by 135 publications

(84 citation statements)

References 24 publications

(28 reference statements)

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“…The electron-phonon coupling strength is difficult to determine. Experimentally, this quantity may be obtained by evaluating ablation rates 47 , measuring the thermoreflectance 48 or optical reflection 49 . However, these experiments are often performed at low laser intensities, which are not comparable to the SHI irradiation scenario.…”

Section: Discussionmentioning

confidence: 99%

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

et al. 2014

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The controlled creation of defects in silicon carbide represents a major challenge. A wellknown and efficient tool for defect creation in dielectric materials is the irradiation with swift (E kin Z500 keV/amu) heavy ions, which deposit a significant amount of their kinetic energy into the electronic system. However, in the case of silicon carbide, a significant defect creation by individual ions could hitherto not be achieved. Here we present experimental evidence that silicon carbide surfaces can be modified by individual swift heavy ions with an energy well below the proposed threshold if the irradiation takes place under oblique angles. Depending on the angle of incidence, these grooves can span several hundreds of nanometres. We show that our experimental data are fully compatible with the assumption that each ion induces the sublimation of silicon atoms along its trajectory, resulting in narrow graphitic grooves in the silicon carbide matrix.

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Section: Discussionmentioning

confidence: 99%

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

et al. 2014

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“…The two temperature model has been widely employed for metal ablation with ultrashort pulse lasers: Cu, 7 Au, 8 ' 9 Al 10 -11 and Ag. 11 Although the present work is focused on nanosecond lasers, the two temperature model implemented is intended to allow further applications to ultrashort laser pulse interaction with materials, especially when it is taken into account that these lasers have started to use at laboratory level in researches for PV. 5 In order to validate simulation results, experimental tests were also carried out at the laboratory, for which different laser processing conditions in accordance with simulated parameters were analysed.…”

Section: Introductionmentioning

confidence: 99%

Laser ablation modelling of aluminium, silver and crystalline silicon for applications in photovoltaic technologies

Colina

Molpeceres

Morales

et al. 2011

Surface Engineering

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Laser material processing is being extensively used in photovoltaic applications for both the fabrication of thin film modules and the enhancement of the crystalline silicon solar cells. The two temperature model for thermal diffusion was numerically solved in this paper. Laser pulses of 1064, 532 or 248 nm with duration of 35, 26 or 10 ns were considered as the thermal source leading to the material ablation. Considering high irradiance levels (10 8 -10 9 W cm -2 ), a total absorption of the energy during the ablation process was assumed in the model. The materials analysed in the simulation were aluminium (Al) and silver (Ag), which are commonly used as metallic electrodes in photovoltaic devices. Moreover, thermal diffusion was also simulated for crystalline silicon (c-Si). A similar trend of temperature as a function of depth and time was found for both metals and c-Si regardless of the employed wavelength. For each material, the ablation depth dependence on laser pulse parameters was determined by means of an ablation criterion. Thus, after the laser pulse, the maximum depth for which the total energy stored in the material is equal to the vaporisation enthalpy was considered as the ablation depth. For all cases, the ablation depth increased with the laser pulse fluence and did not exhibit a clear correlation with the radiation wavelength. Finally, the experimental validation of the simulation results was carried out and the ability of the model with the initial hypothesis of total energy absorption to closely fit experimental results was confirmed.

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“…Temperature-dependent electron-phonon coupling is logical because g depends on the driving force for energy exchange between electron and vibrational populations, and has been observed in hot electron photoemission experiments (23)(24)(25)(26), but has not been considered in experiments that measure hot electron cooling rates in metal NPs, because these experiments used low laser intensities that were assumed to create sufficiently small electronic temperatures to remain in a temperature-independent regime of the electron-phonon coupling. We find, however, that inclusion of a temperature dependence for g significantly improves the fits of all of the kinetic data, even those collected at low excitation power.…”

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confidence: 99%

Identification of parameters through which surface chemistry determines the lifetimes of hot electrons in small Au nanoparticles

Aruda

Tagliazucchi

Sweeney

et al. 2013

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

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This paper describes measurements of the dynamics of hot electron cooling in photoexcited gold nanoparticles (Au NPs) with diameters of ∼3.5 nm, and passivated with either a hexadecylamine or hexadecanethiolate adlayer, using ultrafast transient absorption spectroscopy. Fits of these dynamics with temperature-dependent Mie theory reveal that both the electronic heat capacity and the electron-phonon coupling constant are larger for the thiolated NPs than for the aminated NPs, by 40% and 30%, respectively. Density functional theory calculations on ligand-functionalized Au slabs show that the increase in these quantities is due to an increased electronic density of states near the Fermi level upon ligand exchange from amines to thiolates. The lifetime of hot electrons, which have thermalized from the initial plasmon excitation, increases with increasing electronic heat capacity, but decreases with increasing electronphonon coupling, so the effects of changing surface chemistry on these two quantities partially cancel to yield a hot electron lifetime of thiolated NPs that is only 20% longer than that of aminated NPs. This analysis also reveals that incorporation of a temperaturedependent electron-phonon coupling constant is necessary to adequately fit the dynamics of electron cooling. two-temperature model | dissipation T his paper describes an observed dependence of two physical properties-the electronic heat capacity and the electronphonon coupling magnitude-of small (diameter of ∼3.5 nm), completely absorptive plasmonic gold nanoparticles (Au NPs) on the surface chemistry of the NPs. The electronic heat capacity, quantified by the coefficient γ, is the amount of energy required to change the temperature of a population of electrons in the NP. The magnitude of the electron-phonon coupling, quantified by the coefficient g, is a measure of the rate of exchange of energy between the electrons and the lattice. Upon photoexcitation of the Au NPs at the absorption maximum of their plasmon resonance, the plasmonic electron oscillation in the NPs rapidly decoheres to form a thermally equilibrated population of hot electrons (1-8). Within the commonly used "two-temperature model (2TM)," the rate of subsequent cooling of these electrons is dictated by the initial electronic temperature of the particle and the efficiency of dissipation of electronic energy into available vibrational modes. These properties, in turn, depend on the electronic heat capacity of the system and the magnitude of electron-phonon coupling. Our observed dependence of the coefficients γ and g on the chemical structure of the organic adlayer therefore implies that electronic states that participate in the electron cooling process are not only those of the gold lattice, but also orbitals at the metal-organic interface-that is, the surface chemistry of the NPs influences the rate of hot electron cooling.Interest in using metal and semiconductor NPs as optical and/or electronic components within energy conversion systems (9, 10) has inspired studies of ene...

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Short-pulse ablation rates and the two-temperature model

Cited by 135 publications

References 24 publications

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

Laser ablation modelling of aluminium, silver and crystalline silicon for applications in photovoltaic technologies

Identification of parameters through which surface chemistry determines the lifetimes of hot electrons in small Au nanoparticles

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