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Glow discharge cleaning for surface contaminants removal from hydrodynamic gas bearing components, discussing equipment application to thin film lubricant vapor deposition
Particular features and the performance of two experimental systems are described for quantitative studies of thin-film nucleation and growth processes including epitaxial depositions. System I consists of a modified LEED-Auger instrument combined with high-resolution electron microscopy. System II is a UHV electron microscope adapted for in-situ deposition studies. The two systems complement each other ideally, and the combined use of both can result in a comprehensive investigation of vapor deposition processes not obtainable with any other known method.
Device design, fabrication, and operation of a linear charge coupled device (CCD) detector array integrated with a thin film optical waveguide and applications of this structure to integrated optical signal processing and fiber optical communications were discussed. A two phase, overlapping-gate CCD is connected in parallel by means of a series of gates to an array of photodiodes. The photodiode provides an electrode free surface region so that a highly efficient waveguide detector coupling technique can be implemented. A thermally-oxidized layer of SiO2 forms an effective substrate for the optical waveguide.
The preparation and radiometric properties of silicon detectors coated with fluorescent thin films are described. The films are deposited from solutions of clear plastics, such as acrylic resins, polyvinyl toluene or polystyrene, and of organic laser dyes in a common solvent. They are optically clear, mechanically and chemically stable, yet easily applied and removed. Multiple doped films of a few microns thickness exhibit broad-band absorption from less than 250 nm to about 450 nm and narrow band emissions with peaks ranging from 380 nm to 600 nm. Internal quantum efficiencies are close to 100 percent and fluorescence decay times are in the nanosecond range. When deposited on optically denser media, a large fraction of the fluorescent emission is trapped in the substrate. Silicon photodiodes coated with multiple doped films exhibit high external quantum efficiencies and virtually flat photon response in the near UV.
An analytic theory is presented for the width selection of Saffman-Taylor fingers in the presence of thin film effect. In the limit of small capillary number Ca and small gap to width ratio epsilon, such that epsilon much less than Ca much less than 1, it is found that fingers with relative width lambda less than 1/2 are possible such that lambda squared (1-lambda)/(1-2 lambda) = k epsilon/Ca(sup 3/2), where the positive constant k depends on the branch of solution and equals 2.776 for the first branch. A fully nonlinear analysis is necessary in this problem even to obtain the correct scaling law. It is also shown how in principle, the selection rule for arbitrary Ca can be obtained.
The optical response of single grain-boundary weak links in superconducting YBCO thin films has been investigated. At temperatures well below the transition temperature, the grain boundary exhibits an optical response which is qualitatively different from transition edge response. Using a resistively shunted-junction model for the grain-boundary weak link, we find that the optical response below the transition temperature can be described by radiation induced thermal modulation of the critical currents of the weak links. The dependence on the bias current and the temperature distinguishes the weak-link optical response from the transition edge optical response. We discuss novel aspects of a potential radiation detector based on grain-boundary weak-link junctions.
Method of measuring thickness of thin organic liquid film deposited in vacuum involves use of quartz-crystal monitor (QCM) calibrated by use of witness plate that has, in turn, calibrated by measurement of absorption of infrared light in deposited material. Present procedure somewhat tedious, but once calibration accomplished, thicknesses of organic liquid deposits monitored in real time and in situ by use of QCM.
The research group at CSU has conducted theoretical and experimental research on 'Ultra-Low-Cost Room Temperature SiC Thin Films.'
Presented is a total-Lagrangian displacement-based non-linear finite-element model of thin-film membranes for static and dynamic large-displacement analyses. The membrane theory fully accounts for geometric non-linearities. Fully non-linear static analysis followed by linear modal analysis is performed for an inflated circular cylindrical Kapton membrane tube under different pressures, and for a rectangular membrane under different tension loads at four comers. Finite element results show that shell modes dominate the dynamics of the inflated tube when the inflation pressure is low, and that vibration modes localized along four edges dominate the dynamics of the rectangular membrane. Numerical dynamic characteristics of the two membrane structures were experimentally verified using a Polytec PI PSV-200 scanning laser vibrometer and an EAGLE-500 8-camera motion analysis system.
Poly-silicon thin films on glass substrates are synthesized using laser initiated metal induced crystallization of hydrogenated amorphous silicon films. These films can be used to fabricate solar cells on low cost glass and flexible substrates. The process starts by depositing 200 nm amorphous silicon films on the glass substrates. Following this, 200 nm of sputtered aluminum films were deposited on top of the silicon layers. The samples are irradiated with an argon ion cw laser beam for annealing. Laser power densities ranging from 4 to 9 W/cm2 were used in the annealing process. Each area on the sample is irradiated for a different exposure time. Optical microscopy was used to examine any cracks in the films and loss of adhesion to the substrates. X-Ray diffraction patterns from the initial results indicated the crystallization in the films. Scanning electron microscopy shows dendritic growth. The composition analysis of the crystallized films was conducted using Energy Dispersive x-ray Spectroscopy. The results of poly-silicon films synthesis on space qualified flexible substrates such as Kapton are also presented.
Voice operated switching circuit for thin film personal communications and telemetry system
The present analytic theory for the width selection of Saffman-Taylor (1958) fingers in the presence of the thin film effect establishes that, in the limit of a small capillary number and a small gap-to-width ratio, fingers whose relative width is smaller than 1/2 are possible. It is established that a fully nonlinear analysis is required for this problem in order to obtain even the correct (and rather preliminary) scaling law. The way in which the selection rule for arbitrary small capillary number is obtainable is also presented.
We present a simple experimental scheme for estimating the cryogenic thermal transport properties of thin films using superconducting nanowires. In a parallel array of nanowires, the heat from one nanowire in the normal state changes the local temperature around adjacent nanowires, reducing their switching current. Calibration of this change in switching current as a function of bath temperature provides an estimate of the temperature as a function of displacement from the heater. This provides a method of determining the contribution of substrate heat transport to the cooling time of superconducting nanowire single photon detectors. Understanding this process is necessary for successful electrothermal modeling of superconducting nanowire systems.
Sputtering, slurry and doctor-blade techniques for depositing thin thermistor films of lanthanum- doped barium-strontium-titanate for bolometer application
The development is described of a laboratory model oxygen partial pressure sensor using a sputtered zinc oxide thin film. The film is operated at about 400 C through the use of a miniature silicon bar. Because of the unique resistance versus temperature relation of the silicon bar, control of the operational temperature is achieved by controlling the resistance. A circuit for accomplishing this is described. The response of sputtered zinc oxide films of various thicknesses to oxygen, nitrogen, argon, carbon dioxide, and water vapor caused a change in the film resistance. Over a large range, film conductance varied approximately as the square root of the oxygen partial pressure. The presence of water vapor in the gas stream caused a shift in the film conductance at a given oxygen partial pressure. A theoretical model is presented to explain the characteristic features of the zinc oxide response to oxygen.
The Marshall Space Flight Center is developing a thin film reflector for a Gamma Ray Imaging Telescope System (GRITS) using the Shuttle External Tank (ET). The concept is to install an inflatable reflector in the ET that could be transferred from the orbiter in orbit. This is a study of a scale model reflector for the ET GRITS application. The approach is to form 1/2 mil film into a spherical mirror mounted on a seven-foot diameter metal ring. The ring mount is sealed and slightly evacuated to pressurize the film into shape. Several different fabrication techniques were investigated using seamed gore designs to form the reflector. Also studied was casting a film into a seamless circular sheet. The goal for this model was to achieve a one milliradian (rms) surface curvature error over 90 percent of the reflector area. This curvature was measured by a laser scanning instrument. The results show how different reflector designs and fabrication techniques contribute to surface curvature and focusing errors.
The principle objectives of this ongoing research involve the preparation and characterization of polycrystalline single-domain thin films of BaTiO3 for photorefractive applications. These films must be continuous, free of cracks, and of high optical quality. The two methods proposed are sputtering and sol-gel related processing.
We are exploring the properties of electron-beam evaporated molybdenum thin films on silicon nitride coated silicon wafers at substrate temperatures between room temperature and 650 C. The temperature dependence of film stress, transition temperature, and electrical properties are presented. X-ray diffraction measurements are performed to gain information on molybdenum crystallite size and growth. Results show the dominant influence of the crystallite size on the intrinsic properties of our films. Wafer-scale uniformity, wafer yield, and optimal thermal bias regime for TES fabrication are discussed.