Control of structures of deposited polymer films by ablation laser wavelength: Polyacrylonitrile at 308, 248, and 193 nm

1996 ◽  
Vol 79 (9) ◽  
pp. 7198-7204 ◽  
Author(s):  
Satoru Nishio ◽  
Tomonori Chiba ◽  
Akiyoshi Matsuzaki ◽  
Hiroyasu Sato
1997 ◽  
Vol 51 (1) ◽  
pp. 87-91 ◽  
Author(s):  
W. F. Ho ◽  
C. W. Ng ◽  
N. H. Cheung

The plasma plume emissions produced by pulsed (∼ 10 ns) laser ablation of liquid jets were monitored for spectrochemical analysis. Laser wavelengths at 532 and 193 nm were used, and sodium was the test analyte. As expected, the 532-nm laser pulse produced very intense plasma continuum emissions that masked the sodium signal for the first hundred nanoseconds, especially near the bright core of the vapor plume. Neither time-gating nor spatial masking could significantly improve the single-shot signal-to-noise ratio, since the transient nature of the emissions placed stringent demands on timing precision while the small size of the plume required accurate mask positioning—both antithetical to the inherent instability of jet ablation. In sharp contrast, the 193-nm laser pulse produced relatively dim plasma flash but intense sodium emissions, rendering it ideal for analytical applications.


2012 ◽  
Vol 111 (5) ◽  
pp. 053301 ◽  
Author(s):  
Qianli Ma ◽  
Vincent Motto-Ros ◽  
Fabrice Laye ◽  
Jin Yu ◽  
Wenqi Lei ◽  
...  

1995 ◽  
Vol 397 ◽  
Author(s):  
W. Marine ◽  
I. Movtchan ◽  
A. Simakine ◽  
L. Patrone ◽  
R. Dreyfus ◽  
...  

ABSTRACTReactive laser ablation of Si targets by ArF* excimer laser (wavelength 193 nm, pulse width 15 ns (FWHM)) was performed in He, Ar or O2 0.05-1 Torr atmospheres and led to Si-SiOx nanocluster thin film formation within laser-induced plasma plume. Optical spectroscopy and optical Time-of-Flight (TOF) measurements were carried out during ablation-deposition experiments. A number of large weak emission bands in blue and green-yellow spectral branches were observed both in inert gases and in oxygen ambient atmospheres and attributed to the emission from excited nanoparticles in the plasma plume. TOF measurements proved a different spatio-temporal evolution of this emission compare to the emission of monoatomic particles. The films exhibit photoluminescence bands in the UV region (around 290 nm and between 310-370 nm), in the blue (between 420 and 500 nm), and in the green-yellow (at 520-560 nm). The relative intensities of the luminescence bands depend on the average cluster size, which is determined by preparation conditions (nature and pressure of the ambient gas, laser fluence).


2009 ◽  
Vol 15 (2) ◽  
pp. 305-314 ◽  
Author(s):  
Chau-Wen Chou ◽  
Randall W. Nelson ◽  
Peter Williams

Drift measurements of initial ejection velocities of matrix-assisted laser desorption/ionization matrix compounds have been made as a function of ablating laser wavelength and laser fluence. For pulsed laser irradiation just above the matrix ion appearance threshold, initial ejection velocities of protonated molecular ions of an anthranilic acid target increase from ∼ 1350 m/s to ∼ 1640 m/s (kinetic energies of 1.3 eV and 1.9 eV, respectively) when the ablation laser wavelength is changed from 355 nm to 266 nm. Increasing the laser fluence per pulse by up to a factor of 10 above threshold results in the appearance of a slower component of the ejected ion flux. The results are interpreted by a photomechanical ejection model in which a photoexcited surface molecule instantaneously becomes larger and recoils away from the surface.


1997 ◽  
Vol 51 (7) ◽  
pp. 976-983 ◽  
Author(s):  
C. W. Ng ◽  
W. F. Ho ◽  
N. H. Cheung

We spectroscopically determined the temperature and electron density of the plasma plumes produced by pulsed-laser ablation of aqueous solutions containing sodium, lithium, and rubidium. With the use of a Nd:YAG laser at 532 nm and fluence of 3 J/cm2, the plasma produced was hot (low eV range) and extensively ionized, with electron density in the 1018 cm−3 range. Analyte line signals were initially masked by intense plasma continuum emissions and would only emerge briefly above the background when the plume temperature dropped below 1 eV during the course of its very rapid cooling. Since ionization was thermally induced, the intense plasma flash was inevitable. In contrast, 193-nm laser ablation at similar fluence generated plasmas of much lower (<1 eV) temperature but comparable electron density. Plasma continuum emissions were relatively weak, and the signal-to-background ratio was a thousand times better. Consequently, this “cold” plasma was ideal for sampling biologically important elements such as sodium, potassium, and calcium.


2005 ◽  
Vol 59 (12) ◽  
pp. 1427-1444 ◽  
Author(s):  
Danielle Cleveland ◽  
Peter Stchur ◽  
Xiandeng Hou ◽  
Karl X. Yang ◽  
Jack Zhou ◽  
...  

It has been shown that an increase in sensitivity and selectivity of detection of an analyte can be achieved by tuning the ablation laser wavelength to match that of a resonant gas-phase transition of that analyte. This has been termed resonant laser ablation (RLA). For a pulsed tunable nanosecond laser, the data presented here illustrate the resonant enhancement effect in pure copper and aluminum samples, chromium oxide thin films, and for trace molybdenum in stainless steel samples, and indicate two main characteristics of the RLA phenomenon. The first is that there is an increase in the number of atoms ablated from the surface. The second is that the bandwidth of the wavelength dependence of the ablation is on the order of 1 nm. The effect was found to be virtually identical whether the atoms were detected by use of a microwave-induced plasma with atomic emission detection, by an inductively coupled plasma with mass spectrometric detection, or by observation of the number of laser pulses required to penetrate through thin films. The data indicate that a distinct ablation laser wavelength dependence exists, probably initiated via resonant radiation trapping, and accompanied by collisional broadening. Desorption contributions through radiation trapping are substantiated by changes in crater morphology as a function of wavelength and by the relatively broad linewidth of the ablation laser wavelength scans, compared to gas-phase excitation spectra. Also, other experiments with thin films demonstrate the existence of a distinct laser–material interaction and suggest that a combination of desorption induced by electronic transition (DIET) with resonant radiation trapping could assist in the enhancement of desorption yields. These results were obtained by a detailed inspection of the effect of the wavelength of the ablation laser over a narrow range of energy densities that lie between the threshold of laser-induced desorption of species and the usual analytical ablation regime. Normal ablation employs high-power lasers in an attempt to create a vapor plume without selective vaporization, and with a stoichiometry that accurately represents the stoichiometry of species in the solid sample. RLA, as a method of selective vaporization, appears to provide an opportunity to exploit selective vaporization in new ways.


1992 ◽  
Vol 285 ◽  
Author(s):  
A.J. Pedraza ◽  
J.-Y. Zhang ◽  
H. Esrom

ABSTRACTA new technique for selective metallization of aluminum nitride (AIN) has been previously reported (1). It involves the use of an excimer laser to activate the AIN surface followed by electroless plating (Cu,Ni,Au) of the irradiated areas. The mechanism of decomposition of ALN is accompanied by ablation and the formation of an Al film on the substrate surface. Ablation rates are reported here as a function of fluence and number of pulses for three different wavelengths λ = 193 nm (ArF), λ = 248 (KrF) and λ = 351 nm (XeF).The effect of laser wavelength on the ablation rate is discussed. The ablation rates for Al were zlso measured and are compared with the AIN ablation rates. A numerical thermal model is used to analyze the mechanisms of laser ablation of both materials. The evaporation kinetics are incorporated into the model. The Clausius-Clapeyron approximation is used to make a self-consistent calculation of boiling and decomposition temperatures.


1986 ◽  
Vol 75 ◽  
Author(s):  
J. J. Zinck ◽  
P. D. Brewer ◽  
J. E. Jensen ◽  
G. L. Olson ◽  
L. W. Tutt

AbstractLaser-assisted deposition of GaAs, AlAs and [AIGa]As thin films on Ge(100) substrates from trimethylgallium-trimethylarsenic and trimethylaluminumtrimethylarsenic Lewis acid-base adduct source materials is reported. A parametric study has been performed in which reactive gas pressure, substrate temperature, laser fluence, laser wavelength (248 nm or 193 nm). and orientation of the laser beam with respect to the substrate have been varied. In the case of irradiation parallel to the substrate, stoichiometric films of GaAs and [AIGa]As have been obtained. The data suggest that for irradiation perpendicular to the substrate a competition exists between desorption and photodeposition, which adversely affects film stoichiometry under the conditions studied.


2011 ◽  
Vol 115 (12) ◽  
pp. 5049-5057 ◽  
Author(s):  
Seyedeh Zahra Mortazavi ◽  
Parviz Parvin ◽  
Ali Reyhani ◽  
Ahmad Nozad Golikand ◽  
Soghra Mirershadi

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