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1.
Damage mechanism and morphology characteristics of chromium film in femtosecond laser rear-side ablation 总被引:1,自引:0,他引:1
Wenjun Wang Xuesong Mei Kedian Wang Jinyou Shao Chengjuan Yang 《Applied Surface Science》2010,256(11):3612-3617
In this paper, damage mechanism and morphology characteristics of chromium film in femtosecond laser rear-side ablation are investigated. The film removing process includes two key sub-processes: the laser ablation dynamic process and subsequent breaking and ejecting dynamic process. Film morphology in rear-side ablation is determined by the interrelation between the laser energy and the film strength. When lower laser energy is used, residual out-layer film is relative thick and tends to break into some large fragments, which results in an irregular ablation shape. While when higher pulse energy is used, thinner residual film with weaker break strength breaks into small fragments, the ablation quality improves correspondingly. Besides laser energy and film property, energy distribution of laser beam also affects the ablation quality. In experiments, this kind of effect is researched by changing the focal position. It is found that ripples, which are familiar nano-structures in front-side ablation, also exist in rear-side ablation. These ripples are formed initially at the interface between quartz substrate and film, and their coverage varies with the energy distribution. Additionally, increasing number of scans is an effective method to shorten the period of ripples. 相似文献
2.
Wenjun Wang Xuesong Mei Gedong Jiang Kedian Wang Chengjuan Yang 《Optics & Laser Technology》2012,44(1):153-158
The microfabrication of films with femtosecond lasers has been researched widely for its high spatial resolution and sub-spot-size features. Compared with the common front-side ablation, femtosecond laser rear-side ablation mechanism of films is more complex due to the possible film breaking process. In this paper, the effect of film properties such as adhesion strength and cohesion strength on the material removing characteristics in femtosecond laser rear-side ablation of Cr film is investigated. The possible film breaking process in the rear-side ablation is analyzed firstly, and then some experiments with different films, the vapor deposited Cr film, the sputtered Cr film and the Cr film of photomask are performed. The experimental results indicate that the film properties are key factors influencing material removal characteristics for laser rear-side ablation. By varying film properties and laser fluence, femtosecond laser rear-side ablation technique can be applied in laser cleaning process and fabrication of nanostructures. The unique feature of rear-side ablation will widen the application of femtosecond laser micromachining technique. 相似文献
3.
S. I. Anisimov N. A. Inogamov Y. V. Petrov V. A. Khokhlov V. V. Zhakhovskii K. Nishihara M. B. Agranat S. I. Ashitkov P. S. Komarov 《Applied Physics A: Materials Science & Processing》2008,92(4):797-801
The mechanical action of laser exposure on a foil may result in the ablation of irradiated front layer and the rear-side spallation.
The dynamics of an Al foil is studied by means of two-temperature (2T) hydrodynamics and molecular dynamics (MD). It is found
that the rear-side spallation threshold F
s exceeds the front-side ablation threshold F
a. We propose to extend the common approach in laser-matter experiments by pump–probe measuring of the rear-side displacement. 相似文献
4.
ABSTRACT This paper presents a study of the effects of ablation direction, beam profile and outer environment on the width and morphology of micro-grooves ablated by a 10-ps, 532-nm laser with a changing range of fluences and scan speeds on 600?nm-thick CIGS (CuIn(1-x)Ga2Se x ) thin films. Experiments show that rear-side ablation by picosecond laser with a flat top beam in water environment yields a larger groove width than normal front-side ablation with a Gaussian beam in air, which is attributed to different material removal mechanisms, uniform energy distribution and the refraction of laser in water. The heat-affected zone and irregular edges induced by the tearing effect are the main defects of groove morphology associated with front- and rear-side ablation processes, respectively. Our studies indicate that flat top beam ablation, in general, inhibits the over-ablation in the central region, thereby improving the uniformity of grooves, though it does not eliminate the heat-affected zone and irregularity of two edges. The straightness of groove edges is further improved with the flat top beam ablation carried out in a water environment, resulting from the action of the shock wave in water. Hence, the nearly perfect micro-grooves can be fabricated with rear-side flat top beam ablation under water, which are characterized by steep sidewalls, straight edges and intact glass substrate without cracks. 相似文献
5.
P.D. Townsend R. Brooks D.E. Hole Z. Wu A. Turkler N. Can A. Suarez-Garcia J. Gonzalo 《Applied physics. B, Lasers and optics》2001,73(4):345-353
The presence of copper nanoparticles in alumina and silica modifies their luminescence, and the changes in spectra are influenced
by variations in the nanoparticle size distributions. Luminescence signals are sensitive to the total defect population. Thus
the luminescence not only reflects changes caused by thermal annealing, which can modify both intrinsic defects and the copper
nanoparticles, but also responds to the method of preparation of thin film layers. Copper nanoparticle influence on luminescence
is reported both for ion-implanted bulk silica and for copper in pulsed laser deposition within alumina. Luminescence thus
potentially offers a non-destructive monitor of the layer quality, reproducibility and growth conditions, as well as the state
and size of the copper nanoparticles.
Received: 29 June 2001 / Published online: 10 October 2001 相似文献
6.
A simple method for patterning of thin (15–650 nm) aluminum films on glass substrates by direct, low-power, laser-thermal
oxidation in water under common laboratory conditions is demonstrated. Local heating of the metal film enhances the formation
of aluminum oxide (hydrargillite, Al2O3–3H2O) and provokes breakdown of the passivation layer followed by local corrosion at temperatures close to the boiling point
of water. Moving the focus of an Ar-ion laser (λ=488 nm) over the aluminum film with a speed of several μm/s yields grooves
flanked by hydrargillite. Upon through oxidation of the metal these structures act as electrically insulating domains. Depending
on the film thickness, the minimum width of the line structures measures between 266 nm and 600 nm. The required laser irradiation
power ranges from 1.7 mW to 30 mW. It is found that the photo-thermal oxidation process allows for writing of two-dimensional
electrode patterns.
Received: 16 July 2001 / Accepted: 23 July 2001 / Published online: 2 October 2001 相似文献
7.
D. Voigt E.C. Schilder R.J.C. Spreeuw H.B. van Linden van den Heuvell 《Applied physics. B, Lasers and optics》2001,72(3):279-284
We have characterized a semiconductor amplifier laser system which provides up to 200 mW output after a single-mode optical
fiber at 780 nm wavelength. The system is based on a tapered semiconductor gain element, which amplifies the output of a narrow-linewidth
diode laser. Gain and saturation are discussed as a function of operating temperature and injection current. The spectral
properties of the amplifier are investigated with a grating spectrometer. Amplified spontaneous emission (ASE) causes a spectral
background with a width of 4 nm FWHM. The ASE background was suppressed to below our detection limit by a proper choice of
operating current and temperature and by sending the light through a single-mode optical fiber. The final ASE spectral density
was less than 0.1 nW/MHz, i.e. less than 0.2% of the optical power. Related to an optical transition linewidth of Γ/2π=6 MHz
for rubidium, this gives a background suppression of better than -82 dB. An indication of the beam quality is provided by
the fiber coupling efficiency of up to 59%. The application of the amplifier system as a laser source for atom-optical experiments
is discussed.
Received: 8 May 2000 / Revised version: 21 September 2000 / Published online: 7 February 2001 相似文献
8.
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10.
Spectroscopic measurements in the UV/VIS region show reduced transmission through laser-induced backside wet etching (LIBWE) of fused silica. Absorption coefficients of up to 105 cm−1 were calculated from the transmission measurements for a solid surface layer of about 50 nm. The temperatures near the interface caused by laser pulse absorption, which were analytically calculated using a new thermal model considering interface and liquid volume absorption, can reach 104 K at typical laser fluences. The high absorption coefficients and the extreme temperatures give evidence for an ablation-like process that is involved in the LIBWE process causing the etching of the modified near-surface region. The confinement of the ablation/etching process to the modified near-surface material region can account for the low etch rates observed in comparison to front-side ablation. 相似文献
11.
M. Lee S. Moon M. Hatano C.P. Grigoropoulos 《Applied Physics A: Materials Science & Processing》2001,73(3):317-322
A new double laser recrystallization technique that can produce ultra-large direction- and location-controlled lateral grains
is presented. An excimer laser is combined with a pulse-modulated Ar+ laser to yield grains of tens of micrometers in size. The effect of different parameters on lateral grain growth is investigated.
These parameters include the time delay between the two lasers, the excimer-laser fluence, the Ar+-laser power and the pulse duration. The process has a wide process window and is insensitive to both the excimer-laser fluence
and the Ar+-laser power fluctuations. Preheating of the a-Si film with the Ar+ laser before firing the excimer laser is necessary for inducing lateral grain growth. The transient excimer-laser irradiation
is believed to generate nucleation sites for initiating the subsequent lateral grain growth. The surface roughness of the
recrystallized poly-Si is measured by atomic force microscopy.
Received: 14 September 2000 / Accepted: 24 February 2001 / Published online: 27 June 2001 相似文献
12.
Y. Lin M.H. Hong W.J. Wang Y.Z. Law T.C. Chong 《Applied Physics A: Materials Science & Processing》2005,80(3):461-465
We report direct laser writing of lithography patterns with a feature width of 20±5 nm on thin photoresist film by combining a double-frequency femtosecond laser and a near-field scanning optical microscope. The obtained feature size is much smaller than the laser wavelength () and the aperture diameter (d) with a resolution of /20 and d/2, respectively. The lithography patterns were analyzed with an atomic force microscope and a scanning electron microscope. The effects of laser energy and writing speed on the feature size were investigated. The underlying physical mechanism was also discussed. PACS 07.79.Fc; 07.79.Lh; 42.70.Jk; 68.37.Hk; 81.16.Nd 相似文献
13.
We present a simple, easy, and straightforward spectroscopic approach for the determination of the wavelength of pulsed laser
systems with an accuracy of ≤0.006 cm-1 (180 MHz). This is better than currently realised by the best commercially available wavemeters for pulsed laser systems.
As an example, the temperature dependence of the emitted wavelength of a pulsed Nd:YAG laser has been studied in detail. Our
measurements indicate that the passively Q-switched monolithic nonplanar ring-oscillator Nd:YAG laser with a free spectral
range of the resonator of about 5.8 GHz can be tuned without mode hops over a range of 3.8 GHz. The concept is generally applicable
to any other wavelength regions of interest.
Received: 9 April 2001 / Revised version: 9 July 2001 / Published online: 19 September 2001 相似文献
14.
Visible femtosecond (fs) laser pulses have been obtained in a dye solution with a very simple traveling wave collinear configuration.
A femtosecond Ti:sapphire laser (790 nm) pumps the dye solution by two-photon absorption and simultaneously generates supercontinuum,
which seeds a light-amplification mechanism. Cross-correlation frequency-resolved optical gating measurements reveal a chirped
structure in the dye pulse. The shortest pulse duration achieved is 170 fs and the overall energy efficiency of the process
is typically 25%.
Received: 22 March 2001 / Revised version: 4 July 2001 / Published online: 19 September 2001 相似文献
15.
M.B. Danailov A.A. Demidovich A.N. Kuzmin O.V. Kuzmin V.L. Hait 《Applied physics. B, Lasers and optics》2001,73(7):671-676
Experimental results from studies of the laser characteristics of Nd:LSB crystals in both cw and passive Q-switching arrangements
are presented. The dependence of the main laser parameters on the output coupling and saturable absorber transmission for
two doping levels of Nd was investigated. It is demonstrated that due to its high absorption, low losses and intrinsic strong
thermal lensing, even at pump powers of less than 200 mW, the Nd:LSB has excellent properties in terms of efficiency, beam
quality and pulse duration. In addition, it exhibits high pulse-to-pulse and pulse width versus pump power stability.
Received: 11 June 2001 / Revised version: 30 July 2001 / Published online: 15 October 2001 相似文献
16.
Channels are traditionally machined in materials by drilling from the front side into the bulk. The processing rate can be
increased by two orders of magnitude for transparent materials by growing the channel from the rear side. The process is demonstrated
using nanosecond laser pulses to drill millimeter-sized channels through thick silica windows. Absorbing defects are introduced
onto the rear surface to initiate the coupling of energy into the material. Laser drilling then takes place when the fluence
exceeds a threshold. The drilling rate increases linearly with fluence above this threshold. While UV light drills about four
times faster than IR light, the pulse length (in the nanosecond regime) and the pulse repetition rate (in the 0.1–10 Hz range)
do not greatly influence the drilling rate per pulse.
Drilling rates in excess of 100 μm per pulse are achieved by taking advantage of the propagation characteristics of the plasma
created at the drilling front. The plasma during rear-side drilling generates a laser-supported detonation wave into the bulk
material. The geometry also seems to increase the efficiency of the laser-induced plasma combustion and shock wave during
the pulse by confining it in front of the channel tip.
Received: 1 July 1999 / Accepted: 17 April 2000 / Published online: 20 September 2000 相似文献
17.
Ion synthesis and laser annealing of Cu nanoparticles in Al2O3 总被引:1,自引:0,他引:1
A.L. Stepanov V.N. Popok D.E. Hole I.B. Khaibullin 《Applied Physics A: Materials Science & Processing》2002,74(3):441-446
Al2O3 samples with Cu nanoparticles, synthesised by ion implantation at 40 keV with a dose of 1×1017 ion/cm2 and a current density from 2.5 to 12.5 μA/cm2, were annealed using ten pulses from a KrF excimer laser with a single pulse fluence of 0.3 J/cm2. The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment
were studied by Rutherford backscattering (RBS), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM) and
optical spectroscopy. It was found that laser annealing leads to a reduction in the nanoparticle size without diffusion of
metal atoms into the bulk. The change in particle size and the possibility for oxidation of the copper particles are examined
in the framework of Mie theory. Calculations presented show that under excimer laser treatment, Cu nanoparticles are more
likely to be reduced in size than to undergo oxidation.
Received: 19 April 2001 / Accepted: 7 November 2001 / Published online: 23 January 2002 相似文献
18.
Pulsed solid-state laser system with fiber phase conjugation and 315 W average output power 总被引:2,自引:0,他引:2
Solid-state laser sources with high average output power and high beam quality are required for numerous applications in industry
and science. To improve the beam quality, stimulated Brillouin scattering (SBS) mirrors based on optical phase conjugation
are used to compensate for phase distortions in master oscillator power amplifier (MOPA) systems. SBS phase conjugation in
commercially available silica optical fibers facilitates the construction of high-power solid-state laser systems with high
beam quality. Here we present a flash lamp-pumped, passively Q-switched Nd:YAP system which delivers an average output power
of 315 W with M2=2.6 at a wavelength of 1.08 μm.
Received: 11 July 2001 / Revised version: 28 September 2001 / Published online: 23 November 2001 相似文献
19.
S. Düsterer H. Schwoerer W. Ziegler C. Ziener R. Sauerbrey 《Applied physics. B, Lasers and optics》2001,73(7):693-698
We optimize the conversion of laser energy into extreme ultraviolet (EUV) radiation by tailoring the laser parameters for
a laser-produced plasma generated from 20 μm diameter water droplets. It is shown that mass-limited targets require careful
adaption of laser-pulse energy and laser-pulse duration separately, rather than laser intensity, which seems to be adequate
for bulk targets. The optimal pulse duration scales with the droplet radius, and the optimal pulse energy with the droplet
volume. With optimized parameters, we obtain a conversion efficiency of 0.23% in 4π and 2.5% bandwidth for 13 nm radiation,
the future EUV lithography light.
Received: 16 July 2001 / Revised version: 25 September 2001 / Published online: 7 November 2001 相似文献
20.
A theoretical quantitative analysis of processing parameters for application of an elliptical laser beam to achieve maximum patterning area is the focus of this study. Direct laser patterning (DLP) of self-assembled monolayers (SAM) is achieved by localized heating of the sample above the SAM desorption temperature. Through use of elliptical laser beams in the present work, three goals are achieved by analyzing the heat diffusion model and related thermo-kinetics model: (1) optimal working conditions (combination of laser power, scanning velocity and aspect ratio) for DLP to produce maximum feature size, or highest processing velocity at a given power; (2) identification of conditions that reduces the potential thermal damage to the substrate; (3) shedding light on issues related to uniformity or homogeneity of heating a substrate using an elliptical laser beam. A heat diffusion model is employed to provide the resulting surface temperature caused by elliptical laser beams, and the coupled thermo-kinetics model is used to determine the final SAM coverage generated by DLP. Parametric analysis revealed that 70–150 mW can be used to pattern feature sizes in the range of 2–10 times of equivalent circular beam size. It is also found that each elliptical laser beam has a unique optimal aspect ratio to result in the widest feature size for a given laser power and scanning velocity. The edge transition width increases with an increase of the aspect ratio. Keeping the aspect ratio of elliptical laser beam small (i.e. β<20), a sharp edge definition could be obtained; if an aspect ratio larger than 30 is used, a surface with gradual edge definition could be obtained. 相似文献