共查询到20条相似文献,搜索用时 15 毫秒
1.
J. Hoffman W. Mróz A. Prokopiuk Z. Szymanski 《Applied Physics A: Materials Science & Processing》2008,92(4):921-926
The plasma plume induced during ArF laser ablation of a graphite target is studied. Velocities of the plasma expansion front
are determined by the optical time of flight method. Mass center velocities of the emitting atoms and ions are constant and
amount to 1.7×104 and 3.8×104 m s−1, respectively. Higher velocities of ions result probably from their acceleration in electrostatic field created by electron
emission prior to ion emission. The emission spectroscopy of the plasma plume is used to determine the electron densities
and temperatures at various distances from the target. The electron density is determined from the Stark broadening of the
Ca II and Ca I lines. It reaches a maximum of ∼9.5×1023 m−3 30 ns from the beginning of the laser pulse at the distance of 1.2 mm from the target and next decreases to ∼1.2×1022 m−3 at the distance of 7.6 mm from the target. The electron temperature is determined from the ratio of intensities of ionic
and atomic lines. Close to the target the electron temperature of ∼30 kK is found but it decreases quickly to 11.5 kK 4 mm
from the target. 相似文献
2.
E. Sterling C. Pagano J. G. Lunney 《Applied Physics A: Materials Science & Processing》2008,92(4):1031-1035
For some applications of laser produced plasma it may be advantageous to implement some degree of control on the ion flux
and velocity distribution in the plasma expansion. We have shown how a fast, high current discharge in a laser produced plasma
leads to a dramatic increase in the plasma ionization and expansion velocity. These observations are consistent with a magnetohydrodynamic
discharge model whereby the self-induced magnetic field causes radial compression of an open-ended plasma column. 相似文献
3.
R. Hannachi S. Boussaïdi P. Teulet G. Taieb Y. Cressault A. Gleizes Zohra Ben Lakhdar 《Applied Physics A: Materials Science & Processing》2008,92(4):933-937
A spectroscopic study of the plasma plume created by a laser beam on the surface of NaCl aqueous solution is presented. Optical
emission spectra are recorded and temporally analyzed; electron number density is determined from the Stark broadening of
the NI nitrogen line, and temperature is obtained from relative intensity of OI oxygen lines. The intensity of an atomic line
from sodium was used to quantitate its molar percentage in the Oceanic and Mediterranean sea, and calibration curves have
been constructed for concentrations ranging up to 1.5%. 相似文献
4.
A. V. Rode D. Freeman K. G. H. Baldwin A. Wain O. Uteza Ph. Delaporte 《Applied Physics A: Materials Science & Processing》2008,93(1):135-139
Aligned arrays of N2-encapsulated multilevel branched carbon nanotubes were synthesized using a simple one step CVD method by pyrolysis of ferrocene
and acetonitrile. Electron energy loss spectroscopy (EELS) and elemental mapping studies reveal that gaseous nitrogen was
encapsulated in the carbon nanotubes. Batch-type pyrolysis of catalysts induced flow fluctuation of the reaction gases, resulting
in the growth of branched junctions. Molecular nitrogen extruded rapidly along conical catalyst particles inducing N2 encapsulation inside the branched nanotubes.
PACS 07.78.+s; 61.46.+w; 81.07.De; 81.15.Gh 相似文献
5.
D. Nakamura K. Tamaru T. Akiyama A. Takahashi T. Okada 《Applied Physics A: Materials Science & Processing》2008,92(4):767-772
The dynamics of debris from the laser-produced tin (Sn) plasma was investigated for an extreme ultraviolet light source in
order to establish the guideline for the optimum design of a mitigation system, such as a mass-limited target. The dissemination
of the Sn atoms from the different shapes of a wire and a mass-limited droplet target were investigated using the laser-induced
fluorescence (LIF) imaging method. The Sn droplet targets with a diameter in the range of 5 to 17 μm were prepared by a new
droplet generating technique using a pulsed laser. There was a large difference in the angular distribution of Sn atoms in
the plane parallel and perpendicular to the wire axis, indicating the curvature of the target surface governed the angular
distribution of the ablated species. The spatial distributions of Sn atoms from the droplet targets were similar to those
from the curved surface of the wire targets. The ablation dynamics of the droplet observed by a high-speed imaging camera
is also discussed. 相似文献
6.
B. Tan A. Dalili K. Venkatakrishnan 《Applied Physics A: Materials Science & Processing》2009,95(2):537-545
Thin film laser micromachining has been utilized for repairing semiconductor masks, creating solar cells and fabricating MEMS
devices. A unique high repetition rate femtosecond fiber laser system capable of variable repetition rates from 200 KHz to
25 MHz along with helium gas assist was used to study the effect of pulse repetition rate and pulse energy on femtosecond
laser machining of gold-coated silicon wafer. It was seen that high repetition rates lead to smaller craters with uniform
line width. Craters created at 13 MHz pulse repetition rate with 2.042 J/cm2 beam energy fluence measured 110 nm in width and had a heat affected zone of 0.79 μm. It was found that pulse repetition
rate only played a significant role in the size of the heat affected zone in the lower pulse energy ranges. In the future,
a 1 W laser system will be acquired to find the optimal repetition rate that would create the minimal feature size with the
least heat affected zone. Using this kind of setup along with techniques such as radial polarization and a different gas assist
may enable us to create sub 100 nm feature size with good quality. 相似文献
7.
Cd1−x
Mg
x
Te is an attractive II–VI semiconductor alloy candidate for obtaining energy gaps wider than 1.5 eV of CdTe needed for the
top junction absorber layer in a polycrystalline thin-film tandem solar cell. We have shown that these alloy films can easily
be prepared by sputtering, however, the sputtering rate is substantially lower than for CdTe and the attainable cell performance
has been poor, both before and after activation treatments with chlorine-containing vapors. In this work we have applied optical
emission spectroscopy (OES) using selected peaks of ArII, CdII, MgI, TeII and correlated the results with crystallographic
and morphological characteristics of the deposited films. Results were obtained as a function of rf sputter power and sputter
gas pressure. 相似文献
8.
A. Lorusso J. Krása L. Láska V. Nassisi L. Velardi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):473-476
In the last years the ion component of a laser-produced plasma has been considered and studied as an object to provide high-density
ion sources, which can be applied in many fields such as laser-induced implantation. In this work a KrF laser beam of 108 W/cm2 irradiance was focused onto single-crystalline Fe and single-crystalline Fe with 2% of Si targets and the characteristics
of both free expanding laser-produced plasmas were compared. The time-of-flight (TOF) method was applied to determine the
ion charge yield at various laser fluences and the ion angular spread. The analyses of TOF spectra showed a synergetic effect
of the silicon admixture in target material on the Fe ions production. Besides, this admixture was also responsible of the
increasing of the plasma temperature which corresponds in turn to the increasing of the average kinetic energy of the particles
as well as of the more collimated ion distribution. 相似文献
9.
The generation of relativistic electromagnetic solitons in plasma with spatiotemporal density modulation is investigated.
When two counter-propagating laser pulses overlap in underdense plasma, the interaction between the pulses and plasma modulates
the electron and ion densities resulting in localized, stable, long-living relativistic electromagnetic solitons. They are
caused by the Stimulated Raman Scattering instability. The dependence of the formation of relativistic electromagnetic solitons
on the ion motion, plasma parameters, and laser parameters is studied by particle-in-cell simulations as well. 相似文献
10.
Rok Petkovšek Aleš Babnik Janez Diaci Janez Možina 《Applied Physics A: Materials Science & Processing》2008,93(1):141-145
We present a new method for monitoring of the laser micro-drilling process. The method is based on detection of acoustic waves
in air above the processed sample using a laser beam deflection probe (LBDP). We present an augmentation of the experimental
set-up by means of a digital micrographic system which enables the acquisition of images of the plasma plume and of the hole
cross-section during a drilling sequence. Comparing the acquired images with the detected LBDP signals, we examine the drilling
process from a new perspective. 相似文献
11.
R. Yasukuni T. Asahi T. Sugiyama H. Masuhara M. Sliwa J. Hofkens F. C. De Schryver M. Van der Auweraer A. Herrmann K. Müllen 《Applied Physics A: Materials Science & Processing》2008,93(1):5-9
Highly fluorescent organic nanoparticles with size of about 300 nm were prepared by nanosecond laser ablation of micrometer-sized
powder of dendronized perylenediimide dispersed in water. The nanoparticle colloidal solution provided a fluorescence quantum
yield of 0.58. The absorption and emission spectral studies demonstrated that the bulky dendron groups at the side bays of
perylenediimide chromophore efficiently suppress the interchromophoric interactions in the nanoparticles. Fluorescence measurement
on several single nanoparticles underlines that the prepared nanoparticles are bright and photo-stable enough to be a useful
probe for single particle fluorescence investigation. 相似文献
12.
Chie Hosokawa Suguru N. Kudoh Ai Kiyohara Yoichiroh Hosokawa Kazunori Okano Hiroshi Masuhara Takahisa Taguchi 《Applied Physics A: Materials Science & Processing》2008,93(1):57-63
An all-wet femtosecond laser microprocessing technique was utilized for patterning and cutting functional network of living
neuronal cells on a multi-electrode dish (MED). The neuronal cells cultured on a source substrate were transferred onto an
electrode in a MED probe in solution by utilizing a femtosecond laser-induced impulsive force and a pattern of neuronal cells
were formed on the MED probe. The cellular activity of the detached neurons was supported that neurites could be regenerated
around the electrodes. As another processing method, the neurons stretching between electrodes were selectively cut by the
direct femtosecond laser irradiation and the spontaneous electrical activity of the neuronal network was evaluated. While
the spontaneous action potentials of neurons were synchronized before the cutting, the synchronization disappeared after the
cutting, indicating that the neuronal network is locally disconnected by the laser cutting. The present method is applicable
to artificial reconstruction of living neuronal network. 相似文献
13.
Vanja Margetic Ticijana Ban Ota Samek Franz Leis Kay Niemax Roland Hergenröder 《Czechoslovak Journal of Physics》2004,54(4):423-429
Fluorescence measurements have been used to characterize the velocity of atoms in a femtosecond-laser-produced plasma. Nanogram
amounts of a copper sample were ablated by the focused radiation (λ=775 nm) of an all-solid-state laser. The laser was operated
at a pulse rate of 10 Hz with an energy of 200μJ per pulse. The microplasma expanded into a defined argon atmosphere of pressures between 0.02 and 850 mbar. Atomic fluorescence
was excited in the laser plume by a dye-laser pulse with the wavelength set to the line Cu I 282.4 nm. The narrowed beam of
the dye-laser was directed into the plasma at different heights above the sample surface. The fluorescence radiation was measured
with an échelle-spectrometer, equipped with an intensified-charge-coupled device as the detector. The velocity depends strongly
on the pressure of the ambient atmosphere and the distance from the sample surface. The highest velocity found at an argon
pressure of 0.02 mbar was 1.0×106 cm s−1. 相似文献
14.
Y. Matsuo M. Kurata-Nishimura T. Kobayashi T. Kato Y. Okamura-Oho T. Sano Y. Hayashizaki J. Kawai 《Applied Physics A: Materials Science & Processing》2008,92(4):993-997
We have observed the motion of Sm+ ions as well as Sm atoms produced by femtosecond laser ablation of a solidified samarium solution sample on substrates by
using a planar laser-induced fluorescence method. Kinetic energies of both Sm+ ions and Sm atoms increase as the electrical conductivity of the substrate decreases, which suggests the effect of surface
charging. The kinetic energy of Sm+ ions is larger than that of Sm atoms for a variety of substrates due to the further electrical acceleration by the surface
charge. The knowledge of ion motion will be the key information for the optimization of femtosecond laser simultaneous atomization
and ionization of organic and inorganic samples on substrates. 相似文献
15.
Stefan Haas Gunnar Schöpe Christoph Zahren Helmut Stiebig 《Applied Physics A: Materials Science & Processing》2008,92(4):755-759
A detailed analysis of the monolithical series connection of thin-film silicon modules with ZnO/Ag back contact is presented.
In this study, pulsed lasers with wavelengths of 1064 nm and 532 nm were used. The influence of various laser parameters like
laser power, pulse overlap, etc., on the different patterning steps is discussed. The focus of this study was on the back
contact patterning process. Here (i) the flake formation process during the ablation and (ii) the influence of a NIR-laser
source as an alternative approach to the green laser were investigated in detail. The latter would reduce system costs if
only one NIR-laser source could be used for all patterning steps. 相似文献
16.
Z. Q. Huang M. H. Hong T. B. M. Do Q. Y. Lin 《Applied Physics A: Materials Science & Processing》2008,90(1):159-163
TiB2-based cermets are prepared by combustion synthesis followed by a pressing stage in a granulate medium. Products obtained
by combustion synthesis are characterized by a large remaining porosity (typically 50%). To produce dense cermets, a subsequent
densification step is performed after the combustion process and when the reacted material is still hot. To design the process,
numerical simulations are carried out and compared to experimental results. In addition, physical and electrical properties
of the products related to electrical contact applications are evaluated.
PACS 81.20.Ka; 81.05.Mh; 72.80.Tm 相似文献
17.
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
18.
Spatially resolved measurements of vibrational and rotational temperature determined from the N2(C) nitrogen bands intensities have been performed by means of optical scanner of original construction. It has been found
that radial variations of studied bands are independent of pressure and discharge current under our experimental conditions,
i.e. in the pressure range (100–300) Pa and for discharge current up to 40 mA. Moreover, it has been found that vibrational
as well as rotational temperatures stay almost constant in the radial direction. No radial changes of both temperatures can
be explained by good thermal conductivity of the positive column of DC glow discharge.
This research was supported by grants: Charles University No. GAUK 194/01, Ministry of Education of Czech Republic MSM 11320002,
and Grant Agency of Czech Republic GAČR 202/03/0827. The theme of presented article was included in the EU project No. G1RT-CT-2002-05083
“Plasmatech”. 相似文献
19.
J. J. J. Kaakkunen K. Paivasaari M. Kuittinen T. Jaaskelainen 《Applied Physics A: Materials Science & Processing》2009,94(2):215-220
Recently, the enhancing of bulk metals optical absorption with focused femtosecond pulses was demonstrated. This absorption
enhancement is caused by different nano- and micro-structures which are formed during laser ablation with ultrashort pulses.
In this paper we study the evolution of the surface structures using interferometric ablation and compare it to normal fs-ablation.
Previously we have shown that interferometric femtosecond ablation is an efficient method to fabricate absorbing metal surfaces.
In this study we ablated large areas of hole-array structures with different pulse numbers in polished stainless steel and
copper samples. The evolution of surface morphology and the depth of the holes for these structured surfaces are presented.
In addition, the reflectance of laser generated surface structures are measured at the wavelength range of 200–2300 nm using
a standard spectrophotometer. 相似文献
20.
A. A. Morozov Z. Geretovszky L. Égerházi T. Szörényi 《Applied Physics A: Materials Science & Processing》2008,93(3):691-696
A simple analytical model for inverse pulsed laser deposition is proposed. In the model the motion of the evaporated material
is assumed to emerge as from a point source located above the surface of evaporation at some distance. The obtained thickness
profiles of inverse deposited films agree well with those calculated by the test particle Monte Carlo method. The proposed
approach has been applied for analysis of experimental data on inverse pulsed laser deposition of graphite in nitrogen atmosphere
with nanosecond pulses of laser fluences between 1 and 7 J/cm2. The model describes well the thickness profiles and pressure dependence of film growth rate for inverse deposition. 相似文献