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  • 1
    Electronic Resource
    Electronic Resource
    Mechanism of picosecond ultraviolet laser sputtering of sapphire at 266 nm (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 883-885 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultraviolet laser sputtering of sapphire was observed to result in droplet ejection when done in air, pressurized air, or in 20 mTorr pressure. Such droplets were collected and studied with scanning electron microscopy and optical microscopy. The collected particles were spherical and ranged in size up to 3 μm in diameter. Some particles appeared to have been molten and splattered on the collection plate. The size of the particles was independent of the ambient pressure. However, the collection efficiency of the collection plate was ∼30 times greater at 20 mTorr pressure as compared to one atmosphere. The similar result for measurements of the sputter depth under a range of background pressure indicates that the mechanism for the laser sputtering of sapphire at 266 nm with 30 ps pulses and a fluence near 10 J/cm2 is independent of the ambient pressure. Redeposition of debris onto the sputtered sample was significantly greater in one atmosphere pressure than in reduced pressure. These findings indicate that hydrodynamic sputtering is the most likely mechanism for the laser sputtering of sapphire at high sputter rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102617
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  • 2
    Electronic Resource
    Electronic Resource
    Excimer laser ablation of ferrites (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2072-2075 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser etching of ferrites was previously done by scanning a focused continuous-wave laser beam on a ferrite sample in a chemical environment. We study the phenomenon of photo-ablation of Ni-Zn or Mn-Zn ferrites by pulsed 248-nm KrF excimer laser irradiation. A transfer lens system is used to project a grating pattern of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluence for ablation at the ferrite surface is about 0.3 J/cm2. A typical fluence of 1 J/cm2 is used. The etched grooves produced are typically 20–50 μm wide, with depths achieved as deep as 70 μm . Groove straightness is good as long as a sharp image is projected onto the sample surface. The wall angle is steeper than 60 degrees. Scanning electron microscopy of the etched area shows a "glassy'' skin with extensive microcracks and solidified droplets being ejected that is frozen in action. We found that this skin can be entirely removed by ultrasonic cleaning. A fairly efficient etching rate of about 10 nm/pulse for a patterned area of about 2 mm×2 mm is obtained at a fluence of 1 J/cm2. This study shows that projection excimer laser ablation is useful for micromachining of ferrite ceramics, and indicates that a hydrodynamic sputtering mechanism involving droplet emission is a cause of material removal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348915
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Transient absorption and fluorescence spectroscopy in fused silica induced by pulsed KrF excimer laser irradiation (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3369-3371 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have carried out in situ transient absorption and fluorescence spectroscopy measurements in two "wet''(OH content ∼0.1%) fused silica samples (Suprasil II from Heraeus Amersil and P-30 from Shin-Etsu Quartz Product) during KrF laser irradiation. Both samples exhibit an absorption peak at 210 nm corresponding to the E' center. For Suprasil II, there is also a 265 nm absorption peak, and both peaks increase with the number of irradiated pulses showing little relaxation after the laser was turned off. The region irradiated with three million pulses at 400 mJ/cm2 fluence ten months ago has a residual absorption of about 10%/cm at 210 nm. On the other hand, the P-30 shows a rapid increase in the 210 nm absorption in both the unirradiated and previously irradiated regions during the initial irradiation and levels off after a few thousand pulses. There is no residual absorption at the spot irradiated for 63 million pulses ten months ago. However, the initial rate of increase in the previously irradiated spot is twice as high as compared to the unirradiated spot. This suggests the density of the precursor state for the E' center is higher in the previously irradiated region. The fluorescence intensity at 650 nm increases with the induced absorption for Suprasil II, but is almost independent of the number of irradiation pulses in P-30. The quasilinear repetition-rate dependence suggests the fluorescence is transient in nature and relaxes partially between successive laser pulses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105703
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  • 4
    Electronic Resource
    Electronic Resource
    Efficient pulsed laser removal of 0.2 μm sized particles from a solid surface (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2217-2219 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser cleaning with pulsed ultraviolet and infrared lasers is successfully employed to remove particulate contamination from silicon wafer surfaces and from delicate lithography membrane masks. Particulate material investigated include latex, alumina, silicon, and gold. Gold particles as small as 0.2 μm can be effectively removed. This new and highly efficient laser cleaning is achieved by choosing a pulsed laser with short pulse duration (without causing substrate damage), and a wavelength that is strongly absorbed by the surface; the removal efficiency is further enhanced by depositing a liquid film of thickness on the order of micron on the surface just before the pulsed laser irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104931
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  • 5
    Electronic Resource
    Electronic Resource
    Modulation of clonal progression in B16F1 melanoma cells (1991)
    Springer
    Clinical & experimental metastasis 9 (1991), S. 151-162 
    Details
    ISSN: 1573-7276
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have examined the effects of the microenvironment on the frequency and generation of metastatic variant cells in both parental B16F1 melanoma cells and nascent clones. The metastatic abilities of cultured B16F1 cells were tested after a period of growth in the presence or absence of a second cell population separated from each other by a transwell membrane (0.45μm pore size). The first population is defined as the ‘responder’ cells and the second as the ‘stimulator’ cells. We found that the presence of 105 B16F1 stimulator cells during the growth of responder B16F1 cells from ∼104 to ∼106 cells resulted in cells with an increased metastatic phenotype (〉 8-fold increase in median number of lung tumors relative to untreated B16F1 parental cells). The presence of stimulator cells also increased the metastatic phenotype of nascent clones, which were grown to a population size of 〈106 cells, suggesting that the rate of generation of metastatic variants of the responder B16F1 clones was affected by the stimulator cells. Other cell lines, including highly metastatic B16F10 and BL6 melanoma cells, and KHT35-L1 fibrosarcoma cells, were effective stimulator cells when as few as 104 cells were added to transwells. In addition, normal immortalized NIH 3T3 cells were effective stimulator cells only at 105 cells/transwell. The cell density at which untreated parental B16F1 cells were harvested (3×103−3 × 105 cells/cm2) did not affect the median number of lung tumors significantly. These results suggest that factors released from both tumor and immortalized normal cells can modulate epigenetic changes in the metastatic phenotype of B16F1 melanoma cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01756386
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  • 6
    Electronic Resource
    Electronic Resource
    Expression of a hepatitis E virus (HEV)-trpE fusion protein containing epitopes recognized by antibodies in sera from human cases and experimentally infected primates (1992)
    Springer
    Archives of virology 123 (1992), S. 335-349 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A 1700 base cDNA fragment coding for the putative structural gene(s) of hepatitis E virus (HEV) was inserted into the pATH 10 expression vector. The fusion protein (C2) expressed by this plasmid was found to contain epitopes recognized by anti-HEV antibodies. C 2 protein was used in a Western blot format to examine its usefulness in detecting anti-HEV antibodies in well documented human cases of HEV and non-human primates infected with HEV. Both IgM and IgG anti-HEV could be detected in our Western blot assay. This Western blot assay was found not to detect antibodies from acute-phase sera from patients with either HAV or HBV. The C 2 protein contains broadly cross-reactive epitopes, and the Western blot assay was able to detect anti-HEV antibodies in patient sera from Asia, Africa, and North America. The optimum serum dilution for the detection of both IgM and IgG was 1:25.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01317268
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Optical and acoustic study of nucleation and growth of bubbles at a liquid-solid interface induced by nanosecond-pulsed-laser heating (1994)
    Springer
    Applied physics 58 (1994), S. 407-415 
    Details
    ISSN: 1432-0630
    Keywords: 64.70.Fx ; 79.20.Ds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The dynamics of liquid-vapor phase-change in the nanosecond time-scale induced by pulsed-laser heating of a liquid on a solid sample is studied by means of optical reflectance and scattering measurements, and the piezoelectric detection technique. The liquids studied include water, ethanol, methanol, IsoproPropyl Alcohol (IPA), and mixtures of water and IPA. The threshold fluence for nucleation is determined with high accuracy using the optical and acoustic signals. Heat diffusion calculations performed for the threshold fluences indicate that the liquids are sufficiently superheated before nucleation sets on. The transient optical reflectance signal is analyzed by an effective-medium theory to provide bubble-growth kinetics, so that the bubble-growth velocity for the test liquids could be estimated. In addition, it is observed that, following the thermally induced nucleation, repetitive acoustic cavitation at the surface of the solid sample occurs, with a time interval related to the speed of sound in the liquid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323618
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  • 8
    Electronic Resource
    Electronic Resource
    Laser cleaning: Laser-induced removal of particles from surfaces (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 2 (1993), S. 63-70 
    Details
    ISSN: 1057-9257
    Keywords: Particulate ; Contamination ; Laser-induced removal ; Particle removal ; Laser cleaning ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Pulsed-laser-induced removal of particles from surfaces is a new cleaning technique. This laser cleaning can be performed on dry surfaces as well as on wet surfaces with a micron-thick liquid film during pulsed laser irradiation to provide enhanced removal efficiency. Using the latter technique, to be called ‘steam laser cleaning’ here, we are able to remove epoxy, alumina, silicon or gold particles with diameters in the range 0.1-10 μm from silicon and other surfaces.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860020108
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