共查询到20条相似文献,搜索用时 15 毫秒
1.
Kiyotaka Miura Kazuyuki Hirao Yasuhiko Shimotsuma Masaaki Sakakura Shingo Kanehira 《Applied Physics A: Materials Science & Processing》2008,93(1):183-188
Mixing metallic Al into the starting material for silicate glass is proposed as a means of forming Si structures in glass.
We confirmed that Si nanocrystals are space-selectively deposited in silicate glass via a thermite reaction triggered by femtosecond
laser pulses. Small Si particles were transformed into larger, but still micrometer sized, Si particles by laser irradiation.
These structures grew to micro-size particles due to the thermite reaction promoted by heat treatment. We discuss what effect
the irradiation of the focused laser pulse had on the Si deposition process in the laser-irradiated region. Localized high
temperatures and pressures and generation of shock waves appear to be very important in forming Si-rich structures that contribute
to the growth of Si particles. The diffusion of calcium ions by the generation of shock waves and the presence of Al-rich
structures is important for forming Si-rich structures such as Si clusters, which is achieved by continuously breaking Si–O
bonds using localized high temperatures. 相似文献
2.
S. Gaspard M. Oujja R. de Nalda M. Castillejo L. Bañares S. Lazare R. Bonneau 《Applied Physics A: Materials Science & Processing》2008,93(1):209-213
We have recently shown that irradiation of self-standing films of the biopolymers collagen and gelatine with single femtosecond
laser pulses produces a nanofoaming layer with regular bubble size which can be controlled by wavelength selection. Following
these initial studies, here we report on the temporal evolution of the foaming effect by measurements in situ and in real
time of the change in the transmittance of a cw probe HeNe laser through the irradiated films. Self standing films of the
biopolymers were irradiated with 90 fs laser pulses at 800, 400, and 266 nm. For fluences below and above the modification
threshold a permanent attenuation of the transmission occurs (increasing with fluence). The initial decay of the transmission
is fast (around few tens of ns), and is followed by dynamics in the longer timescale (micro and milliseconds). The temporal
evolution of the transmission measured upon fs laser irradiation is similar with that determined in the irradiation of the
biopolymer films at 248 nm with 25 ns laser pulses. The method allows separating in time the different processes occurring
after irradiation that lead to a permanent nanofoaming structure, while the results allow us to understand the mechanisms
of femtosecond laser processing of the biopolymers and their interest in biomedical applications. 相似文献
3.
Multilayer optical memory using femtosecond-laser induced fluorescence in rare-earth ion doped glass
Ki-Soo Lim Jongho Shin Kyungsik Jang Sunkyun Lee Douglas S. Hamilton 《Applied Physics A: Materials Science & Processing》2008,93(1):215-218
We report three-dimensional fluorescent memory by recording optical bits with irradiation of femtosecond laser pulses at 800 nm
and by reading photoluminescence change in Eu3+ doped glass. We produced multi-layered micro-bit patterns and read the blue emission from the 405 and 325 nm excitations
due to permanent reduction of Eu3+ to Eu2+ in sodium borate glass by scanning the irradiated region in multilayers. 相似文献
4.
Florenta Costache Sebastian Eckert Jürgen Reif 《Applied Physics A: Materials Science & Processing》2008,92(4):897-902
We study the modification of fluoride single crystals after irradiation with femtosecond laser pulses for a range of incident
intensities from well below to near damage threshold. The behavior of the desorbed positive ion yields, as analyzed by time-of-flight
mass spectrometry, is corroborated with temporal characteristics of radiation induced defects in fluorides.
The ion yield evolution upon repetitive irradiation (incubation) exhibits the typical reduction of the multi-shot damage threshold
with increasing number of pulses. The experimental data point towards an exponential growth of the transient defect density
as the origin of this effect. On the other hand, measurements of the time decay of transient defect fluorescence inside the
transparent sample show that the defect lifetime may be even longer than tens of milliseconds.
To account for the incubation and the increase of the radiation-target coupling efficiency, a model relating the defect lifetime
to a pulse-by-pulse accumulation of transient defects is presented, based on a calculation of the free electron density. 相似文献
5.
Bing Liu Zhendong Hu Yong Che Arnold Allenic Kai Sun Xiaoqing Pan 《Applied Physics A: Materials Science & Processing》2008,93(3):813-818
In this work, we study the application of ultrafast pulsed laser deposition (PLD) in ZnO nanomaterial synthesis, including
nanoparticles and nanorods. PLD using long pulse (nanosecond) lasers has been widely used as a method for growing prototype
materials. The recently-emerged ultrafast PLD is expected to be able to overcome the problem of large liquid droplet formation.
Using near infrared and femtosecond laser pulses in ablation, we first characterize the ablation plume using a Langmuir probe
and plasma optical emission spectroscopy. We then examine the structural properties of the nanoparticles generated during
low-fluence ablation. Finally, we demonstrate that using nanoparticle aggregates as templates, assisted by plume-excited nitrogen
radicals at a high fluence, high quality ZnO nanorods can be grown free of metal catalysts. 相似文献
6.
G. Lengl A. Plettl P. Ziemann J.P. Spatz M. Möller 《Applied Physics A: Materials Science & Processing》2001,72(6):679-685
Diblock-copolymers (PS(1700)-b-P2VP(450) or PS(1350)-b-P2VP(400)) forming spherical micelles, can be loaded with a Au-salt
and deposited on top of various substrates. Such polymer films have been exposed to a pulsed ArF excimer laser in order to
remove the polymer matrix and, in parallel, to chemically reduce the salt into metallic Au nanodots. To analyze this process
in detail, it was subdivided into three steps: (a) laser ablation of thick and thin diblock-copolymer films; (b) laser irradiation
of Au-salt loaded diblock-copolymer films; and (c) laser irradiation of arrays of metallic Au nanodots. In (a) it was found
that a complete removal of the polymer by laser ablation is only possible in air under ambient conditions while identical
laser irradiations under vacuum result in a residual layer of approximately 14 nm. Substep (b) revealed a nucleation process
of the resulting metallic Au within the micellar core leading to clusters of small Au dots. Furthermore, this substep provided
evidence for an asymmetric interplay between the macroscopic temperature of a polymer film during laser treatment and the
energy density per laser pulse. In (c) it could be demonstrated that metallic Au nanodots on mica are stable against laser
irradiation under conditions leading to a polymer removal.
Received: 7 August 2000 / Accepted: 2 November 2000 / Published online: 3 April 2001 相似文献
7.
N. Sanner O. Utéza B. Bussiere G. Coustillier A. Leray T. Itina M. Sentis 《Applied Physics A: Materials Science & Processing》2009,94(4):889-897
The paper is focused on the importance of accurate determination of surface damage/ablation threshold of a dielectric material
irradiated with femtosecond laser pulses. We show that different damage characterization techniques and data treatment procedures
from a single experiment provide complementary physical results characterizing laser–matter interaction. We thus compare and
discuss two regression techniques, well adapted to the measurement of laser ablation threshold, and a statistical approach
giving the laser damage threshold and further information concerning the deterministic character of femtosecond damage. These
two measurements are crucial for laser micromachining processes and high peak-power laser technology in general. 相似文献
8.
J. T. Dickinson 《Applied Physics A: Materials Science & Processing》2008,92(4):1025-1030
Below laser fluences where a plasma is formed (the so-called plasma or plume formation threshold) a number of fundamental
phenomena can occur where particles such as atomic and molecular ions, atoms and molecular neutrals, and electrons can be
emitted. An understanding of such processes is necessary to develop predictive models for material removal from laser irradiated
surfaces—at the foundation of laser etching, machining, and pulsed laser deposition. We have reported on a number of the mechanisms
for such emission processes. Here, due to space limitations, we present a summary of our studies on the formation of negative
alkali ions from single crystal KCl during exposure to pulsed 248-nm radiation at fluences well below the threshold for plasma
formation. Despite the high electron affinities of the corresponding halogen atoms, negative halogen ions were not detected.
Significantly, the positive and negative alkali ion distributions overlap strongly in time and space, consistent with K formation
by the sequential attachment of two electrons to K+. Negative alkali ions are also observed under comparable conditions from LiF, NaCl, and KBr. In each material, the strong
overlap between the positive and negative alkali ion distributions, and the lack of detected negative halogen ions, suggest
that negative ion formation involves a similar mechanism. 相似文献
9.
Yang Yang Jianjun Yang Chunyong Liang Hongshui Wang Xiaonong Zhu Dengfeng Kuang Yong Yang 《Applied Physics A: Materials Science & Processing》2008,92(3):635-642
Generation of self-organized sub-wavelength surface structures on a nickel–titanium alloy plate by femtosecond laser pulses
is investigated experimentally through line-scribing experiments in air. It is found that Bragg-like relief gratings, with
the orientation perpendicular to the laser polarization, are formed over the entire laser-scribed regions. The average period
is measured as 630±30 nm. Distinctive features of these novel surface structures include nanoparticle-covered grating ridges
and the maintainable spatial period regardless of incidence angles. With different laser parameters and sample scan speeds,
sub-wavelength grating structures can evolve into cellular-like nanotextures. Optimal conditions for forming these surface
structures are determined in terms of laser energy and scan speed. Elementary analyses of the structured surfaces by X-ray
diffraction and photoelectron spectroscopy reveal that both the crystal structures and the chemical elements can remain in
their original states, but the surface grains are refined and the atomic percentages are varied after femtosecond laser treatments. 相似文献
10.
F. Lahoz P. Haro-Gonzalez F. Rivera-López S. González-Pérez I. R. Martín N. E. Capuj C. N. Afonso J. Gonzalo J. Fernández R. Balda 《Applied Physics A: Materials Science & Processing》2008,93(3):621-625
Thin films of Er3+-doped lead–niobium germanate have been produced by pulsed laser deposition from Er3+-doped 25PbO2–25Nb2O5–50GeO2 (mol%) transparent glasses with an Er content in the range 0.5–3 wt%. The room-temperature infrared to visible upconversion
properties of these thin films have been investigated under 800-nm laser excitation. An energy transfer upconversion mechanism
has been identified to be responsible for the population of the 4S3/2:2H11/2 excited level, from which an intense green emission occurs. A rate equation analysis supports the proposed mechanism. 相似文献
11.
The mechanism of nanobump formation in femtosecond pulse laser nanostructuring of thin metal films 总被引:1,自引:0,他引:1
Dmitriy S. Ivanov Baerbel Rethfeld Gerard M. O’Connor Thomas J. Glynn Alexey N. Volkov Leonid V. Zhigilei 《Applied Physics A: Materials Science & Processing》2008,92(4):791-796
The physical mechanisms responsible for the formation of nanobump structures on a surface of a thin metal film irradiated
by a tightly focused femtosecond laser pulse are investigated in a large-scale molecular dynamics simulation. The simulation
is performed with a combined atomistic-continuum model adapted for an adequate representation of laser-induced processes at
the length-scale of the entire laser spot. The relaxation of the compressive stresses generated by the fast laser heating
is identified as the main driving force responsible for the separation of the metal film from the substrate and formation
of the nanobump. The kinetics of the transient melting and resolidification, occurring under conditions of the fast cooling
due to the two-dimensional electron heat conduction, defines the shape of the nanobump. The predictions of the simulation
are related to the surface structures observed in femtosecond laser nanostructuring. 相似文献
12.
A. Stalmashonak A. Podlipensky G. Seifert H. Graener 《Applied physics. B, Lasers and optics》2009,94(3):459-465
The shapes of initially spherical Ag nanoparticles in soda-lime glass are persistently changed using fs laser irradiation.
With linearly polarized pulses, this shape transformation of the nanoparticles causes optical dichroism of the material. The
intensity dependence of this effect is studied comprehensively, addressing the whole intensity range of permanent modifications
as well as the influence of the number of laser pulses applied to one spot on the sample. The results are used as basis to
develop a complete scenario of the possible mechanisms leading to the laser-induced shape transformation of metallic nanoparticles
in glass. 相似文献
13.
Feng Ren Xiang Heng Xiao Guang Xu Cai Jian Bo Wang Chang Zhong Jiang 《Applied Physics A: Materials Science & Processing》2009,96(2):317-325
In this paper, we summarize our recent results of study on how to engineer the embedded metal nanoparticles in silica by ion
implantation and ion irradiation technologies, including controlling the size, distribution and morphology of nanoparticles.
The optical properties of the tailored nanoparticle composites are studied. Thermal annealing, electron beam irradiation,
and chemical erosion are used to study the stability of these embedded nanoparticles by ex situ or in situ transmission electron
microscopy observation. 相似文献
14.
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
15.
Guodong Wei Weiping Qin Ryongjin Kim Guofeng Wang Peifen Zhu Daisheng Zhang Kezhi Zheng Lili Wang 《Applied Physics A: Materials Science & Processing》2009,96(2):521-527
By using a novel and low-cost microwave method, three-dimensional SiC networks have been synthesized in large-scale. The composition
and structural features of the product were characterized by X-ray diffraction, field emission scanning electron microscopy,
and transmission electron microscopy. The results show that the SiC networks consist of nanocable X-junction and Y-junction.
Some nanocables are composed of 3C–SiC multicore encapsulated in single amorphous SiO2 shell. The SiC networks emitted stable violet–blue light around 380 nm under 325-nm excitation. Compared to the emission
peak of the SiC networks after etched and the reported results of 3C–SiC nanowires, the emission peak of the SiC networks
shows significant blueshift. The origin of the photoluminescence for the SiC networks could be due to two possible reasons:
the central crystalline SiC nanowires and amorphous SiO2 shell. A two-step growth mechanism of the SiC networks was proposed based on the experimental characterizations. The successful
synthesis of SiC networks is an important step in the development of SiC-based electronic devices and circuits. 相似文献
16.
Ch. Wennemann W. -D. Schmidt-Ott T. Hild K. Krumbholz V. Kunze F. Meissner H. Keller R. Kirchner E. Roeckl 《Zeitschrift für Physik A Hadrons and Nuclei》1994,347(3):185-189
Using a208Pb beam of the UNILAC accelerator at GSI we produced the new isotopes203Au and205Au and identified them by measuring their-decay properties. Their half-lives were found to be 60(6)s and 31(2)s, respectively, and theQ-value of203Au was determined to beQ
=2040(60)keV. Nuclear structure information of203,205Hg was derived from this measurement. Furthermore, production cross-sections of203,205Au are given and compared to those obtained in other experiments.This work has been supported by the Federal Ministry for Research and Technology (BMFT) under contract number 06 Gö 451-1/2 相似文献
17.
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
18.
Shingo Kanehira Kiyotaka Miura Kazuyuki Hirao Naoya Shibata Yuichi Ikuhara 《Applied Physics A: Materials Science & Processing》2008,92(4):913-916
We show a unique technique to form dense dislocations locally inside a MgO single crystal with a rock-salt type structure
using femtosecond (fs) laser irradiation. Cross-shaped patterns of micrometer size, originating from densely introduced dislocations,
are formed spontaneously around the focal point. We controlled the three-dimensional propagation of the dislocations by adjusting
the pulse energy of the fs laser and NA of objective lens. The technique may open up a new field of dislocation technology
for optical applications. 相似文献
19.
D. Lambrecht T. Blaich T. W. Elze H. Emling H. Freiesleben K. Grimm W. Henning R. Holzmann J. G. Keller H. Klingler J. V. Kratz R. Kulessa S. Lange Y. Leifels E. Lubkiewicz E. F. Moore W. Prokopowicz R. Schmidt C. Schütter H. Spies K. Stelzer J. Stroth E. Wajda W. Waluś M. Zinser E. Zude 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):115-120
We investigate the beam energy dependence of neutron and proton squeeze-out in collisions of197Au+197Au atE/A=400—800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve — independent of beam energy — if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile.
The members of the FOPI-collaboration: J.P. Alard, Z. Basrak, N. Bastid, I.M. Belayev, M. Bini, R. Bock, A. Buta, R. aplar, C. Cerruti, N. Cindro, J.P. Coffin, M. Crouau, P. Dupieux, J. Erö, Z.G. Fan, P. Fintz, Z. Fodor, R. Freifelder, L. Fraysse, S. Frolov, A. Gobbi, Y. Grigorian, G. Guillaume, N. Herrmann, K.D. Hildenbrand, S. Hölbling, O. Houari, S.C. Jeong, M. Jorio, F. Jundt, J. Kecskemeti, P. Koncz, Y. Korchagin, R. Kotte, M. Krämer, C. Kuhn, I. Legrand, A. Lebedev, C. Maguire, V. Manko, T. Matulewicz, G. Mgebrishvili, J. Mösner, D. Moisa, G. Montarou, P. Morel, W. Neubert, A. Olmi, G. Pasquali, D. Pelte, M. Petrovici, G. Poggi, F. Rami, W. Reisdorf, A. Sadchikov, D. Schüll, Z. Seres, B. Sikora, V. Simion, S. Smolyankin, U. Sodan, N. Taccetti, K. Teh, R. Tezkratt, M. Trzaska, M.A. Vasiliev, P. Wagner, J.P. Wessels, T. Wienold, Z. Wilhelmi, D. Wohlfarth, A.V. Zhilin. 相似文献