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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Nonlinear optical processing with Fabry-Perot interferometers containing phase recording media

New techniques in nonlinear optical processing are explored, based on the operation of intensity level selection as performed by a Fabry-Perot interferometer containing a phase object. The image being processed is recorded on a medium between the mirrors as a spatially varying phase shift less than pi. The interferometer only transmits light through those portions of the object that corresponds to a single value of the phase and hence to a single intensity level in the input. More complicated operations such as thresholding and analog-to-digital conversion are performed by modulating the light source as the different levels are selected. Photoresist and lithium niobate have been used as phase objects, and experimental data for both are presented. Three kinds of Fabry-Perot interferometers have been used to demonstrate nonlinear processing using coherent and incoherent light. Color images have been produced with black and white inputs and white light illumination.

Bartholomew, B. J.↗
NASA NTRS1979

Semiconductor technology program. Progress briefs

The current status of NBS work on measurement technology for semiconductor materials, process control, and devices is reported. Results of both in-house and contract research are covered. Highlighted activities include modeling of diffusion processes, analysis of model spreading resistance data, and studies of resonance ionization spectroscopy, resistivity-dopant density relationships in p-type silicon, deep level measurements, photoresist sensitometry, random fault measurements, power MOSFET thermal characteristics, power transistor switching characteristics, and gross leak testing. New and selected on-going projects are described. Compilations of recent publications and publications in press are included.

Bullis, W. M.↗
NASA NTRS1980

Solar cells and modules from dentritic web silicon

Some of the noteworthy features of the processes developed in the fabrication of solar cell modules are the handling of long lengths of web, the use of cost effective dip coating of photoresist and antireflection coatings, selective electroplating of the grid pattern and ultrasonic bonding of the cell interconnect. Data on the cells is obtained by means of dark I-V analysis and deep level transient spectroscopy. A histogram of over 100 dentritic web solar cells fabricated in a number of runs using different web crystals shows an average efficiency of over 13%, with some efficiencies running above 15%. Lower cell efficiency is generally associated with low minority carrier time due to recombination centers sometimes present in the bulk silicon. A cost analysis of the process sequence using a 25 MW production line indicates a selling price of $0.75/peak watt in 1986. It is concluded that the efficiency of dentritic web cells approaches that of float zone silicon cells, reduced somewhat by the lower bulk lifetime of the former.

Campbell, R. B.↗
NASA NTRS1981

A Module Experimental Process System Development Unit (MEPSDU)

Design work for a photovoltaic module, fabricated using single crystal silicon dendritic web sheet material, resulted in the identification of surface treatment to the module glass superstrate which improved module efficiencies. A final solar module environmental test, a simulated hailstone impact test, was conducted on full size module superstrates to verify that the module's tempered glass superstrate can withstand specified hailstone impacts near the corners and edges of the module. Process sequence design work on the metallization process selective, liquid dopant investigation, dry processing, and antireflective/photoresist application technique tasks, and optimum thickness for Ti/Pd are discussed. A noncontact cleaning method for raw web cleaning was identified and antireflective and photoresist coatings for the dendritic webs were selected. The design of a cell string conveyor, an interconnect feed system, rolling ultrasonic spot bonding heat, and the identification of the optimal commercially available programmable control system are also discussed. An economic analysis to assess cost goals of the process sequence is also given.

Source record↗
NASA NTRS1982

Self-heated thermocouples for far-infrared detection

A novel self-heated Bi-Sb thermocouple for far-infrared detection has been developed. The detector is suitable for integration with monolithic antennas and imaging arrays. The device is fabricated in a single photolithography masking step using a photoresist-bridge technique. This bridge technique has also been used to make microbolometers with lower 1/f noise than those made by two conventional masking steps. The thermocouples have a noise equivalent power of 7 x 10 to the -10th W/sq rt of Hz and a 3-dB frequency response of 150 kHz.

Neikirk, D. P.↗
NASA NTRS1984

Ti/Pd/Cu Contacts for Semiconductor Devices

Copper systems equivalent in performance to silver or gold systems. Titanium layer and palladium layer deposited on semiconductor device by electron beam evaporation. Desired pattern etched using photoresist. Thin layer of copper plated on contact pattern from cyanide solution. Copper layer then built up to 4 to 8 microns by electroplatng from acid solution.

Campbell, R. B.↗
NASA NTRS1983

Non-noble metal based metallization systems

The results of efforts to produce a nonsilver metallization system for silicon photovoltaic cells are given. The system uses a metallization system based on molybdenum, tin, and titanium hydride. The initial work in this system was done using the MIDFILM process. The MIDFILM process attains a line resolution comparable to photoresist methods with a process related to screen printing. The surface to be processed is first coated with a thin layer of photopolymer material. Upon exposure to ultraviolet light through a suitable mask, the polymer in the non-pattern area crosslinks and becomes hard. The unexposed pattern areas remain tacky. The conductor material is then applied in the form of a dry mixture of metal which adheres to the tacky pattern area. The assemblage is then fired to ash the photopolymer and sinter the conductor powder.

Garcia, A., III↗
NASA NTRS1985

Analyzing Microchips With Dark-Field Negative Photomicrography

Inverse development process yields fine details. Photomicrographic technique produces images of integrated-circuit chips. Technique based on dark-field illumination: (chip lit with bright central spot of light and photographed by light scattered or diffracted from spot. Reveals more about microstructure patterns related to photoresist masking than more conventional bright-field method.

Suszko, S. F.↗
NASA NTRS1985

Thin-film Sensors for Space Propulsion Technology

SSME components such as the turbine blades of the high pressure fuel turbopump are subjected to rapid and extreme thermal transients that contribute to blade cracking and subsequent failure. The objective was to develop thin film sensors for SSME components. The technology established for aircraft gas turbine engines was adopted to the materials and environment encountered in the SSME. Specific goals are to expand the existing thin film sensor technology, to continue developing improved sensor processing techniques, and to test the durability of aircraft gas turbine engine technology in the SSME environment. A thin film sensor laboratory is being installed in a refurbished clean room, and new sputtering and photoresist exposure equipment is being acquired. Existing thin film thermocouple technology in an SSME environment are being tested. Various coatings and their insulating films are being investigated for use in sensor development.

Kim, W. S.↗
NASA NTRS1986

Room-Temperature Deposition of NbN Superconducting Films

Films with high superconducting transition temperatures deposited by reactive magnetron sputtering. Since deposition process does not involve significantly high substrate temperatures, employed to deposit counter electrode in superconductor/insulator/superconductor junction without causing any thermal or mechanical degradation of underlying delicate tunneling barrier. Substrates for room-temperature deposition of NbN polymeric or coated with photoresist, making films accessible to conventional lithographic patterning techniques. Further refinements in deposition technique yield films with smaller transition widths, Tc of which might approach predicted value of 18 K.

Thakoor, S.↗
NASA NTRS1986

Multifunction Vacuum Chamber for IC Metallization

Vacuum system chamber processing multilayer metallization on integrated circuits (IC's) performs four operations ordinarily done in separated equipment. Chamber etches holes, removes photoresist, cleans by sputter etching, and deposits final layer of metal. Combinedfunction chamber costs less than separate equipment. Chamber avoids exposing integrated circuits to room air and, to oxidation and dust, between steps. Eliminates time spent in transferring circuits from one apparatus to next.

Routh, D. E.↗
NASA NTRS1987

Optical emission from coupled surface plasmons

Surface plasmons on opposite sides of a thin metal film surrounded by identical dielectrics interact to form coupled surface plasmons (CSP's). Corrugation of the metal film permits interaction of the CSP's with the radiation field. This paper reports the observation of optical emission from CSP's excited by the near-field coupling of molecules adjacent to a corrugated thin metal film embedded in photoresist.

Gruhlke, R. W.↗
NASA NTRS1987

Luminal surface fabrication for cardiovascular prostheses

Methodology used for the production of highly ordered surfaces on polytetrafluoroethylene (PTFE) Teflon, for use of this material as a surface layer in small-diameter vascular prostheses, is described. Directed argon-ion beam sputter etching is used to produce highly ordered specific surface morphologies, and photolithographic techniques are used for pattern definition. The methodology also includes surface polishing of the samples, sputter deposition of the intermediary layer of gold to enhance photoresist adhesion and improve pattern resolution, and rotating of the sample to minimize the effects of ion-beam nonuniformity and asymmetry. Use of these techniques resulted in the formation of regular arrays of sharply defined hexagonal pillars with smooth vertical walls and large relief.

Deininger, William D.↗
NASA NTRS1988

Single-Layer, Multicolor Electroluminescent Phosphors

Etching eliminated in producing phosphor layers for displays. New process enables production of single-layer, two-color phosphor layer without etching. Method of construction, beginning with glass substrate with electrode and insulator layers, involves deposition of green phosphor masking with metal mask or photoresist; diffusion or ion implantation of manganese through mask to produce red phosphor and removal of mask.

Robertson, James B.↗
NASA NTRS1987

Integrated photo-responsive metal oxide semiconductor circuit

An infrared photoresponsive element (RD) is monolithically integrated into a source follower circuit of a metal oxide semiconductor device by depositing a layer of a lead chalcogenide as a photoresistive element forming an ohmic bridge between two metallization strips serving as electrodes of the circuit. Voltage from the circuit varies in response to illumination of the layer by infrared radiation.

Jhabvala, Murzban D.↗
NASA NTRS1989

Low-Dielectric Polyimides

New process developed to produce aromatic condensation polyimide films and coatings having dielectric constants in range of 2.4 to 3.2. Materials better electrical insulators than state-of-the-art commercial polyimides. Several low-dielectric-constant polyimides have excellent resistance to moisture. Useful as film and coating materials for both industrial and aerospace applications where high electrical insulation, resistance to moisture, mechanical strength, and thermal stability required. Applicable to production of high-temperature and moisture-resistance adhesives, films, photoresists, and coatings. Electronic applications include printed-circuit boards, both of composite and flexible-film types and potential use in automotive, aerospace, and electronic industries.

St. Clair, Anne K.↗
NASA NTRS1989

Process For Patterning Dispenser-Cathode Surfaces

Several microfabrication techniques combined into process cutting slots 100 micrometer long and 1 to 5 micrometer wide into tungsten dispenser cathodes for traveling-wave tubes. Patterned photoresist serves as mask for etching underlying aluminum. Chemically-assisted ion-beam etching with chlorine removes exposed parts of aluminum layer. Etching with fluorine or chlorine trifluoride removes tungsten not masked by aluminum layer. Slots enable more-uniform low-work function coating dispensed to electron-emitting surface. Emission of electrons therefore becomes more uniform over cathode surface.

Garner, Charles E.↗
NASA NTRS1986

Photoelectrochemical fabrication of spectroscopic diffraction gratings

Photoelectrochemical etching was demonstrated as a means of fabricating a variety of periodic structures in semiconductors. The semiconductor is used as an electrode in an electrochemical cell, and is in contact with a liquid electrolyte. When the crystal is held at a positive voltage and illuminated, etching occurs in only the illuminated regions to a depth proportional to the illumination intensity and exposure time. In Phase 1, it was determined that diffraction gratings could be produced in gallium arsenide crystals by this method, using either a scanned focused laser beam or by uniform illumination of a ruling mask defined in metal or photoresist on the crystal surface. The latter approach was determined to produce V-grooves if the mask is oriented along certain crystallographic directions. These V-grooves were produced with an exceedingly smooth crystal morphology due to the highly controllable nature of the process and the mild electrolytes involved. The results form the basis for photoelectrochemical fabrication of deep, low pitch Eschelle gratings for use in high orders in NASA spectrographic instrumentation such as the Space Telescope Imaging Spectrograph.

Rauh, R. David↗