共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Stenger S. Inouye D.M. Stamper-Kurn A.P. Chikkatur D.E. Pritchard W. Ketterle 《Applied physics. B, Lasers and optics》1999,69(5-6):347-352
Two sets of studies concerning the interaction of off-resonant light with a sodium Bose–Einstein condensate are described.
In the first set, properties of a Bose–Einstein condensate were studied using Bragg spectroscopy. The high momentum and energy
resolution of this method allowed a spectroscopic measurement of the mean-field energy and of the intrinsic momentum distribution
of the condensate. Depending on the momentum transfer, both the phonon regime as well as the free-particle regime could be
explored. In the second set of studies, the cigar-shaped condensate was exposed to a single off-resonant laser beam and highly
directional scattering of light and atoms was observed. This collective light scattering was caused by the long coherence
time of the quasi-particles in the condensate and resulted in a new form of matter wave amplification.
Received: 26 June 1999 / Revised version: 21 September 1999 / Published online: 10 November 1999 相似文献
2.
K. Sugioka K. Obata M.H. Hong D.J. Wu L.L. Wong Y.F. Lu T.C. Chong K. Midorikawa 《Applied Physics A: Materials Science & Processing》2003,77(2):251-257
Hybrid laser processing for the precision microfabrication of glass materials, in which the interaction of a conventional
pulsed laser beam and a medium on the material surface leads to effective ablation and modification, is reviewed. A major
role of the medium is to produce strong absorption of the conventional laser beam by the material. Simultaneous irradiation
by a vacuum ultraviolet (VUV) laser beam that possesses an extremely small laser fluence and an ultraviolet (UV) laser greatly
improves the ablation quality and modification efficiency for fused silica (VUV-UV multiwavelength excitation process). The
metal plasma generated by the laser beam effectively assists high-quality ablation of transparent materials by the same laser
beam, resulting in microstructuring, cutting, color marking, printing, and selective metallization of glass materials (laser-induced
plasma-assisted ablation (LIPAA)). The detailed discussion presented here includes the ablation mechanism of hybrid laser
processing.
Received: 18 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-48/462-4682, E-mail: ksugioka@postman.riken.go.jp 相似文献
3.
Laser polishing of diamond plates 总被引:5,自引:0,他引:5
S.M. Pimenov V.V. Kononenko V.G. Ralchenko V.I. Konov S. Gloor W. Lüthy H.P. Weber A.V. Khomich 《Applied Physics A: Materials Science & Processing》1999,69(1):81-88
Results are reported on laser polishing of 150–400-μm-thick free-standing diamond films with either a copper vapor laser (510 nm
wavelength) or an ArF excimer laser (193 nm wavelength). Studies were focused on three particular goals. First, we aimed at
a choice of optimum conditions for laser polishing of thick diamond films. It was shown that the laser polishing conditions
and the resulting surface roughness were controlled by varying the angle of incidence of a scanning laser beam and by polishing
time. Second, the laser ablation technique was applied to remove a defective layer from the “substrate” side of the diamond
plates in order to reduce optical losses due to absorption in this layer. Third, the structure of the laser-graphitized diamond
surface was studied using UV, visible, and IR optical spectroscopy techniques in the course of the “step-by-step” oxidative
removal of the graphitic layer with increasing temperature of the oxidation in ambient air. Once the graphitic layer was removed,
the optical transmission in the UV-visible-IR spectral range of the diamond films polished under optimum conditions was measured
and compared with the optical transmission of the mechanically polished diamond films. It was shown that the optical quality
(in the long-wave infrared region) of the laser-polished diamond plates was sufficient to reach the transmittance value very
close to the theoretical limit.
Received: 20 October 1998 / Accepted: 8 March 1999 / Published online: 5 May 1999 相似文献
4.
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
5.
Wilhelm Pfleging Robert KohlerMaika Torge Vanessa TrouilletFriederike Danneil Michael Stüber 《Applied Surface Science》2011,257(18):7907-7912
A flexible and rapid surface functionalization of amorphous carbon films shows a great potential for various application fields such as biological surfaces and tribological systems. For this purpose, the combination of thin film deposition and subsequent laser material processing was investigated. Amorphous carbon layers doped with hydrogen were deposited on silicon wafers by reactive direct-current magnetron sputtering. Films with three different hydrogen contents were synthesized. Subsequent to the thin film deposition process, UV laser material processing at wavelengths of 193 nm or 248 nm was performed with respect to chemical surface modification and surface structuring on micro- and nanometer scale. Depending on structure size and laser-induced chemical surface modification the adjustment of the surface energy and wetting behaviour in a broad range from hydrophobic to hydrophilic was possible. The chemical modification and the ablation mechanisms near the ablation threshold were strongly influenced by the hydrogen content in amorphous carbon thin films.Structural and chemical information of the as-deposited and modified films was obtained by Raman spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. 相似文献
6.
N. V. Volkov I. V. Oleinikov E. A. Anan’eva 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(2):236-239
The results of study of ion-cleaned and -implanted surfaces of polycrystalline Be, Al, Ti, Fe, Cu, Mo, Zr, and W using optical
and infrared (IR) spectroscopy are presented. It is shown that major changes in the optical reflectance spectra are observed
in the range of 190–250 nm and are associated with both the formation of scattering centers and features of the chemical state
of near-surface layers of materials. It is established using IR spectroscopy that treatment by Ar+ ion beam with a broad energy spectrum increases the reflection coefficient of the modified surface and additional resonance
lines related to the formation of oxides themselves and hydroxyl groups are revealed in the reflectance spectrum in the case
of formation of oxide film on the surface. 相似文献
7.
A. Milekhin M. Friedrich D.R.T. Zahn L. Sveshnikova S. Repinsky 《Applied Physics A: Materials Science & Processing》1999,69(1):97-100
Structures with CdS quantum dots produced by the Langmuir–Blodgett (LB) technique were investigated by Raman, IR, and UV spectroscopies.
The confinement effect of longitudinal optical (LO) phonons in CdS quantum dots was investigated by Raman spectroscopy. Surface
vibrational modes of CdS quantum dots were observed in IR spectra. It was shown experimentally that the frequency of the surface
vibrational modes depends on the properties of the surrounding media. An average size of CdS quantum dots of about 3–6.4 nm
was obtained from the analysis of UV measurements.
Received: 1 February 1999 / Accepted: 1 April 1999 / Published online: 19 May 1999 相似文献
8.
S.M. Huang Z. Sun Y.F. Lu M.H. Hong 《Applied Physics A: Materials Science & Processing》2002,74(4):519-523
Laser-induced removal of flash from heat sinks in integrated circuit (IC) packages has been studied. It is found that flash
can be effectively removed from heat sinks in plastic IC packages by laser deflashing. An optical microscope, an α-step surface
profiler and X-ray photoelectron spectroscopy are used to analyze the deflashing efficiency. Laser deflashing of IC packages
is based on laser ablation of flash materials. With an increase of laser fluence, the ablation rate increases. The laser fluence
is selected between the ablation threshold of flash materials and that of heat-sink materials. An acoustic wave is generated
by laser ablation of flash materials. Acoustic wave detection is used to monitor the surface cleanness during laser deflashing
and to determine the ablation threshold of flash materials.
Received: 18 April 2001 / Accepted: 14 September 2001 / Published online: 17 October 2001 相似文献
9.
Femtosecond ablation of ultrahard materials 总被引:4,自引:0,他引:4
G. Dumitru V. Romano H.P. Weber M. Sentis W. Marine 《Applied Physics A: Materials Science & Processing》2002,74(6):729-739
Several ultrahard materials and coatings of definite interest for tribological applications were tested with respect to their
response when irradiated with fs laser pulses. Results on cemented tungsten carbide and on titanium carbonitride are reported
for the first time and compared with outcomes of investigations on diamond and titanium nitride. The experiments were carried
out in air, in a regime of 5–8 J/cm2 fluences, using the beam of a commercial Ti:sapphire laser. The changes induced in the surface morphology were analysed with
a Nomarski optical microscope, and with SEM and AFM techniques. From the experimental data and from the calculated incident
energy density distributions, the damage and ablation threshold values were determined. As expected, the diamond showed the
highest threshold, while the cemented tungsten carbide exhibited typical values for metallic surfaces. The ablation rates
determined (under the above-mentioned experimental conditions) were in the range 0.1–0.2 μm per pulse for all the materials
investigated.
Received: 31 August 2001 / Accepted: 3 December 2001 / Published online: 20 March 2002 相似文献
10.
The surface chemical modification of polyurethane (PU) films was performed by an UV laser-induced chemical reaction in a polysaccharide
solution. This process may be applicable as hydrophilic packaging of implantable medical devices and in vivo sensors. When
a PU film in contact with an aqueous alginic acid (AAC) solution was irradiated with a XeCl laser, the PU film turned hydrophilic.
Contact angles of water on the film were reduced from 110° to 60°. Since light absorption of the AAC solution at 308 nm was
negligibly small, reactive sites were generated solely on the PU surface. There, AAC could be immobilized by chemical bonds
thus allowing for a nanometer-scaled grafting of this biomolecule. The mechanism was investigated by surface analyses with
Fourier-transform infrared spectroscopy (FT-IR), dye staining, ultraviolet-visible (UV-VIS) spectroscopy, and scanning electron
microscopy (SEM) techniques. A one-photon photochemical process could beidentified.
Received: 30 June 2000 / Accepted: 4 July 2000 / Published online: 13 September 2000 相似文献
11.
S. Gloor V. Romano W. Lüthy H.P. Weber V.V. Kononenko S.M. Pimenov V.I. Konov A.V. Khomich 《Applied Physics A: Materials Science & Processing》2000,70(5):547-550
Two-dimensional antireflective periodical microstructures for the IR range are fabricated on the surface of CVD diamond films.
These structures are created using an ArF excimer laser (λ=193 nm) and a direct writing scheme consisting of a beam collimator
and a microscope objective to focus the beam onto the sample. Two different arrays are investigated. One has a spacing of
3 μm and is produced with single shots and the other one has a spacing of 4 μm and is produced with three shots per spot.
The hole depth and shape are measured with an atomic force microscope (AFM). The optical transmittance and the scattering
properties of the structure at 10.6 μm are reported for a CO2 laser beam. With a spectrometer further transmission measurements in the range of 5 to 20 μm are performed.
Received: 16 September 1999 / Accepted: 11 October 1999 / Published online: 24 March 2000 相似文献
12.
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
13.
N. Esser 《Applied Physics A: Materials Science & Processing》1999,69(5):507-518
Only recently Raman spectroscopy (RS) has advanced into the study of surface phonons from clean and adsorbate-covered semiconductor
surfaces. RS allows the determination of eigenfrequencies as well as symmetry selection rules of surface phonons, by k-conservation limited to the Brillouin zone-center, and offers a significantly higher spectral resolution than standard surface
science techniques such as high-resolution electron energy loss spectroscopy. Moreover, surface electronic states become accessible
via electron–phonon coupling. In this article the fundamentals of Raman scattering from surface phonons are discussed and
its potential illustrated by considering two examples, namely Sb-monolayer-terminated and clean InP(110) surfaces. Both are
very well understood with respect to their atomic and electronic structure and thus may be regarded as model systems for heteroterminated
and clean semiconductor surfaces. In both cases, localized surface phonons as well as surface resonances are detected by Raman
spectroscopy. The experimental results are compared with surface modes predicted by theoretical calculations. On InP(110),
due to the high spectral resolution of Raman spectroscopy, several surface modes predicted by theory can be experimentally
verified. Surface electronic transitions are detected by changing the energy of the exciting laser light indicating resonances
in the RS cross section.
Received: 7 April 1999 / Accepted: 25 June 1999 / Published online: 16 September 1999 相似文献
14.
G. Fuhr C. Reichle T. Müller K. Kahlke K. Schütze M. Stuke 《Applied Physics A: Materials Science & Processing》1999,69(6):611-616
An electric cage-laser micro-turning lathe was realised and applied to contact-free handling and mechanical processing of
micro particles. Since particles with diameters of several micrometers cannot be fixed in mechanical chucks, an octode field
cage was used to trap and rotate a single particle in a fluid without any mechanical surface contact. A pulsed nitrogen laser
of high beam quality focused to about 1 μm in diameter could be adjusted independently of the cage position. The trapping
forces (negative dielectrophoresis) acting on a bead of 5 to 15 μm are up to several hundred pN. This and the surrounding
fluid damp down the effect of the laser pulses during bead processing. Examples demonstrating the possibilities of this technique
are shown. Microsystems with high optical quality were fabricated photolithographically or by laser direct-write chemical
vapor deposition (LCVD). Technical and biotechnological applications are discussed.
Received: 20 October 1999 / Accepted: 27 October 1999 / Published online: 10 November 1999 相似文献
15.
2 . Major peaks were assigned to direct fragments and recombination products ejected from the PS surface. The arrival profiles
of these ablation products varied from product to product and were fitted by using a shifted Maxwell–Boltzmann distribution
with a center-of-mass flight velocity [(1.4-5.6) ×105 cm/s] and a Knudsen layer temperature (350–3810 K). Two types of ablation products, whose velocities and temperatures showed
different dependences on laser fluence, were found to exist. Dynamical aspects in the decomposition of the polymer chain,
the ejection of various fragments, and their expansion are discussed on the basis of a photothermal ablation model, where
a heated surface layer with a temperature gradient along its depth plays an important role.
Received: 11 August 1998/Accepted: 12 August 1998 相似文献
16.
A. Yamada K.P. Ho T. Maruyama K. Akimoto 《Applied Physics A: Materials Science & Processing》1999,69(1):89-92
The feasibility of MoS2 layered compound as a substrate for GaN growth was investigated. GaN films were successfully grown on MoS2 by plasma-enhanced molecular beam epitaxy and the crystal quality of GaN on MoS2 was compared with that on Al2O3. For GaN grown on MoS2 substrate, it was found that the surface flatness observed by atomic force microscopy, stress in the film measured by Raman
spectroscopy, optical properties measured by photoluminescence spectroscopy, and threading dislocation density observed by
transmission electron microscopy show superior properties compared with that grown on Al2O3. These results suggest the layered compound such as MoS2, which has no dangling bonds on the surface and has lattice mismatching of 0.9% to GaN, has high potential for a substrate
of GaN growth.
Received: 1 March 1999 / Accepted: 8 March 1999 / Published online: 26 May 1999 相似文献
17.
F. Beinhorn J. Ihlemann K. Luther J. Troe 《Applied Physics A: Materials Science & Processing》1999,68(6):709-713
Micro-lenses with well-defined optical parameters are generated on polymethylmethacrylate (PMMA) substrates doped with diphenyltriazene
(DPT) by controlled use of a swelling effect generated under conditions of subablative excimer laser illumination. The surface
profiles depend on the laser spot size and energy density. A sensitively balanced combination of matrix softening, substrate
volume expansion due to photochemical nitrogen release, and surface tension is responsible for the final shape of the lenses.
Complete arrays of identical lenses with 15 μm diameters and a focal length of 30 μm are produced by irradiation of (0.25 wt. %)
DPT-PMMA with a single laser pulse at a wavelength of 308 nm and a fluence of 3 J/cm2. It is shown experimentally and theoretically that appropriate volume expansion is possible without introducing internal
light scattering due to the formation of small bubbles.
Received: 7 April 1999 / Accepted: 8 April 1999 / Published online: 5 May 1999 相似文献
18.
A. E. Chmel’ A. D. Semenov A. N. Smirnov V. S. Shashkin 《Physics of the Solid State》1999,41(6):938-941
A Raman spectroscopic investigation of the fractal structure on the surface of cracks of different size scales in glassy SiO2 is reported. A study was made of the crack surface and of the distorted layer formed after grinding and polishing and comminution.
The parameters of the fractal structure thus found reflect the properties of the material and the crack nature; namely, fractal
dimension is of greater importance for more compact materials, and the geometric size of fractal units (i.e., the size in
real space) correlates with crack dimensions.
Fiz. Tverd. Tela (St. Petersburg) 41, 1030–1034 (June 1999) 相似文献
19.
E. Cappelli C. Scilletta G. Mattei V. Valentini S. Orlando M. Servidori 《Applied Physics A: Materials Science & Processing》2008,93(3):751-758
The structure of thin films deposited by pulsed laser ablation (PLD) is strongly dependent on experimental conditions, like
laser wavelength and fluence, substrate temperature and pressure. Depending on these parameters we obtained various kinds
of carbon materials varying from dense, mainly tetrahedral amorphous carbon (ta-C), to less compact vertically oriented graphene
nano-particles.
Thin carbon films were grown by PLD on n-Si 〈100〉 substrates, at temperatures ranging from RT to 800°C, from a rotating graphite target operating in vacuum. The laser ablation of the graphite target was performed by a UV pulsed ArF excimer laser (λ=193 nm) and a pulsed Nd:YAG laser, operating in the near IR (λ=1064 nm).
The film structure and texturing, characterised by X-ray diffraction analysis, performed at grazing incidence (GI-XRD), and
the film density, evaluated by X-ray reflectivity measurements, are strongly affected both by laser wavelength and fluence
and by substrate temperature.
Micro-Raman and GI-XRD analysis established the progressive formation of aromatic clusters and cluster condensation into vertically
oriented nano-sized graphene structures as a direct function of increasing laser wavelength and deposition temperature. The
film density, negatively affected by substrate temperature and laser wavelength and fluence, in turn, results in a porous
bulk configuration and a high macroscopic surface roughness as shown by SEM characterisation. These structural property modifications
induce a relevant variation also on the emission properties of carbon nano-structures, as evidenced by field emission measurements.
This work is dedicated to our friend Giorgio who passed away 20th August. 相似文献
20.
聚四氟乙烯材料表面激光改性与刻蚀 总被引:1,自引:0,他引:1
利用波长为248 nm的准分子激光束在不同激光能量密度下照射聚四氟乙烯(PTFE)材料的表面,并用扫描电镜(SEM)、X射线光电子能谱(XPS)、拉曼(Raman)光谱等手段对激光处理前后样品的表面形貌、化学成分和结构进行测量和分析,进而对激光与聚四氟乙烯相互作用的机理进行了研究。实验结果表明,激光辐照使聚四氟乙烯表面产生去氟效应,导致表面碳化、分子链的交联以及含氧基团的产生,随着激光能量密度的增加,C=C双键逐渐形成。这些结构的变化可以导致表面硬度和粘结性增强。激光能量密度的大小对照射后样品表面的物理性质和化学结构有着重要的影响,它是聚合物表面激光改性和烧蚀的关键因素。 相似文献