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1.
Different surface morphologies on AISI 304 stainless steel have been obtained after millisecond Nd:YAG pulsed laser oxidation. The effects of laser processing parameters, especially pulse width and laser energy density on the surface morphologies of the stainless steel were emphatically investigated. The results showed that surface morphologies were significantly changed with increasing laser pulse widths and laser energy densities. When the pulse width was 0.2–1.0 ms and laser energy density was 4.30×106–7.00×106 J/m2, the surface was obviously damaged and the morphologies varied gradually from craters to ripple structures. However, when the pulse width was longer than 1 ms and the laser energy density was increased from 1.90×107 to 3.16×107 J/m2, the sizes of craters got smaller until disappeared and the surface became flatter and smoother. Nevertheless, the smooth surface was not obtained under overhigh laser energy densities. In addition, the schematic relationship was used to describe the formation process and mechanism of different surface morphologies. 相似文献
2.
The use of ultrashort laser pulses is a way to increase recoil momentum under laser ablation of materials, because, in this case, the energy deposition per unit volume of the target material is substantially higher due to reduced heat dissipation. By using methods of combined interferometry, we estimated the specific impulse (~200–900 s), momentum coupling coefficient (~2 × 10?5?3 × 10?4 Ns/J), laser-energy conversion efficiency to kinetic energy of the gas-plasma flow (~0.05–0.82), and degree of the gas-plasma flow monochromaticity (~0.72–0.92) under femtosecond (τ ~ 45 fs, λ ~ 800 nm) ablation of refractory metals (Ti, Zr, Mo, and Nb) in vacuum. 相似文献
3.
2 laser using a miniature water spray is demonstrated. An ablation threshold of 1.4 J/cm2, an optimal energy density of 9–10 J/cm2, and a corresponding specific ablation energy of 25–30 J/mm3 are found for pig thighbone compacta at λ=9.57 μm and a beam waist diameter of 0.5 mm. The water spray alleviates tissue
carbonization even at high laser pulse repetition rates and increases ablation efficiency.
Received: 9 March 1998/Revised version: 6 July 1998 相似文献
4.
W.M. Shu Y. Kawakubo M.F. Nishi 《Applied Physics A: Materials Science & Processing》2003,76(3):421-425
Recovery of tritium from co-deposited layers formed in deuterium–tritium plasma operations of the TFTR (Tokamak Fusion Test
Reactor) was investigated by the use of an ArF excimer laser operating at the wavelength of 193 nm. At the laser energy density
of 0.1 J/cm2, a transient spike of the tritium-release rate was observed at initial irradiation. Hydrogen isotopes were released in the
form of hydrogen-isotope molecules during the laser irradiation in vacuum, suggesting that tritium can be recovered readily
from the released gases. In a second experiment, hydrogen (tritium) recovery from the co-deposited layers on JT-60 tiles that
had experienced hydrogen-plasma operations was investigated by laser ablation with a focused beam of the excimer laser. The
removal rate of the co-deposited layers was quite low when the laser energy density was smaller than the ablation threshold
(1.0 J/cm2), but reached 1.1 μm/pulse at the laser energy density of 7.6 J/cm2. The effective absorption coefficient in the co-deposited layers at the laser wavelength was determined to be 1.9 μm-1. The temperature of the surface during the irradiation at the laser energy density of 0.5 J/cm2 was measured on the basis of Planck’s law of radiation, and the maximum temperature during the irradiation decreased from
3570 K at the initial irradiation to 2550 K at the 1000th pulse of the irradiation.
Received: 5 August 2002 / Accepted: 7 August 2002 / Published online: 28 October 2002
RID="*"
ID="*"Corresponding author. Fax: +81-29/2825917, E-mail: shu@tpl.tokai.jaeri.go.jp 相似文献
5.
6.
C. K. Chung M. W. Liao S. L. Lin 《Applied Physics A: Materials Science & Processing》2010,99(1):285-290
Pyrex glass etching using laser ablation is an important technology for the microfluid application to lab-on-a-chip devices
but suffers from the formation of surface crack. In this article, the addition of nonionic surfactant to water for glass ablation
using water-assisted CO2 laser processing (WACLAP) has been investigated to enhance ablation rate and to eliminate conventional surface defects of
cracks in air. WACLAP for Pyrex glass ablation can reduce thermal-stress-induced crack with water cooling and hydrophilic
nonionic surfactant to water can enhance ablation performance. Compared to pure water, the 15% weight percent Lauramidopropyl
Betaine surfactant solutions for WACLAP can enhance ablation rate from 13.6 to 25 μm/pass of Pyrex glass ablation at a linear
laser energy density of 2.11 J/cm, i.e., 24 W power, 114 mm/s scanning speed, and obtain through-wafer etching at 3.16 J/cm
for 20 passes without cracks on the surface. Effect of surfactant concentration and linear energy density on WACLAP was also
examined. The possible mechanism of surfactant-enhanced phenomenon was discussed by the Newton’s law of viscosity of surfactant
solution. 相似文献
7.
P.W. Leech A.S. Holland S. Sriram M. Bhaskaran 《Applied Physics A: Materials Science & Processing》2008,91(4):679-684
The patterning of lanthanum-doped lead zirconate titanate (PLZT) and strontium-doped lead zirconate titanate (PSZT) thin films
has been examined using a 5-ns pulsed excimer laser. Both types of film were deposited by rf magnetron sputtering with in
situ heating and a controlled cooling rate in order to obtain the perovskite-structured films. The depth of laser ablation
in both PSZT and PLZT films showed a logarithmic dependence on fluence. The ablation rate of PLZT films was slightly higher
than that of PSZT films over the range of fluence (10–150 J/cm2) and increased linearly with number of pulses. The threshold fluence required to initiate ablation was ∼ 1.25 J/cm2 for PLZT and ∼ 1.87 J/cm2 for PSZT films. Individual squares were patterned with areas ranging from 10×10 μm2 up to 30×30 μm2 using single and multiple pulses. The morphology of the etched surfaces comprised globules which had diameters of 200–250 nm
in PLZT and 1400 nm in PSZT films. The diameter of the globules has been shown to increase with fluence until reaching an
approximately constant size at ≤ 20 J/cm2 in both types of film. The composition of the films following ablation has been compared using X-ray photoelectron spectroscopy
and energy-dispersive X-ray spectroscopy.
PACS 79.20.Ds; 82.80.Pv; 82.80.Ej 相似文献
8.
为研究激光烧蚀靶产生冲量过程和机理, 建立了一个复杂的一维热传导和流体动力学模型. 以空间碎片常见材料Al为例, 用建立的模型数值计算了纳秒脉宽激光烧蚀靶产生的冲量及冲量耦合系数随时间变化情况. 数值结果和已有的实验数据符合的较好. 数值计算表明: 激光脉冲时间内, 靶获得的冲量随时间迅速增加, 在脉冲时间结束后, 冲量变化随时间趋于稳定; 在冲量耦合过程中, 烧蚀等离子体向真空膨胀, 羽流尺度逐渐增大, 同时吸收入射激光能量, 导致激光与靶耦合的能量降低.
关键词:
激光烧蚀
冲量耦合
等离子体 相似文献
9.
We investigate laser pulse influence on aluminum target in irradiance range 109 to 1016 W/cm2, pulse duration between 10−8 and 10−15 s, Gaussian time profile with wavelength of 0.8 μm. For all computations energy density was 10 J/cm2. Plasma in the evaporated material is generated at the energy density above 10 J/cm2as the modeling showed.Long and short laser pulses distinguish by the mechanisms of energy transformation. For short laser pulses there is volumetric energy absorption, together with rapid phase transitions it lead to overheating in solid and liquid states, overheated solid temperature rises up to (6-8)Tm. Under influence of the energy saved in overheated solid, duration of the phase transitions becomes nanosecond, which is several orders of magnitude longer than laser pulse. 相似文献
10.
N. G. Semaltianos S. Logothetidis W. Perrie S. Romani R. J. Potter S. P. Edwardson P. French M. Sharp G. Dearden K. G. Watkins 《Journal of nanoparticle research》2010,12(2):573-580
Silicon nanoparticles were generated by femtosecond laser [387 nm, 180 fs, 1 kHz, pulse energy = 3.5 μJ (fluence = 0.8 J/cm2)] ablation of silicon in deionized water. Nanoparticles with diameters from ~5 up to ~200 nm were observed to be formed in
the colloidal solution. Their size distribution follows log-normal function with statistical median diameter of ≈20 nm. Longer
ablation time leads to a narrowing of the nanoparticle size distribution due to the interaction of the ablating laser beam
with the produced nanoparticles. Raman spectroscopy measurements confirm that the nanoparticles exhibit phonon quantum confinement
effects and indicate that under the present conditions of ablation they are partially amorphous. 相似文献
11.
Enrique Camps L. Escobar-Alarcón V. H. Castrejón-Sánchez P. Tolentino-Eslava 《Applied Physics A: Materials Science & Processing》2008,93(3):759-763
Amorphous carbon thin films were deposited by laser ablation of a graphite target, using the fundamental line of a 5 ns Nd:YAG
laser. Deposition was carried out as a function of the plasma parameters (mean kinetic ion energy and plasma density), determined
by means of a planar probe. In the selected working regimes the optical emission from the plasma is mainly due to atomic species,
namely C+ (426.5 nm); however, there is also emission from other atomic species and molecular carbon. The hardness and resistivity
could be varied in the range between 10 and 25 GPa, and 108 and 1011 Ω cm, respectively. The maximum values were obtained at a 200 eV ion energy and 6×1013 cm−3 plasma density, where the maximum quantity of C–C sp3 bonds was formed, as confirmed by Raman spectroscopy. 相似文献
12.
Xiaobo Yang Nengli Dai Hua Long Peixiang Lu Wan Li Fagang Jiang 《Optics and Lasers in Engineering》2010,48(7-8):806-810
Femtosecond laser technology, used as a minimally invasive tool in intrastromal refractive surgery, may also have potential as a useful instrument for glaucoma filtration surgery. The purpose of the present study was to evaluate the feasibility of minimally invasive laser sclerostomy by femtosecond laser photodisruption and seek the appropriate patterns of laser ablation and relevant laser parameters. A femtosecond laser (800 nm/50 fs/1 kHz), focused by a 0.1 numerical aperture (NA) objective lens, with different pulse energies and exposure times was applied to ablate hydrated rabbit sclera in vitro. The irradiated samples were examined by scanning electron microscopy (SEM). By moving a three-dimensional, computer-controlled translation stage to which the sample was attached, the femtosecond laser could produce three types of ablation patterns, including linear ablation, cylindrical aperture and rectangular cavity. With pulse energies ranging from 37.5 to 150 μJ, the linear lesions were consistently observed at the inner surface of sclera, whereas it failed to make any photodisruption if pulse energy was below the threshold value of 31.25 μJ, with the corresponding threshold intensity of 4.06×1014 W/cm2. The depths of the linear lesions increased linearly with both pulse energy (37.5–150 μJ) and exposure time (0.1–0.4 s). Histological examination showed the incisions produced by femtosecond laser photodisruption had precise geometry and the edges were sharp and smooth, with no evidence of collateral damage to the surrounding tissue. Our results predict the potential application of femtosecond laser pulses in minimally invasive laser sclerostomy for glaucoma treatment. 相似文献
13.
Sonja Hermann Nils-Peter Harder Rolf Brendel Dirk Herzog Heinz Haferkamp 《Applied Physics A: Materials Science & Processing》2010,99(1):151-158
In this work, we report on laser ablation of thermally grown SiO2 layers from silicon wafer substrates, employing an 8–9 ps laser, at 1064 (IR), 532 (VIS) and 355 nm (UV) wavelengths. High-intensity
short-pulse laser radiation allows direct absorption in materials with bandgaps higher than the photon energy. However, our
experiments show that in the intensity range of our laser pulses (peak intensities of <2×1012 W/cm2) the removal of the SiO2 layer from silicon wafers does not occur by direct absorption in the SiO2 layer. Instead, we find that the layer is removed by a “lift off” mechanism, actuated by the melting and vaporisation of
the absorbing silicon substrate. Furthermore, we find that exceeding the Si melting threshold is not sufficient to remove
the SiO2 layer. A second threshold exists for breaking of the layer caused by sufficient vapour pressure. For SiO2 layer ablation, we determine layer thickness dependent minimum fluences of 0.7–1.2 J/cm2 for IR, 0.1–0.35 J/cm2 for VIS and 0.2–0.4 J/cm2 for UV wavelength. After correcting the fluences by the reflected laser power, we show that, in contrast to the melting threshold,
the threshold for breaking the layer depends on the SiO2 thickness. 相似文献
14.
Ultrafast pulsed laser ablation has been investigated as a technique to machine CdWO4 single crystal scintillator and segment it into small blocks with the aim of fabricating a 2D high energy X-ray imaging array. Cadmium tungstate (CdWO4) is a brittle transparent scintillator used for the detection of high energy X-rays and γ-rays. A 6 W Yb:KGW Pharos-SP pulsed laser of wavelength 1028 nm was used with a tuneable pulse duration of 10 ps to 190 fs, repetition rate of up to 600 kHz and pulse energies of up to 1 mJ was employed. The effect of varying the pulse duration, pulse energy, pulse overlap and scan pattern on the laser induced damage to the crystals was investigated. A pulse duration of ≥500 fs was found to induce substantial cracking in the material. The laser induced damage was minimised using the following operating parameters: a pulse duration of 190 fs, fluence of 15.3 J cm−2 and employing a serpentine scan pattern with a normalised pulse overlap of 0.8. The surface of the ablated surfaces was studied using scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Ablation products were found to contain cadmium tungstate together with different cadmium and tungsten oxides. These laser ablation products could be removed using an ammonium hydroxide treatment. 相似文献
15.
S.E. Kirkwood A.C. van Popta Y.Y. Tsui R. Fedosejevs 《Applied Physics A: Materials Science & Processing》2005,81(4):729-735
The single-shot ablation threshold and incubation coefficient of copper were investigated using an amplified near-infrared, femtosecond Ti:sapphire laser. To date, the near-infrared femtosecond ablation threshold of copper has been reported in the range of several hundred millijoules per cm2 based primarily on multiple shot ablation studies. A careful study of the single shot ablation threshold for copper was carried out yielding an incident single-shot ablation threshold of (1.06±0.12) J/cm2 for a clean copper foil surface. This was determined by measuring the diameters of the ablation spots as a function of the laser pulse energy using scanning electron microscopy for spatially Gaussian laser spots. When multiple shots were taken on the same spot, a reduction in ablation threshold was observed, consistent with a multiple shot incubation coefficient of 0.76±0.02. Similar experiments on 250 nm and 500 nm copper thin films sputtered on a silicon substrate demonstrated that scaling the threshold values with the absorbance of energy at the surface yields a consistent absorbed fluence threshold for copper of (59±10) mJ/cm2. This absorbed threshold value is consistent with the expected value from a two-temperature model for the heating of copper with an electron-lattice coupling constant of g=1017 Wm-3 K-1. Single-shot rippling of the surface in the threshold ablation intensity regime was also observed for the foil target but not for the smooth thin film target. PACS 61.80.Ba; 61.82.Bg 相似文献
16.
M. Stanislawki J. Meister T. Mitra M.M. Ivanenko K. Zanger P. Hering 《Applied physics. B, Lasers and optics》2001,72(1):115-120
The Er:YAG and the CO2 laser are competitors in the field of hard tissue ablation. The use of Er:YAG lasers (2.94 μm, pulse length
L of 100 to 200 μs) show smaller areas of thermal defects then ‘‘superpulsed’’ CO2 lasers with pulse lengths of approximately 100 μs. Only the development of a Q-switched CO2 laser (9.6 μm, τL=250 ns) allowed for similar results. In this paper new results for the Er:YAG and the Q-switched CO2 laser under the influence of water spray will be presented. Several parameters are of special interest for these investigations:
the specific ablation energy, which shows a minimum for the CO2 laser at an energy density of 9 J/cm 2 and a broad shallow minimum in the range of 10 to 70 J/cm2 for the Er:YAG laser, and comparison of the cut-shape and depth. Surface effects and cutting velocity are discussed based
on SEM pictures.
Received: 19 July 2000 / Revised version: 1 November 2000 / Published online: 30 November 2000 相似文献
17.
N. G. Semaltianos W. Perrie J. Cheng P. French M. Sharp G. Dearden K. G. Watkins 《Applied Physics A: Materials Science & Processing》2010,98(2):345-355
Picosecond laser (10.4 ps, 1064 nm) ablation of the nickel-based superalloy C263 is investigated at different pulse repetition
rates (5, 10, 20, and 50 kHz). The two ablation regimes corresponding to ablation dominated by the optical penetration depth
at low fluences and of the electron thermal diffusion length at high fluences are clearly identified from the change of the
surface morphology of single pulse ablated craters (dimples) with fluence. The two corresponding thresholds were measured
as F
th(D1)1=0.68±0.02 J/cm2 and F
th(D2)1=2.64±0.27 J/cm2 from data of the crater diameters D
1,2 versus peak fluence. The surface morphology of macroscopic areas processed with a scanning laser beam at different fluences
is characterised by ripples at low fluences. As the fluence increases, randomly distributed areas among the ripples are formed
which appear featureless due to melting and joining of the ripples while at high fluences the whole irradiated surface becomes
grainy due to melting, splashing of the melt and subsequent resolidification. The throughput of ablation becomes maximal when
machining at high pulse repetition rates and with a relatively low fluence, while at the same time the surface roughness is
kept low. 相似文献
18.
19.
Diamond-like carbon (DLC) films were fabricated by pulsed laser ablation of a liquid target. During deposition process the growing films were exited by a laser beam irradiation. The films were deposited onto the fused silica using 248 nm KrF eximer laser at room temperature and 10−3 mbar pressure. Film irradiation was carried out by the same KrF laser operating periodically between the deposition and excitation regimes. Deposited DLC films were characterized by Raman scattering spectroscopy. The results obtained suggested that laser irradiation intensity has noticeable influence on the structure and hybridization of carbon atoms deposited. For materials deposited at moderate irradiation intensities a very high and sharp peak appeared at 1332 cm−1, characteristic of diamond crystals. At higher irradiation intensities the graphitization of the amorphous films was observed. Thus, at optimal energy density the individual sp3-hybridized carbon phase was deposited inside the amorphous carbon structure. Surface morphology for DLC has been analyzed using atomic force microscopy (AFM) indicating that more regular diamond cluster formation at optimal additional laser illumination conditions (∼20 mJ per impulse) is possible. 相似文献
20.
Ultrafast laser ablation of indium tin oxide thin films for organic light-emitting diode application
Mira Park Byong Hyok Chon Hyun Sun Kim Sae Chae Jeoung Dongho Kim Jeoung-Ik Lee Hye Yong Chu Hyeong Rae Kim 《Optics and Lasers in Engineering》2006,44(2):138-146
Ultrafast laser ablation of ITO thin film coated on the glass has been investigated as a function of laser fluence as well as the number of laser pulses. The ablation threshold of ITO thin film was found to be 0.07 J/cm2 that is much lower than that of glass substrate (about 1.2–1.6 J/cm2), which leads to a selective ablation of ITO film without damage on glass substrate. The changes in the electrical resistance and morphology of ablated trench of ITO electrode were found to be strongly dependent on the processing conditions. We present the performance of organic light-emitting diodes (OLED) fabricated with ITO electrode patterned by ultrafast laser ablation. 相似文献