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Advanced Applications of Lasers in Materials Processing/Broadband Optical Networks/Smart Pixels/Optical MEMs and Their Applications. IEEE/LEOS 1996 Summer Topical Meetings:

Date 5-9 Aug. 1996

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Displaying Results 1 - 25 of 151
  • Digest IEEE/LEOS 1996 Summer Topical Meeting. Advanced Applications of Lasers in Materials and Processing [Table of Contents]

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    Freely Available from IEEE
  • Pulsed laser deposition of dielectric and superconducting materials: Mechanisms and applications

    Page(s): 3 - 4
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    The laser ablation method is suitable for the formation of metal oxide thin films, such as dielectric materials and high T/sub c/ superconductors. This is because the laser beam comes from outside the film formation chamber and therefore oxygen pressure can be chosen as a desired value for the growth of thin films. The author prepares PbTiO/sub 3/ thin films, SrTiO/sub 3/-BaTiO/sub 3/ dielectric strained superlattices, BaCaCuO superconducting thin films and AuBaCuO superconducting superlattices. View full abstract»

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  • Fabrication of silicon solar cells by laser processing

    Page(s): 7 - 8
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    We fabricated silicon solar cells using a laser processing technique. The goal here was to examine how laser processing can possibly be used for such an application. As the first attempt we tried to fabricate solar cells by the simplest method possible. Among a variety of laser processing techniques that are available for the present application, we chose pulsed laser deposition (PLD). Using PLD, we deposited thin n-Si layers on p-Si wafers, and successfully formed the p-n junction that is essential for the photovoltaic effect. View full abstract»

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  • Laser desorption of NO and CO from sodium nitrate and calcium carbonate crystals

    Page(s): 9 - 10
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    Pulsed laser irradiation of solid samples produces plumes of gaseous material suitable for mass or chemical analysis. The combination of laser desorption with various mass spectrometry techniques offers a method by which solid micro samples may be analyzed for elemental and chemical composition. Such techniques are being developed to characterize a variety of solid samples including soil, and hazardous mixed wastes. It is clear that the laser desorption analysis of mixed wastes involving molecular ionic compounds requires a detailed knowledge of the desorption properties of these components. Sodium nitrate (NaNO/sub 3/) and Calcium carbonate (CaCO/sub 3/) are of particular interest since each is a component in waste storage tanks at the Hanford nuclear reservation and a constituent of the earth's subsurface. In an attempt to develop laser desorption as an analysis tool, we have studied pulsed UV laser desorption from crystalline NaNO/sub 3/ and the calcite form of CaCO/sub 3/. View full abstract»

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  • Laser assisted deposition of mercury chalcogenides thin films in chemically reactive environment

    Page(s): 11 - 12
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    The results of an experimental study of major physico-technological considerations of thin film structure formation and elemental composition at laser vaporization and deposition of thin CdHgTe and MnHgTe films in a chemically reactive environment are presented. The laser vaporization and condensation took place in the mercury vapour (P=10/sup -1/-10/sup 3/ Torr). Presynthesized CdTe-Te(MnTe-Te) or Te plates were used as targets. A laser with /spl tau/=50-100 ns generation pulse duration, density of vaporization pulse power q=10/sup 8/-10/sup 9/ W/cm/sup 2/, was used for vaporization of the target material. View full abstract»

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  • Dynamics of pulsed laser ablation for thin film growth

    Page(s): 13 - 14
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    Fast imaging and sensitive spectroscopic investigations of laser ablation plume propagation reveal fundamental collisional phenomena relevant to film growth by pulsed laser deposition and optimized cluster growth via laser vaporization. Two phenomena will be described. The first involves the splitting of the ablation plume into distinct high and low energy components as a weak shock front forms during ablation into a low-density background gas. The second involves the dynamics of graphite ablation for vacuum deposition of tetrahedrally coordinated amorphous diamond films. View full abstract»

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  • Diagnostics of growth and film properties of amorphous silicon

    Page(s): 15 - 16
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    High quality amorphous hydrogenated silicon (a-Si:H) films were deposited by pulsed VUV F/sub 2/ laser CVD (157nm), allowing digital control of the deposition process. The photodeposition was performed in a parallel configuration with an average power of 4 W at a repetition rate of 50 Hz. The source gas was disilane. Nucleation and growth on native oxide-covered Si View full abstract»

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  • Acoustic wave monitoring in pulsed laser interaction with materials

    Page(s): 17 - 18
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    Audible acoustic waves generated during laser interaction with Al surface are studied, to monitor the interaction and to reflect the nature of interactions such as laser ablation and surface cleaning. The fast Fourier transform spectral analysis method was used to study the acoustic wave generation and to establish a relationship between the acoustic waves and laser ablation rate or cleaning efficiency. View full abstract»

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  • Photoluminescence and X-ray analysis of laser deposited II-VI thin films and multilayered structures

    Page(s): 19 - 20
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    This work aims to determine the best buffer layer for the deposition of II-VI heterostructures on silicon. The results obtained from laser ablated films (1 μm thick) of CdSe, CdS and CdTe at different substrate temperatures are presented. A Nd:YaG laser (λ=532 nm) was used to ablate and deposit II-VI compounds in a vacuum chamber pumped down to 10/sup -6/ Torr. X-ray spectra were analysed and grain dimensions were calculated accordingly to Debye Sherrer formula. Photoluminescence experiments were carried out to study radiative transition and emission efficiency of the laser ablated films. A detailed study of linewidth and spectral position of the exciton line versus temperature T was performed. Broad PL bands due to extrinsic luminescence are present both in CdS and CdSe films. This PL feature is related to impurity levels localized in the energy gaps of the films. Recombination of donor acceptor pairs occurs and they are studied as a function of T and laser power. View full abstract»

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  • Advanced laser processing of metals

    Page(s): 23 - 25
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    Summary form only given. The application of lasers span the entire commercial and industrial scene starting from the CD player at home to welding in automobile and aircraft plants. Processes such as welding and cutting of components in order of meters, drilling dimensions of mm to /spl mu/ms are widely accepted in manufacturing. Future applications in manufacturing include: nanometer size powder generation by laser ablation; Angstrom to micron size deposition by laser CVD; mm scale coating by laser cladding; surface modification and meter scale components by direct metal deposition. The laser is a tool which can provide energy density varying from 10/sup -3/ watts/cm/sup 2/ to 10/sup 12/ watts/cm/sup 2/. They have a wavelength range varying from UV (/sup a_/193 nm) to far infrared (10.6 /spl mu/m). Recently, high brightness lasers have created new opportunities for laser processing applications. This inertialess tool of optical energy has the potential to start a new era. The preferred approach for successful process development is to apply "atomic level understanding to applications". This paper discusses the science base for many of the important laser processing techniques. Emission, absorption and laser induced fluorescence spectroscopy have been applied for studying interaction physics whereas transport models are used for quantitative understanding of the effects of process parameters on the materials. Electron optical techniques are applied to characterize the processed materials and whenever possible an effort has been made to establish structure-property-process-parameters relationship. View full abstract»

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  • High speed ablation of glass using TEA-CO/sub 2/ laser

    Page(s): 26 - 27
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    Laser ablation has been applied to synthetic quartz and BK-7 glasses using the TEA-CO/sub 2/ laser for maskless high speed etching. The TEA-CO/sub 2/ laser beam with a 10.6 /spl mu/m wavelength and 80 ns pulse duration was focused by a ZnSe lens down to a spot diameter of about 400 /spl mu/m on the sample surface. The repetition-rates of laser were varied from 1 pps to 1000 pps to investigate the dependence of ablation rate on the repetition rate. The ablation was performed at atmospheric pressure and in a vacuum of 4.2 x 10/sup -5/ Torr. Ablated profiles including depth and width are observed by a surface profiler and optical microscopy. The chemical compositions of the ablated bottoms were measured by electron probe microanalysis. View full abstract»

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  • Excimer lasers as tools for material processing in manufacturing

    Page(s): 28 - 29
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    Since their initial demonstration 20 years ago, excimer lasers have developed from physicists' "toys" to powerful tools, offering unique benefits to a wide range of applications. Nearly all technical (plastics, ceramics, glasses, metals, semiconductors, composites) and biological/medical materials can be structured by the intense ultraviolet (UV) laser lights. Drilling of microholes for ink jet nozzle heads and for MCM microelectronic packaging, stripping of very tiny wires, annealing of TFT's for flat panel displays and high quality marking are well-known industrial introduced examples of this technique. Recently two very important breakthroughs were achieved. The first is in regard to the performance of the excimer laser itself. The second one is a much more advanced way of using UV photons more efficiently. View full abstract»

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  • Laser processing to improve residual surface stress of metal components

    Page(s): 30 - 31
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    Laser processing of water-immersed material has been developed to improve the residual surface stress of metal components. The process changes the stress field from tensile to compressive through irradiation by a frequency-doubled YAG laser or copper vapor laser (CVL). View full abstract»

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  • Terawatt lasers: probing unique material properties with novel diagnostic source

    Page(s): 32 - 33
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    Short pulse and high intensity lasers can produce bright ultrashort-pulse-duration X-rays, electrons and ions. They also make highly nonequilibrium plasmas that can be used to deposit thin films with unique material properties. We present new experimental results on all of these topics. We first report results on the characterization, control, and applications of ultrashort X-rays emitted from laser plasmas. It is demonstrated experimentally that the pulse duration may be controlled by adjusting the incident ultrashort-pulse laser flux. View full abstract»

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  • Pulsed laser deposition of doped epitaxial compound semiconductor films

    Page(s): 34 - 35
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    The past decade has seen rapid growth in fundamental studies of the pulsed laser ablation (PLA) process and its application for pulsed laser deposition (PLD). However, there has been relatively little use of PLD to grow doped, epitaxial compound semiconductor films. Nevertheless, it is clear that some of the advantages of the ablation process also should apply for exploratory semiconductor materials research, especially for complex multi-element materials. The authors consider this process for the growth of structurally high quality and highly doped epitaxial II-VI and I-III-VI materials. View full abstract»

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  • Multilayer multicomponent semiconductor structures for microelectronics formed using laser and thin film technology

    Page(s): 36 - 37
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    The authors present technological doping processes which enable one to obtain the smallest thicknesses of doped layers (300-500 nm). The use of a laser as a technological tool makes it possible to reduce the thickness of modified layers to 10 nm and to build a fully-automatic low-temperature technology for shallow p-n junctions and devices needed in the future. View full abstract»

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  • Advances in excimer laser surface processing of materials

    Page(s): 38 - 39
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    The use of pulsed excimer lasers to surface processing of materials hinges on an understanding of the nature of the interaction between the laser energy and the material. One of the advantages of excimer laser processing is the relative uniformity of that interaction across diverse materials. The short wavelength, (200-400 nm depending on the laser gas) and the short pulse length (30 ns) mean that for most materials, the energy is absorbed in a region of the surface that is shallow (10 nm) relative to the thermal diffusion length (100 nm) in the material. View full abstract»

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  • Applications of fs lasers to nonlinear spectroscopy and process control of Si

    Page(s): 43 - 44
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    Si(O0 1) interfaces are among the most technologically important for nonlinear optical analysis, yet their exceptionally weak interfacial second harmonic susceptibility )I12)hsa s strongly inhibited quantitative interface-specific second harmonic (SH) spectroscopy and related nonlinear optical process control applications. The advent of widely tunable. unamplified femtosecond (fs) solid-state lasers has overcome this banier by enabling unprecedented SH generation efficiency (- lo6 photons/s) with minimal interface heating. View full abstract»

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  • Application of ArF excimer laser in MOCVD growth and in situ characterisation of gallium nitride

    Page(s): 45 - 46
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    Laser-induced chemical vapour deposition (LCVD) is an attractive technology for the growth of films on fragile and thermally sensitive substrates at low temperature. The laser may simultaneously be used as a probe, both in excitation of semiconductors for in situ photoluminescence measurements and for spectroscopic analysis of MOCVD precursor dissociation paths. the authors describe application of an ArF excimer laser (193 nm, 6.4 eV) to growth and characterisation of gallium nitride. View full abstract»

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  • Diagnostics of laser-induced germanium growth by in situ spectroscopic ellipsometry

    Page(s): 47 - 48
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    Nucleation and growth of high quality amorphous hydrogenated germanium (a-Ge:H) films was initiated by ArF laser-induced CVD and monitored in situ by real time spectroscopic ellipsometry. The UV-laser power was varied between 3 W and 10 W. The depositions were carried out at low partial pressures of digermane from 0.05 /spl mu/bar to 6 /spl mu/bar, chamber pressures between 0.5 mbar and 12 mbar and substrate temperatures between 250/spl deg/C and 310/spl deg/C. The influence of the deposition parameters such as substrate temperature, laser power, digermane partial pressure and total pressure in the deposition chamber on the growth rate and the film properties was investigated in detail. Typical deposition rates were in the nanometer per minute range. View full abstract»

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  • Analysis of stearic acid adsorbed on silver surfaces using optical spectroscopic techniques

    Page(s): 49 - 50
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    This study involves the vibrational analysis of a lubricant/flake system which is routinely used in Ag-filled adhesives. The investigation focused on the interaction between the lubricant, in this case stearic acid, and a silver surface using temperatures that are employed in the curing of the polymer adhesive. The chemical nature of the stearic acid/Ag surface was probed with two vibrational spectroscopies: (1) surface enhanced Raman scattering (SERS), and (2) IR-visible sum-frequency generation (SFG). In addition to chemical specificity, numerous studies have shown that both techniques exhibit surface sensitivity to interfacial processes such as adsorption and decomposition. View full abstract»

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  • Digital etching of GaAs. The mechanism and the application

    Page(s): 51 - 52
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    In this paper, the phenomena of photo-assisted digital etching using a tunable DUV laser is introduced for gallium arsenide semiconductors and the mechanism of the digital etching is discussed. View full abstract»

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  • Tailoring of chemical, morphological, and mechanical surface properties of materials with laser radiation

    Page(s): 53 - 55
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    Following the requirements for present microsystems the necessary resolutions are restricted to about 100 /spl Aring/ in vertical direction and to higher than 10 /spl mu/m in lateral direction, respectively. The author shows that laser radiation has now found confirmed applications in the prototyping stages of device engineering and is now on the edge of also becoming a cornerstone technology in manufacturing of leading-edge devices. View full abstract»

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  • Tissue ablation as a function of laser pulsewidth

    Page(s): 56 - 57
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    The authors show that laser ablation of biological tissue shows pulsewidth dependence. At pulsewidths less than 10 picoseconds and with fluences near the breakdown threshold, tissue ablations are maximally precise and efficient, resulting in limited collateral tissue damage when compared to longer pulsewidth. View full abstract»

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  • Laser induced formation of adherent interfaces

    Page(s): 60a - 60b
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    In this paper the author reports a novel laser-based method to increase the adherence of coatings on high thermal expansion mismatched substrates. This method is based on on morphological modification of the substrate, which results in the creation of a three-dimensional thermal and composition graded interface. View full abstract»

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