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.

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.

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.

Threshold Fluence UV Laser Ablation of Single Crystal Bi2Sr2Ca1Cu2O8: Product Population and Kinetic Energy Distributions of Ejected Ionic Species

1990 ◽  
Vol 201 ◽  
Author(s):  
Lawrence Wiedeman ◽  
Hyun Sook Kim ◽  
Henry Helvajian
Keyword(s):  
Mass Spectrum ◽  
Kinetic Energy ◽  
Single Crystal ◽  
Mass Spectra ◽  
Laser Excitation ◽  
Population Distribution ◽  
Wavelength Dependence ◽  
Ionic Species ◽  
Uv Laser ◽  
Laser Fluences

AbstractWe have conducted an experiment which measures the product population and kinetic energy (KE) distributions from the UV laser induced decomposition of crystalline Bi2Sr2Ca1Cu2O8. We have measured these distributions at two laser wavelengths 248, 351. At a third wavelength (355 nm) we have measured the photoejected mass spectra from both a single crystal Bi2Sr2Ca1Cu2O8 sample and a polycrystalline Bi2Sr2Ca2Cu3O10 sample. For all the experiments, the laser fluence is maintained near the threshold for ion formation. The laser fluences are well below the level for instigating a laser induced above surface plasma. Our results show that the ejected products are not the consequence of a laser surface evaporation process. We measure a wavelength dependence in the ejected species population distribution and the ejected kinetic energy distribution (< KE > = 5 ± 1 eV.2eV FWHM) is indicative of an electronic excitation process. The measured ion mass spectra show atomic, diatomic (e.g. Sr2+), and oxide (e.g. SrO+, CaO+) species with lesser quantities of the complex oxides (e.g. S2O+). Distinctly absent from the mass spectra are the oxide compounds BiO+, CuO+, and the atomic species O+. Furthermore, the mass spectrum shows that at 248 nm laser excitation, the Bi+ species is the abundant photopro-duct. However, for both the 351 nm and 355 nm excitations, the Sr+ and SrO+ ions are measured as more abundant. Also, comparing the 355 nm laser excitation of the single and polycrystalline samples, there is very little difference in the photoejected species mass spectrum.

Photophysics of Polyatomic Species Ejection Following Uv Laser Ablation of Single Crystal Bi2Sr2Ca1Cu2O8

1991 ◽  
Vol 236 ◽  
Author(s):  
Lawrence Wiedeman ◽  
Hyun-Sook Kim ◽  
Henry Helvajian
Keyword(s):  
Laser Ablation ◽  
Gas Phase ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Film Material ◽  
Uv Laser ◽  
Surface Plasma ◽  
Laser Fluences ◽  
Series Of Experiments ◽  
Large Clusters

AbstractA series of experiments have been conducted which probe the origin of the polyatomic ions (e.g., Sr2O+, BiCu+) measured following the low fluence, pulsed UV laser irradiation of crystalline Bi2Sr2CaCu2O8 (BiSrCaCuO). The photoejection of polyatomic species presents a problem for the pulsed laser deposition (PLD) technique. The deposition of polyatomic products could limit epitaxial growth during thin film material processing. Our results indicate that the polyatomic species are not the consequence of a gas phase recombination, but are in fact directly produced. All experiments are done at laser fluences below that required for above surface plasma formation. As such, our results do not address the formation of large clusters within the dense plume in high fluence laser ablation.

Amorphous Diamond Films Deposited by Pulsed-Laser Ablation: the Optimum Carbon-Ion Kinetic Energy and Effects of Laser Wavelength

1998 ◽  
Vol 526 ◽  
Author(s):  
Douglas H. Lowndes ◽  
Vladimir I. Merkulov ◽  
A. A. Puretzky ◽  
D. B. Geohegan ◽  
G. E. Jellison ◽  
...  
Keyword(s):  
Optical Properties ◽  
Laser Ablation ◽  
Kinetic Energy ◽  
Energy Gap ◽  
Spot Size ◽  
Laser Wavelength ◽  
Film Deposition ◽  
Carbon Ions ◽  
Carbon Ion ◽  
Beam Focusing

AbstractA systematic study has been made of changes in the bonding and optical properties of hydrogen-free tetrahedral amorphous carbon (ta-C) films, as a function of the kinetic energy of the incident carbon ions measured under film-deposition conditions. Ion probe measurements of the carbon ion kinetic energies produced by ArF and KrF laser ablation of graphite are compared under identical beam-focusing conditions. Much higher C+ kinetic energies are produced by ArF-laser ablation than by KrF for any given fluence and spot size. Electron energy loss spectroscopy and scanning ellipsometry measurements of the sp3 bonding fraction, plasmon energy, and optical properties reveal a well-defined optimum kinetic energy of 90 eV to deposit ta-C films having the largest sp3 fraction and the widest optical (Tauc) energy gap (equivalent to minimum near-gap optical absorption). Tapping-mode atomic force microscope measurements show that films deposited at near-optimum kinetic energy are extremely smooth, with rms roughness of only ~ 1 Å over distances of several hundred nm, and are relatively free of particulates.

Photophysics of Polyatomic Species Ejection Following UV Laser Ablation of Single Crystal Bi2Sr2Ca1Cu2O8

1991 ◽  
Vol 235 ◽  
Author(s):  
Lawrence Wiedeman ◽  
Hyun-Sook Kim ◽  
Henry Helvajian
Keyword(s):  
Laser Ablation ◽  
Gas Phase ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Film Material ◽  
Uv Laser ◽  
Surface Plasma ◽  
Laser Fluences ◽  
Series Of Experiments ◽  
Large Clusters

ABSTRACTA series of experiments have been conducted which probe the origin of the polyatomic ions (e.g., Sr2O+, BiCu+) measured following the low fluence, pulsed UV laser irradiation of crystalline Bi2Sr2CaCu2O8 (BiSrCaCuO). The photoejection of polyatomic species presents a problem for the pulsed laser deposition (PLD) technique. The deposition of polyatomic products could limit epitaxial growth during thin film material processing. Our results indicate that the polyatomic species are not the consequence of a gas phase recombination, but are in fact directly produced. All experiments are done at laser fluences below that required for above surface plasma formation. As such, our results do not address the formation of large clusters within the dense plume in high fluence laser ablation.

scholarly journals Lithography and Etching‐Free Microfabrication of Silicon Carbide on Insulator Using Direct UV Laser Ablation

2020 ◽  
Vol 22 (4) ◽  
pp. 1901173
Author(s):  
Tuan‐Khoa Nguyen ◽  
Hoang-Phuong Phan ◽  
Karen M. Dowling ◽  
Ananth Saran Yalamarthy ◽  
Toan Dinh ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Laser Ablation ◽  
Uv Laser
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