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  • 1
    Electronic Resource
    Electronic Resource
    Laser-target interactions during pulsed laser deposition of superconducting thin films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5433-5439 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The theoretical analysis of thermal effects induced by nanosecond laser irradiation on bulk YBa2Cu3O7 superconductor targets provides insight into the nature of the target's ablation/evaporation characteristics during pulsed laser deposition of superconducting thin films. We have simulated the thermal history of YBa2Cu3O7 targets under intense nanosecond laser irradiation by numerically solving the one dimensional heat flow equation and taking into account the phase changes occurring at the near surface of the target. The numerical method is based on a higher-order finite difference scheme with a smaller truncation error and is not restricted by any stability criterion, thereby allowing faster convergence to the exact solution. Temperature-dependent optical and thermal properties of the irradiated material as well as the temporal variation in the laser intensity can be taken into account by this method. During planar surface evaporation of the target material, the subsurface temperatures were calculated to be higher than the surface temperatures as a result of combination of two unique effects. While the evaporating surface of the target is constantly being cooled due to the latent heat of vaporization, subsurface superheating occurs due to the finite absorption depth of the laser beam. The effects of various laser and target parameters, including pulse energy density, pulse duration, absorption coefficient, thermal conductivity, and latent heat on the transient thermal characteristics of the irradiated target, have been investigated in detail. Subsurface superheating was found to increase with decreasing absorption coefficient and thermal conductivity of the target, and with increasing energy density. The superheating may lead to subsurface nucleation and growth of the gaseous phase which expands rapidly leading to microexplosions and "volume expulsion'' of material from the target.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350201
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  • 2
    Electronic Resource
    Electronic Resource
    Infrared absorption in n-type ZnSe/GaAs heteroepitaxial films (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2458-2460 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the variation of the absorption coefficient αf with wave number W, for Cl-doped n-type (9.4×1016–8×1018 cm−3) ZnSe epitaxial films grown on GaAs. Below the classical mid-infrared range of W, αf has large values (1.6×103–2.11×104 cm−1) appropriate for thin-film measurements, with αf proportional to W−p. Large variations of αf and p occur as a function of the free-electron concentration. The results are compared to a recent theoretical model by Ruda [J. Appl. Phys. 61, 3035 (1987)], which is specific to ZnSe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103850
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  • 3
    Electronic Resource
    Electronic Resource
    Luminescence of pulsed laser deposited Eu doped yttrium oxide films (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 404-406 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Europium doped yttrium oxide (Eu:Y2O3) phosphor thin films were grown using a pulsed laser deposition (PLD) technique at varying growth conditions. The structural characterization carried out on a series of Eu:Y2O3 films grown on (100) silicon at substrate temperatures in the range of 250–600 °C and oxygen pressure in the range of 10−5 Torr to 200 mTorr indicated that films were preferentially (111) oriented. Measurements of photoluminescence and cathodoluminescence properties of laser deposited Eu:Y2O3 thin films and powder used for laser target showed that the best in situ grown films were ∼10%–22% as bright as Eu:Y2O3 powder. A postdeposition annealing treatment of Eu:Y2O3 films led to further improvements in their brightness (up to ∼70% with respect to Eu:Y2O3 powder), with cluster sizes of 〈400 nm. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119551
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of residual gas pressures on the degradation of ZnS powder phosphors (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 4578-4583 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phosphor powder of ZnS:Cu,Al,Au has been subjected to electron bombardment (2 keV, 2 mA/cm2) in residual gas pressures ranging from 0.6×10−8 to 7.0×10−8 Torr. Auger electron spectroscopy and cathodoluminescence (CL), both excited by the same electron beam, were used to monitor changes in the surface chemistry and cathodoluminescent brightness versus vacuum conditions during electron bombardment. A direct correlation between the surface reactions and the degradation of CL brightness was observed. The formation of a nonluminescent ZnO layer on the surface of the phosphor was largely responsible for the degradation of the ZnS. The aging of the phosphor was not only a function of the charge per unit area (Coulomb dose) bombarding the surface, but also a function of residual gas pressure and composition. In particular, H2O had the greatest effect on the rate of degradation. The results are interpreted in terms of an electron-beam stimulated surface chemical reaction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367240
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  • 5
    Electronic Resource
    Electronic Resource
    Optical investigations of ion implant damage in silicon (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2591-2594 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion implantation damage in silicon has been studied utilizing a new optical technique (differential reflectometry). It has been demonstrated that differential reflectometry can be used to identify whether an implanted layer is crystalline, damaged crystalline, or amorphous. The intensity of interband transitions can be used to determine the thickness of a damaged crystalline layer over a submerged amorphous layer. Interference effects were utilized to determine the thickness of an amorphous layer. Thus, differential optical reflectance has far-reaching potential for characterizing implanted substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340996
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  • 6
    Electronic Resource
    Electronic Resource
    Low-pressure, low-temperature, and remote-plasma deposition of diamond thin films from water-methanol mixtures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2863-2865 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have deposited diamond thin films remote from the active plasma region using an electron cyclotron resonance chemical vapor deposition technique. Diamond films were fabricated at temperatures in the range of 550–650 °C and gas pressures between 25 and 60 mTorr. The volume ratio of water to methanol was varied from 1:20 to 1:5 to optimize diamond film growth. High methanol content resulted in multiple nucleation in the growing diamond film, while higher water content led to complete etching of the film. A positive electrical bias was found to be essential for diamond thin film growth remote from the plasma region. The films were characterized by x-ray diffraction, micro-Raman, and scanning electron microscopy for phase identification, surface morphology, and bonding characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108058
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  • 7
    Electronic Resource
    Electronic Resource
    Luminescence behavior of pulsed laser deposited Eu:Y2O3 thin film phosphors on sapphire substrates (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3058-3060 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Europium-doped yttrium oxide (Eu:Y2O3) luminescent thin films have been grown in situ on single crystal (0001) sapphire substrates using a pulsed laser deposition technique. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. The photoluminescence (PL) and cathodoluminescence (CL) brightness data obtained from the Eu:Y2O3 films grown under optimized conditions have indicated that sapphire is a promising substrate for the growth of high quality Eu:Y2O3 thin film red phosphor. The success in the fabrication of Eu:Y2O3 films with high PL and CL brightness is attributed to favorable optical properties (low absorption of and low refractive index for red light) of the substrate material and improved growth of grains with unidirectional orientation on (0001) sapphire substrates. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122671
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  • 8
    Electronic Resource
    Electronic Resource
    Significant reduction of cathodoluminescent degradation in sulfide-based phosphors (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1838-1839 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The degradation of cathodoluminescent (CL) brightness under prolonged electron-beam excitation of phosphors has been identified as one of the outstanding critical issues for flat-panel field-emission displays. In this letter, we have demonstrated that a TaSi2 coating on Y2O2S:Eu3+ phosphors substantially inhibits the cathodoluminescent degradation characteristics without reducing its efficiency. The coating was deposited by pulsed laser deposition of TaSi2 targets onto a fluidized bed containing phosphor particles. Cathodoluminescent degradation experiments conducted at 2 keV and at 150 μA/cm2, showed that the CL brightness decreased by more than 50% after a Coulomb load of 15 C/cm2 on the uncoated material. In contrast, the TaSi2-coated phosphor powders showed much less degradation, with CL brightness only decreasing by approximately 12% after electron irradiation with the same dose. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121195
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  • 9
    Electronic Resource
    Electronic Resource
    Improved luminescence properties of pulsed laser deposited Eu:Y2O3thin films on diamond coated silicon substrates (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3335-3337 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Europium activated yttrium oxide (Eu:Y2O3) phosphor films have been grown in situ on (100) bare and diamond-coated silicon substrates using a pulsed laser deposition technique. Diamond-coated silicon substrates were prepared using hot filament chemical vapor deposition of diamond onto silicon. Photoluminescence brightness from Eu:Y2O3 films grown at 700 °C on diamond-coated silicon substrates was about twice that of films on bare silicon, and reached 80% of the brightness of powders. The higher brightness from Eu:Y2O3 film on diamond-coated silicon substrates is attributed to reduced internal reflections from the Eu:Y2O3 film surface, which results from the roughness of the diamond layer. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120329
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  • 10
    Electronic Resource
    Electronic Resource
    Ge concentration in regrown GaAs for ohmic contacts (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3835-3837 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dissociation and solid phase epitaxial regrowth of GaAs in Ti/Ge/Ni/GaAs were investigated using the transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) of x-rays with spatial resolution approaching 2 nm. A ternary Ni2.4GaAs phase, ∼130 nm thick, was formed by 300 °C in situ anneals of 65 nm Ni film on GaAs. After this in situ anneal, films of 30 nm Ge and 20 nm Ti were deposited in sequence. The EDS analysis showed that Ni2.4GaAs transformed into Ni–As and Ni–Ga binaries after annealing at 500 °C for 5 min, while ∼30 nm of GaAs regrew by solid phase epitaxial regrowth from decomposition of the binary phases. High spatial resolution microanalysis allowed detection of ∼1×1020 cm−3 Ge in the regrown GaAs. This confirms that Ge is incorporated into GaAs during regrowth for ohmic contact formation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120519
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