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1.
Hidetoshi Nakano Katsuya Oguri Yasuaki Okano Tadashi Nishikawa 《Applied Physics A: Materials Science & Processing》2010,101(3):523-531
We investigated spatiotemporal evolution of expanding ablation plume of aluminum created by a 100-fs, 1014–1015-W/cm2 laser pulse. For diagnosing dynamic behavior of ablation plume, we employed the spatiotemporally resolved X-ray absorption
spectroscopy (XAS) system that consists of a femtosecond-laser-plasma soft X-ray source and a Kirkpatrick–Baez (K–B) microscope.
We successfully assigned the ejected particles by analyzing structure of absorption spectra near the L
II,III absorption edge of Al, and we clarified the spatial distribution of Al+ ions, Al atoms, and liquid droplets of Al in the plume. We found that the ejected particles strongly depend the irradiated
laser intensity. The spatial distribution of atomic density and the expansion velocity of each type of particle were estimated
from the spatiotemporal evolution of ablation particles. We also investigated a temperature of the aluminum fine particles
in liquid phase during the plume expansion by analyzing the slope of the L
II,III absorption edge in case of 1014-W/cm2 laser irradiation where the nanoparticles are most efficiently produced. The result suggests that the ejected particles travel
in a vacuum as a liquid phase with a temperature of about 2500 to 4200 K in the early stage of plume expansion. 相似文献
2.
B. Hopp G. Kecskeméti T. Smausz T. Ajtai A. Filep N. Utry A. Kohut Z. Bozóki G. Szabó 《Applied Physics A: Materials Science & Processing》2012,107(2):429-435
Preparation of organic thin layers on various special substrates using the pulsed laser deposition (PLD) technique is an important
task from the point of view of bioengineering and biosensor technologies. Earlier studies demonstrated that particle ejection
starts during the ablating laser pulse resulting in significant shielding effects which can influence the real fluence on
the target surface and consequently the efficiency of layer preparation. In this study, we introduce a photoacoustic absorption
measurement technique for in-situ characterization of ablated particles during PLD experiments. A KrF excimer laser beam (λ=248 nm, FWHM=18 ns) was focused onto pepsin targets in a PLD chamber; the applied laser fluences were 440 and 660 mJ/cm2. We determined the wavelength dependence of optical absorption and mass specific absorption coefficient of laser ablation
generated pepsin aerosols in the UV–VIS–NIR range. On the basis of our measurements, we calculated the absorbance at the ablating
laser wavelength, too. We demonstrated that when the laser ablation generated pepsin aerosols spread through the whole PLD
chamber the effect of absorptivity is negligible for the subsequent pulses. However, the interaction of the laser pulse and
the just formed particle cloud generated by the same pulse is more significant. 相似文献
3.
M. H. Mahdieh H. Hosseini?Shokoh 《Applied Physics A: Materials Science & Processing》2012,106(4):995-1004
In this paper we present evidence for a phase explosion during the laser-induced ablation process by studying the optical
reflectivity of the ablated plume. The ablation was produced by irradiating thin film aluminum coated on a quartz substrate
with a single pulse laser beam in ambient air. The laser pulse was provided by the second harmonic of a Q-switched Nd:YAG
laser with ∼10 ns pulse duration. The transmission of a low power He–Ne laser beam through the hot ablated material plume
and its reflection (from the front surface, and rear surface of aluminum film) were also monitored during the duration of
the ablation event. The results show that the front surface reflectivity is enhanced at an early time of ablation which is
described as strong evidence for the creation of a phase explosion in this process. 相似文献
4.
Molecular imaging by Mid-IR laser ablation mass spectrometry 总被引:1,自引:0,他引:1
Akos Vertes Peter Nemes Bindesh Shrestha Alexis A. Barton Zhaoyang Chen Yue Li 《Applied Physics A: Materials Science & Processing》2008,93(4):885-891
Mid-IR laser ablation at atmospheric pressure (AP) produces a mixture of ions, neutrals, clusters, and particles with a size
distribution extending into the nanoparticle range. Using external electric fields the ions can be extracted and sampled by
a mass spectrometer. In AP infrared (IR) matrix-assisted laser desorption ionization (MALDI) experiments, the plume was shown
to contain an appreciable proportion of ionic components that reflected the composition of the ablated target and enabled
mass spectrometric analysis. The detected ion intensities rapidly declined with increasing distance of sampling from the ablated
surface to ∼4 mm. This was rationalized in terms of ion recombination and the stopping of the plume expansion by the background
gas. In laser ablation electrospray ionization (LAESI) experiments, the ablation plume was intercepted by an electrospray.
The neutral particles in the plume were ionized by the charged droplets in the spray and enabled the detection of large molecules
(up to 66 kDa). Maximum ion production in LAESI was observed at large (∼15 mm) spray axis to ablated surface distance indicating
a radically different ion formation mechanism compared to AP IR-MALDI. The feasibility of molecular imaging by both AP IR-MALDI
and LAESI was demonstrated on targets with mock patterns.
Presented at the 9-th International Conference on Laser Ablation, 2007 Tenerife, Canary Islands, Spain 相似文献
5.
Ablation of organic polymers is described on the basis of photothermal bond breaking within the bulk material. Here, we assume
a first-order chemical reaction, which can be described by an Arrhenius law. Ablation starts when the density of broken bonds
at the surface reaches a certain critical value.
In order to understand the ablation behavior near the threshold fluence, φth, non-stationary regimes must be considered. The present treatment reveals several qualitative differences with respect to models that treat
ablation as a surface process: (i) Ablation starts sharply with a front velocity that has its maximum value just after the onset. (ii) The transition
to the quasi-stationary ablation regime is faster. (iii) Near threshold, the ablated depth h has a square-root dependence
on laser fluence, i.e., h∝(φ-φth)1/2. The ablation velocity is very high even near φth. (iv) With φ≈φth ablation starts well after the laser pulse. (v) The depletion of species is responsible for the Arrhenius tail observed with
fluences φ≤φth. (vi) Residual modification of material has maximum near the threshold. (vii) Stationary regimes of ablation demonstrate change of effective activation energy with laser intensity.
The model calculations are applied to Polyimide (KaptonTM H). Here, differences in single-pulse ablated depth determined from mass loss and profilometry should be about 10 nm.
Received: 16 February 1999 / Accepted: 18 February 1999 / Published online: 28 April 1999 相似文献
6.
V. I. Nasonov 《Journal of Applied Spectroscopy》2006,73(2):234-244
Radiation scattering by particles of condensed phase in an ablation plasma plume has been experimentally studied during quasicontinuous
laser irradiation (λ = 1.06 μm, q = 0.1–9 MW/cm2, τ ∼ 1.5 msec) of duraluminum D16T, aluminum A99, and bismuth. The particle size distribution and the nature of their dispersal
during irradiation was studied in scattered light (λ = 0.69 μm) from individual particles that could be visually observed
on photographs. It was found that under the pressure developed in the plume, large particles ejected from the irradiated zone
can move backward and return to the target (D16T). The plume (Bi) becomes brighter due to ablation of particles in the path
of the laser beam. The directional scattering coefficients for scattering from the local zone on the axis of the plume, measured
during the laser pulse, were used to study the relationship between the dynamics of entry of condensed phase into the plume,
shielding of the target by the particles, and brightening of the plume under the action of the incident laser radiation.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 210–219, March–April, 2006. 相似文献
7.
S. Canulescu T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2008,93(3):771-778
The mass distributions of the species generated by laser ablation from a La0.6Ca0.4MnO3 target using laser irradiation wavelengths of 193 nm, 266 nm and 308 nm have been investigated with and without a synchronized
gas pulse of N2O. The kinetic energies of the species are measured using an electrostatic deflection energy analyzer, while the mass distributions
of the species were analyzed with a quadrupole mass filter.
In vacuum (pressure 10−7 mbar), the ablation plume consists of metal atoms and ions such as La, Ca, Mn, O, LaO, as well as multiatomic species, e.g.
LaMnO+. The LaO+ diatomic species are by far the most intense diatomic species in the plume, while CaO and MnO are only detected in small
amounts.
The interaction of a reactive N2O gas pulse with the ablation plume leads to an increase in plume reactivity, which is desired when thin manganite films are
grown, in order to incorporate the necessary amount of oxygen into the film. The N2O gas pulse appears to have a significant influence on the oxidation of the Mn species in the plume, and on the creation of
negative ions, such as LaO−,O− and O2−. 相似文献
8.
Weisbuch F. Tokarev V.N. Lazare S. Débarre D. 《Applied Physics A: Materials Science & Processing》2003,76(4):613-620
A microscopic flow of a transient liquid film produced by KrF laser ablation is evidenced on targets of PET and PEN. Experiments
were done by using single pulses of the excimer laser beam micropatterned with the aid of submicron projection optics and
grating masks. The samples of various crystalline states, ablated with a grating-forming beam (period Λ=3.7 μm), were precisely
measured by atomic force microscopy, in order to evidence any deviation from the ablation behavior predicted by the current
theory (combination of ablation curve and beam profile). This was confirmed by comparing various behaviors dependent on the
polymer nature (PC, PET and PEN). PC is a normally ablating polymer in the sense that the ablated profile can be predicted
with previous theory neglecting liquid-flow effects. This case is called ‘dry’ ablation and PC is used as a reference material.
But, for some particular samples like crystalline PET, it is revealed that during ablation a film of transient liquid, composed
of various components, which are discussed, can flow under the transient action of the gradient of the pressure of the ablation
plume and resolidify at the border of the spot after the end of the pulse. This mechanism is further supported by a hydrodynamics
theoretical model in which a laser-induced viscosity drop and the gradient of the plume pressure play an important role. The
volume of displaced liquid increases with fluence (0.5 to 2 J/cm2) and satisfactory quantitative agreement is obtained with the present model. The same experiment done on the same PET polymer
but prepared in the amorphous state does not show microflow, and such an amorphous sample behaves like the reference PC (‘dry’
ablation). The reasons for this surprising result are discussed.
Received: 31 October 2002 / Accepted: 4 November 2002 / Published online: 22 January 2003
RID="*"
ID="*"Present address: ST Microelectronics, Crolles, France
RID="**"
ID="**"Corresponding author. Fax: +33-556/84-6645, E-mail: s.lazare@lpcm.u-bordeaux1.fr 相似文献
9.
Xing Fan 《Applied Surface Science》2009,255(12):6297-6302
Particles generated by 2.94 μm pulsed IR laser ablation of liquid 3-nitrobenzyl alcohol were irradiated with a 351 nm UV laser 3.5 mm above and parallel to the sample target. The size and concentration of the ablated particles were measured with a light scattering particle sizer. The application of the UV laser resulted in a reduction in the average particle size by one-half and an increase in the total particle concentration by a factor of nine. The optimum delay between the IR and UV lasers was between 16 and 26 μs and was dependent on the fluence of the IR laser: higher fluence led to a more rapid appearance of particulate. The ejection velocity of the particle plume, as determined by the delay time corresponding to the maximum two-laser particle concentration signal, was 130 m/s at 1600 J/m2 IR laser fluence and increased to 220 m/s at 2700 J/m2. The emission of particles extended for several ms. The observations are consistent with a rapid phase change and emission of particulate, followed by an extended emission of particles ablated from the target surface. 相似文献
10.
P. M. Ossi F. Neri N. Santo S. Trusso 《Applied Physics A: Materials Science & Processing》2011,104(3):829-837
Silver and gold thin films were deposited by pulsed laser ablation in a controlled Ar atmosphere at pressures between 10 and
100 Pa. Different morphologies, ranging from isolated nanoparticle arrays up to nanostructured thin films were observed. Fast
imaging of the plasma allowed deducing the expansion dynamics of the ablated plume. Plasma velocity and volume were used together
with the measured average ablated mass per pulse as input parameters in a model to estimate the average size of nanoparticles
grown in the plume. The nanoparticle size is expected to decrease from 4 nm down to 1 nm with decreasing Ar pressure between
100 and 10 Pa: this was confirmed by transmission electron micrographs which indicate a reduced dispersion of particle size
over narrow size ranges. The production of substrates for surface enhanced Raman scattering whose performances critically
depend on nanoparticle size, shape, and structure is discussed. 相似文献
11.
We measured the momentum coupling coefficient Cm and laser-generated ion drift velocity and temperature in the femtosecond (fs) region, over a laser intensity range from ablation threshold to about one hundred times threshold. Targets were several pure metals and three organic compounds. The organic compounds were exothermic polymers specifically developed for the micro-laser plasma thruster, and two of these used “tuned absorbers” rather than carbon particles for laser absorption. The metals ranged from Li to W in atomic weight. We measured time of flight (TOF) profiles for ions. Specific impulse reached record values for this type of measurement and ablation efficiency was near 100%. These measurements extend the laser pulsewidth three orders of magnitude downward in pulsewidth relative to previous reports. Over this range, we found Cm to be essentially constant. Ion velocity ranged from 60 to 180 km/s. 相似文献
12.
M. Miyabe M. Oba H. Iimura K. Akaoka Y. Maruyama I. Wakaida 《Applied Physics A: Materials Science & Processing》2010,101(1):65-70
A cerium oxide sample was ablated by 2nd harmonic radiation of Nd:YAG laser at a power density of 0.1 GW/cm2. Time evolution of the ablation plume was investigated by laser absorption time-of-flight (TOF) measurement. It was found
that the ablated ionic plume in vacuum consisted of two components having different velocities whereas the ablated neutral
atoms had mainly a single component. The flow velocity perpendicular to the sample surface in vacuum was determined to be
3.5 km/s for neutral atoms, and 4.7 km/s and 9.3 km/s for singly charged ions. From the detailed plume evolution in ambient
atmosphere with several pressures we obtained some experimental conditions suitable for isotope analysis of atomic cerium. 相似文献
13.
S. C. Singh 《Journal of nanoparticle research》2011,13(9):4143-4152
Zinc oxide/hydroxide nanocomposite materials are synthesized by pulsed laser ablation of zinc in double distilled water. Effect
of simultaneous flow of oxygen in the closed vicinity of laser ablated plasma plume on the size, morphology, crystallinity,
and composition of synthesized oxide/hydroxide nanocomposite structures is investigated. As synthesized nanocomposite materials
are characterized using UV–visible absorption, Scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), Differential
thermal analysis (DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and photoluminescence spectroscopic methods.
It is observed that injection of oxygen induces a new mechanism in the particle synthesis, which causes decrease in particle
size, distribution as well as Zn(OH)2/ZnO ratio and increase of order of crystallinity of product. There are some novel findings in the direction of development
of pulsed laser ablation in aqueous media (PLAAM) for the synthesis of nanostructured materials. 相似文献
14.
Kedar Pathak 《Applied Surface Science》2007,253(15):6359-6365
The process of laser ablation of carbon in presence of background gas is simulated numerically. The plume dynamics in laser ablation is important to study for many reasons including temperature of plume particles and shielding of target by previously ablated plumes. Shielding leads directly to the change in energy deposition of incident laser pulse at the target surface and in turn influences the ablation dynamics and amount of material removed. Carbon ablation is studied for single and multiple laser hits typical for synthesis of nanotubes. Two models of correction of ablated velocity and pressure resulting from shielding effect are proposed and investigated. Numerical modeling of this plume dynamics and its integral effect of shielding is challenging due to inherent high nonlinearity of the problem. Some of available numerical techniques handles nonlinearity but are dissipative, e.g. Godunov type schemes. Other techniques are less dissipative but fail to account for strong nonlinearity typical for initial stages of ablation, e.g. the ENO-Roe. To effectively model this highly nonlinear plume dynamics a combination of two of above mentioned schemes is developed so as the numerical evaluation of fluxes is close to their physical values and the scheme has minimum dissipation. The non-monotonic behavior of ablated mass as a function of time duration between two laser pulses is studied. 相似文献
15.
16.
3 ) at wavelengths ranging from the ultraviolet to the mid-infrared, including a Nd:YAG laser operated at the fundamental, second
and third harmonics, and a tunable infrared free-electron laser (wavelength range 2.5–8 μm). The threshold for ablation and
the topography of the irradiated spot were characterized by scanning electron microscopy. A clear indication of two distinct
excitation mechanisms was observed, namely, cracks and fractures followed by exfoliation at ultraviolet to near-infrared wavelengths,
in contrast to evaporative holes and scattered droplets in the mid-infrared. Plume emission/absorption spectroscopy, plume
transmission and photoacoustic beam deflection were used to characterize the ablation plasma. The composition of atoms, molecules,
or particles in the ablation plumes also has a distinctive variation as a function of the wavelength. The excitation mechanisms
leading to ablation appear to be defect activation at ultraviolet to near-infrared wavelengths, molecular impurity absorption
and resonant vibrational absorption of the calcite at mid-infrared.
Received: 5 December 1996/Accepted: 6 January 1997 相似文献
17.
S. L. Johnson D. M. Bubb R. F. Haglund 《Applied Physics A: Materials Science & Processing》2009,96(3):627-635
We investigate the phenomenon of resonant-infrared laser ablation of polymers using polystyrene as a model material. Ablation
is carried out using various mid-IR laser wavelengths that are resonant with vibrational modes of a polystyrene target. Time-resolved
plume imaging coupled with etch-depth measurements and thermal calculations indicate that ablation begins after a superheated
surface layer reaches a temperature of ∼1000°C and undergoes spinodal decomposition. The majority of the ablated material
is then expelled by way of recoil-induced ejection as the pressure of the expanding vapor plume compresses a laser-melted
area. 相似文献
18.
The effect of laser ablation on copper foil irradiated by a short 30 ns laser pulse was investigated by X-ray photoelectron spectroscopy. The laser fluence was varied from 8 to 16.5 J/cm2 and the velocity of the laser beam from 10 to 100 mm/s. This range of laser fluence is characterized by a different intensity of laser ablation. The experiments were done in two kinds of ambient atmosphere: air and argon jet gas.The chemical state and composition of the irradiated copper surface were determined using the modified Auger parameter (α′) and O/Cu intensity ratio. The ablation atmosphere was found to influence the size and chemical state of the copper particles deposited from the vapor plume. During irradiation in air atmosphere the copper nanoparticles react with oxygen and water vapor from the air and are deposited in the form of a CuO and Cu(OH)2 thin film. In argon atmosphere the processed copper surface is oxidized after exposure to air. 相似文献
19.
N. G. Semaltianos W. Perrie P. French M. Sharp G. Dearden S. Logothetidis K. G. Watkins 《Applied Physics A: Materials Science & Processing》2009,94(4):999-1009
Femtosecond laser (180 fs, 775 nm, 1 kHz) ablation characteristics of the nickel-based superalloy C263 are investigated. The
single pulse ablation threshold is measured to be 0.26±0.03 J/cm2 and the incubation parameter ξ=0.72±0.03 by also measuring the dependence of ablation threshold on the number of laser pulses.
The ablation rate exhibits two logarithmic dependencies on fluence corresponding to ablation determined by the optical penetration
depth at fluences below ∼5 J/cm2 (for single pulse) and by the electron thermal diffusion length above that fluence. The central surface morphology of ablated
craters (dimples) with laser fluence and number of laser pulses shows the development of several kinds of periodic structures
(ripples) with different periodicities as well as the formation of resolidified material and holes at the centre of the ablated
crater at high fluences. The debris produced during ablation consists of crystalline C263 oxidized nanoparticles with diameters
of ∼2–20 nm (for F=9.6 J/cm2). The mechanisms involved in femtosecond laser microprocessing of the superalloy C263 as well as in the synthesis of C263
nanoparticles are elucidated and discussed in terms of the properties of the material. 相似文献
20.
The study aims at modeling of plume shielding aspects of laser ablation processes with multiple laser pulses applied to multiple targets. The main obstacle with the efficient use of multiple laser pulse technologies is an attenuation of the laser irradiation by previously ablated plumes. Dynamics of plumes is described by the axisymmetric Euler equations describing a vapor-droplet ablated mixture rolling-up in the surrounding ideal gas. For multiple laser pulses, the role of absorption of laser beam by previously ablated plumes is evaluated varying a model parameter that defines the fraction of laser energy absorbed by the ablated mixture. Absorption of laser beam by plume may cause its secondary explosion that cleans the target surface and, subsequently, increases the mass ablated by the consequent pulse. Dynamics of plumes ablated from two targets with possible time delay between two laser hits is investigated as a representative case of multiple targets. Shielding of the surface between targets appears to be significant if the second pulse occurs before the first shock wave passes the second target. 相似文献