Threshold Level Laser Ablation of Yba2Cu3Ox+6 at 351 nm, 248 nm, and 193 nm: Ejected Product Population and Kinetic Energy Distributions

1990 ◽  
Vol 191 ◽  
Author(s):  
L. Wiedeman ◽  
H. Helvajian
Keyword(s):  
Kinetic Energy ◽  
Laser Fluence ◽  
High Vacuum ◽  
Threshold Level ◽  
Product Formation ◽  
Laser Wavelength ◽  
Uv Laser ◽  
Desorption Process ◽  
Level Laser ◽  
193 Nm

ABSTRACTUsing a sintered Yba2Cu3Ox+6 wafer in high vacuum, we have measured the photo-ejected products and kinetic energies at selected UV laser wavelengths (351 nm, 248 nm, and 193 nm) where the laser fluence is maintained near product formation threshold. At these fluences, we are well below the above surface plasma formation threshold and do not detect; any evidence for surface melting. Our results show that, for a specific laser wavelength, both the ion and the neutral mass spectrum agree. The measured spectrum shows that the photablated products consist only of atomic and diatomic species. In addition, the oxygen is bound only to the yttrium and barium. Our measurements further show that, for a specific ejected species, the yield is dependent on both the laser fluence and wavelength. However, the measured KE distribution is independent of the laser fluence for fluences near threshold. The species are ejected with mean KE between 6–9 eV and no species has kinetic energy in excess of 13 eV Our results imply that for UV laser threshold fluence ablation, the excitation/desorption process is nonthermal.

UV Tunable Laser Ablation of YBa2Cu3Ox+6: Changes in the Product Population and Kinetic Energy Distributions as a Function of the Laser Wavelength and Target Bulk Temperature

1990 ◽  
Vol 191 ◽  
Author(s):  
L. Wiedeman ◽  
H. Helvajian
Keyword(s):  
Laser Ablation ◽  
Kinetic Energy ◽  
Optical Transition ◽  
Tunable Laser ◽  
Product Formation ◽  
Laser Wavelength ◽  
Bulk Temperature ◽  
Uv Laser ◽  
Laser Fluences ◽  
Population Distributions

ABSTRACTWe have conducted two separate experiments in the UV laser ablation of a sintered Yba2Cu3Ox+6wafer. We have measured the photoejected population distributions using selected UV laser wavelengths (4.01, 4.17 and 4.35 eV) near the 4.1 eV optical transition in Yba2Cu3Ox+6 In addition, we have measured the change in the ejected species kinetic energy as a function of the target bulk temperature. All the experiments were conducted at laser fluences well below the plasma formation threshold, and near that for product formation. Our results show that the UV laser ablation, at threshold fluences, proceeds via a nonthermal electronic excitation mechanism.

Excimer Laser Assisted Deposition of GaAs, AlAs, and [Al.Ga]as from Lewis Acid-Base Adducts

1986 ◽  
Vol 75 ◽  
Author(s):  
J. J. Zinck ◽  
P. D. Brewer ◽  
J. E. Jensen ◽  
G. L. Olson ◽  
L. W. Tutt
Keyword(s):  
Thin Films ◽  
Laser Beam ◽  
Substrate Temperature ◽  
Lewis Acid ◽  
Laser Fluence ◽  
Laser Wavelength ◽  
Acid Base ◽  
193 Nm ◽  
Source Materials ◽  
Reactive Gas

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.

Ejected Product Energy Distributions from Laser Ablated Solids

1988 ◽  
Vol 129 ◽  
Author(s):  
H. Helvajian ◽  
R. P. Welle
Keyword(s):  
Laser Ablation ◽  
Kinetic Energy ◽  
Product Formation ◽  
Uv Laser ◽  
Energy Distributions ◽  
Laser Threshold ◽  
Ion Kinetic Energy ◽  
The Mean ◽  
Mean Kinetic Energy ◽  
Kinetic Energy Distributions

ABSTRACTAt laser threshold fluences near ion product formation, we have measured the ejected ion kinetic-energy distributions from the UV laser ablation of crystalline aluminum and silver targets. The mean kinetic energy is found to be hyperthermal.

Pump-Probe Laser Photolytic Fragmentation Fluorescence Spectrometry of Isomeric Alkenes

1994 ◽  
Vol 48 (5) ◽  
pp. 616-619 ◽  
Author(s):  
Bobby J. Stanton ◽  
E. T. Monroe ◽  
E. L. Wehry
Keyword(s):  
Fluorescence Intensity ◽  
Laser Fluence ◽  
Laser Wavelength ◽  
Fluorescence Spectrometry ◽  
Probe Laser ◽  
Intermediate Species ◽  
Pump Probe ◽  
Laser Pump ◽  
Photolysis Laser ◽  
Spectral Patterns

The two-laser “pump-probe” photolytic fragmentation fluorescence spectrometry of three octenes and two nonenes is described. Probe-laser-induced C2 fluorescence (Deslandres-d'Azambuja system, C1II g→ A1II u) is detected. The relative C2 fluorescence intensity and spectral patterns exhibited by each alkene are strongly dependent on the probe-laser wavelength. The dependence of the fragment fluorescence intensity on the probe-laser fluence implies that the “probe” laser induces photofragmentation of intermediate species produced by the “photolysis” laser.

scholarly journals Pulsed UV Laser Processing of Carbosilane and Silazane Polymers

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 372 ◽  
Author(s):  
Samuel Ligon ◽  
Gurdial Blugan ◽  
Jakob Kuebler
Keyword(s):  
Laser Beam ◽  
Laser Processing ◽  
Scanning Speed ◽  
Inert Atmosphere ◽  
Laser Wavelength ◽  
Uv Laser ◽  
Glass Substrates ◽  
Polymer Precursors ◽  
Laser Systems ◽  
Pre Treatment

Freestanding SiCNO ceramic pieces with sub-mm features were produced by laser crosslinking of carbosilane and silazane polymer precursors followed by pyrolysis in inert atmosphere. Three different pulsed UV laser systems were investigated, and the influence of laser wavelength, operating power and scanning speed were all found to be important. Different photoinitiators were tested for the two lasers operating at 355 nm, while for the 266 nm laser, crosslinking occurred also without photoinitiator. Pre-treatment of glass substrates with fluorinated silanes was found to ease the release of green bodies during solvent development. Polymer crosslinking was observed with all three of the laser systems, as were bubbles, surface charring and in some cases ablation. By focusing the laser beam several millimeters above the surface of the resin, selective polymer crosslinking was observed exclusively.

Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength

1997 ◽  
Vol 51 (1) ◽  
pp. 87-91 ◽  
Author(s):  
W. F. Ho ◽  
C. W. Ng ◽  
N. H. Cheung
Keyword(s):  
Laser Pulse ◽  
Signal To Noise Ratio ◽  
Laser Wavelength ◽  
Spectrochemical Analysis ◽  
Liquid Jets ◽  
Single Shot ◽  
Transient Nature ◽  
Vapor Plume ◽  
193 Nm ◽  
532 Nm

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.

electromagnetic field at the particl e has to be computed numerically. An example of such a computation using a program based on [49] is given in Fig. 4. But not only doe s the Mie theory describe an enhancement of the laser intensity in the particles' near field, it also predicts that for certain values of the size parameter nd/X (d denoting the particle diameter, À the laser wavelength) the enhancement should be particularly efficient, resulting in a resonant intensity enhancement, the so-called "Mie-resonances". 3.2.2. Near-field induced substrate damage When inspecting contaminated samples by scanning electron microscopy (SEM) or atomic force microscopy (AFM ) after DLC using ns laser pulses, the consequences of the field enhancement process became obvious: all over the cleaned areas w e found substrate damages localized exactly at the former particle positions [35, 37-39]. These damages manifested as melting pools or even holes in the surface, typical examples can be seen in Fig. 5. The consequences for the laser cleaning process are obvious. The intensity enhancement reduces the maximum laser fluence that can be applied in the process. Usually in laser cleaning studies [19, 31 ] the laser fluence corresponding to the melting threshold of a bare surface is taken as the damage threshold fluence. Our experiments show clearly that this is an inadequate definition. Instead one must take into account the enhanced laser fluence underneath the particles, as it will be discussed in Section 4. Fro m the obtained AFM images we were able to analyse in detail the surface profile at the damaged sites. Here we found that for high field enhancement factors the silicon substrate was not only molten , but that some material was even ablated (see Sec. 4). The momentum transfer to the particles during the ablation process significantly contributes to the cleanin g process and hence local substrate ablation

2003 ◽  
pp. 327-330
Keyword(s):  
Laser Fluence ◽  
Near Field ◽  
Particle Diameter ◽  
Surface Profile ◽  
Field Enhancement ◽  
Damage Threshold ◽  
Laser Pulses ◽  
Laser Wavelength ◽  
Laser Cleaning ◽  
Intensity Enhancement

Investigations of Excimer Laser Effects on CVD Diamond Growth

1989 ◽  
Vol 162 ◽  
Author(s):  
Pehr E. Pehrsson ◽  
H. H. Nelson ◽  
F. G. Celii
Keyword(s):  
Gas Phase ◽  
Nucleation Site ◽  
Laser Wavelength ◽  
Diamond Growth ◽  
Uv Laser ◽  
Gas Phase Chemistry ◽  
Scanning Auger Microprobe ◽  
Novel Method ◽  
Size And Morphology ◽  
Phase Chemistry

ABSTRACTWe investigated UV laser irradiation as a method to modify the surface and gas phase chemistry in a diamond growth apparatus. In particular, attempts were made to reproduce reported laser-enhanced deposition. The variables included the laser wavelength and intensity, the precursor gas (and hence the gas-phase absorption), the flow rate, and the gas inlet orientation with respect to the filament. The samples were analyzed using optical microscopy, Scanning Electron Microscopy, the Scanning Auger Microprobe, and micro-Raman scattering. In all cases, the laser radiation suppressed or had no effect on diamond deposition in comparison to the adjacent unirradiated regions. The crystals that did grow in the irradiated regions were similar in size and morphology to those from the unirradiated areas, suggesting ablation or nucleation site blockage as possible deposition suppression mechanisms. The results suggest a novel method for diamond film patterning.

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
Keyword(s):  
Polymer Films ◽  
Laser Wavelength ◽  
Ablation Laser ◽  
193 Nm

scholarly journals CARS and Fluorescent study of ignition of H2/O2 mixtures upon photodissociation of O2 molecular

2018 ◽  
Vol 209 ◽  
pp. 00010
Author(s):  
Vitaly Kobtsev ◽  
Sergey Kostritsa ◽  
Dmitrii Kozlov ◽  
Alexey Pelevkin ◽  
Valery Smirnov ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Combustion Chamber ◽  
Test Bench ◽  
Combustion Process ◽  
Kinetic Mechanism ◽  
Uv Laser ◽  
Chain Reactions ◽  
Ignition And Combustion ◽  
193 Nm ◽  
Experimental Test Bench

The research is devoted to gas mixtures ignition by UV laser radiation. The dissociation of O2 molecules by a pulse of excimer ArF laser radiation at 193-nm wavelength with formation of the chemically active oxygen atoms initiating chain reactions which cause ignition of H2/O2 mixture was employed. The experimental test bench was created with CARS and fluorescent techniques for experimental investigation of some peculiarities of mixture ignition and combustion caused by such photo-dissociation, at conditions typical for combustion chamber. Two-dimensional numerical modeling of combustion process in model combustion chamber, based on kinetic mechanism of H2 oxidation including atom O(1P) and radicals OH(A2Σ+), was performed.

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