共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
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
3.
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
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.
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
6.
P. Haro-González I. R. Martin F. Lahoz S. González-Pérez N. E. Capuj D. Jaque 《Applied Physics A: Materials Science & Processing》2008,93(4):977-981
Localized desvitrifiation in strontium barium niobate glass doped with Er3+ under laser irradiation has been carried out. The samples of this study have been fabricated by the melt quenching method
and doped with 5% mol of Er3+. A 1.5-W cw Ar laser was focused on the sample to obtain desvitrifiation of the glass. Evidence of the changes induced by
the Ar laser has been observed through the analysis of the photoluminescence of the Er3+ ions. The transitions corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 have been studied to analyze structure changes. Microluminescence measurements have been carried out to spatially select
positions inside and outside the irradiated area. We have observed changes in the emission bands corresponding to these transitions.
The emission bands from Er3+ ions in the irradiated zone show a resolved structure while they are broadened outside that area. These changes in the optical
properties of the Er3+ ions indicate that the Ar-laser irradiation has produced a change in the local structure of the material. These results show
that a localized desvitrifiation has been produced after the laser action and the transition from glass to glass ceramic has
been completed. 相似文献
7.
An optical clock based on an Er3+ fiber femtosecond laser and a two-mode He–Ne/CH4 optical frequency standard (λ=3.39 μm) is realized. Difference-frequency generation is used to down convert the 1.5-μm frequency comb of the Er3+ femtosecond laser to the 3.4-μm range. The generated infrared comb overlaps with the He–Ne/CH4 laser wavelength and does not depend on the carrier–envelope offset frequency of the 1.5-μm comb. In this way a direct phase-coherent
connection between the optical frequency of the He–Ne/CH4 standard and the radio frequency pulse repetition rate of the fiber laser is established. The stability of the optical clock
is measured against a commercial hydrogen maser. The measured relative instability is 1×10−12 at 1 s and for averaging times less than 50 s it is determined by the microwave standard, while for longer times a drift
of the He–Ne/CH4 optical standard is dominant. 相似文献
8.
Amin Abdolvand Robert W. Lloyd Marc J. J. Schmidt David J. Whitehead Zhu Liu Lin Li 《Applied Physics A: Materials Science & Processing》2009,95(2):447-452
We present results on the growth of highly organised, reproducible, periodic microstructure arrays on a stainless steel substrate
using multi-pulsed Nd:YAG (wavelength of 1064 nm, pulse duration of 7 ns, repetition rate of 25 kHz, beam quality factor of
M
2∼1.5) laser irradiation in standard atmospheric environment (room temperature and normal pressure) with laser spot diameter
of the target being ∼50 μm. The target surface was irradiated at laser fluence of ∼2.2 J/cm2 and intensity of ∼0.31×109 W/cm2, resulting in the controllable generation of arrays of microstructures with average periods ranging from ∼30 to ∼70 μm, depending
on the hatching overlap between the consecutive scans. The received tips of the structures were either below or at the level
of the original substrate surface, depending on the experimental conditions. The peculiarity of our work is on the utilised
approach for scanning the laser beam over the surface. A possible mechanism for the formation of the structures is proposed. 相似文献
9.
Laser ablation of titanium and silicon targets immersed in liquid nitrogen was carried out using a YAG laser at 1.06 μm. Synthesized
particles were collected and were characterized by TEM, SEM, EDS, XRD, and XPS. In the case of a titanium target, the synthesized
particles had an atomic ratio of N/Ti=0.4 and a polycrystalline structure with many XRD peaks of TiN. This result indicates
the usefulness of laser ablation in liquid nitrogen for synthesizing nitrides. On the other hand, in the case of a silicon
target, the nitridation of the synthesized particles was negligible, and the synthesized particles had a polycrystalline structure
of pure cubic silicon. This means that the oxygen-free environment realized by liquid nitrogen is useful for synthesizing
particles with negligible oxidation. 相似文献
10.
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
11.
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
12.
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
13.
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
14.
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
15.
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
16.
We describe a new technique to measure the UV/visible absorption spectrum of the ablated material during the laser pulse.
The technique utilizes the continuum emission from one laser produced plasma as a light source to measure the absorption properties
of a second laser produced plasma which is formed on a semi-transparent target with an array of 40 μm holes. A 6 ns, 1064
nm laser was used to ablate a Ag target and the plasma absorption was measured in the range 450–625 nm for a laser fluence
of 1 J cm−2. The total absorption cross-section is (0.5–1.5)×10−17 cm2 in the range 450–540 nm. By comparing the measured absorption with a calculation using the plasma spectroscopy code FLYCHK
it can be concluded that, in the wavelength region examined here, the absorption is mainly due to bound-bound transitions. 相似文献
17.
D. Nakamura J. Nishimura T. Okada 《Applied Physics A: Materials Science & Processing》2008,92(4):813-816
The dynamics of the microplasmas created at a transparent solid–solid interface were investigated extensively. Microplasmas
were generated at an interface between a carbon (C) or a germanium (Ge) target and a SiO2 substrate by irradiating a KrF excimer laser beam onto the target, and the dynamics of the plasmas were investigated with
the aid of optical emission spectroscopy. Although the emission spectra that contained the characteristic emission lines and
the absorption bands originated from C and Ge species were observed from the C and Ge plasmas without the SiO2 substrate, identical spectra were obtained from both the plasmas created at the C–SiO2 and Ge–SiO2 interfaces. Furthermore, the target and the Si substrate surfaces were examined with a scanning electron microscope. The
SiO2 substrate was smoothly etched and a nanostructure of a chain-like morphology was also observed in the deposits on the SiO2 substrate. 相似文献
18.
A. A. Serafetinides M. Makropoulou E. Fabrikesi E. Spyratou C. Bacharis R. R. Thomson A. K. Kar 《Applied Physics A: Materials Science & Processing》2008,93(1):111-116
The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials,
techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive
aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular
lenses, and thus provide an alternative to conventional techniques. Ablation experiments were conducted using various polymer
substrates (PMMA samples, hydrophobic acrylic IOL, yellow azo dye doped IOL, and hydrophilic acrylic IOL consist of 25% H2O). The irradiation was performed using 100 fs pulses of 800 nm radiation from a regeneratively amplified Ti:sapphire laser
system. We investigated the ablation efficiency and the phenomenology of the ablated patterns by probing the ablation depth
using a profilometer. The surface modification was examined using a high resolution optical microscope (IOLs) or atomic force
microscope—AFM (PMMA samples). It was found that different polymers exhibited different ablation characteristics, a result
that we attribute to the differing optical properties of the materials. In particular, it was observed that the topography
of the ablation tracks created on the hydrophilic intraocular lenses was smoother in comparison to those created on the PMMA
and hydrophobic lens. The yellow doped hydrophobic intraocular lenses show higher ablation efficiency than undoped hydrophobic
acrylic lenses. 相似文献
19.
Petr Šmejkal Jiří Pfleger Blanka Vlčková 《Applied Physics A: Materials Science & Processing》2008,93(4):973-976
Laser fragmentation of Ag nanoparticles in Ag hydrosol was studied by simultaneous measurements of the transmitted fluence
of the incident laser beam and the time evolution of the surface plasmon extinction (SPE) spectra. The experiments showed
that the laser fragmentation in a small volume of hydrosol proceeds during first 20 pulses and then reaches saturation. The
value of the transmitted fluence corresponding to saturation increases with incident pulse fluence, but the impact of the
first pulse applied to the hydrosols shows an optical limitation. Fluences above 303 mJ/cm2 cause the formation of less stable, aggregating nanoparticles, while fluences below 90 mJ/cm2 do not provide sufficient energy for efficient fragmentation. The interval of fluences between 90–303 mJ/cm2 is optimal for fragmentation, since stable hydrosols constituted by small, non-aggregated nanoparticles are formed. 相似文献
20.
P. E. Dyer C. D. Walton R. Zakaria 《Applied Physics A: Materials Science & Processing》2009,95(2):319-323
Conical structures formed in 157 nm laser-ablated polycarbonate exhibit a well-defined fringe structure with a period of a
few 100 nm surrounding the cone base. Experiments and modelling studies of the interference produced by these micro-conical
mirrors are shown to provide a means of measuring the spatial coherence of the highly multi-mode 157 nm laser. 相似文献