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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

An oxygen pressure sensor using surface acoustic wave devices

Surface acoustic wave (SAW) piezoelectric devices are finding widespread applications in many arenas, particularly in the area of chemical sensing. We have developed an oxygen pressure sensor based on coating a SAW device with an oxygen binding agent which can be tailored to provide variable sensitivity. The coating is prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer which is then sprayed onto the surface of the SAW device. Experimental data shows the feasibility of tailoring sensors to measure the partial pressure of oxygen from 2.6 to 67 KPa (20 to 500 torr). Potential applications of this technology are discussed.

Leighty, Bradley D.↗
NASA NTRS1983

Application of surface acoustic wave devices to radio telemetry

Three experimental Surface Acoustic Wave Resonators (SAWR) are developed and evaluated. A desired center frequency is obtained by correct spacing of the Inter-Digital Transducers (IDT). Transmitting and receiving IDT's must be close for adequate coupling and a sufficient number of reflectors are required to create a high quality standing wave. A review of oscillator theory is given and current technology evaluated.

Strasilla, U.↗
NASA NTRS1995

ZnO films on /001/-cut (110)-propagating GaAs substrates for surface acoustic wave device applications

A potential application for piezoelectric films substrates is the monolithic integration of surface acoustic wave (SAW) devices with GaAs electronics. Knowledge of the SAW properties of the layered structure is critical for the optimum and accurate design of such devices. The acoustic properties of ZnO films sputtered on /001/-cut group of (110) zone axes-propagating GaAs substrates are investigated in this article, including SAW velocity, effective piezoelectric coupling constant, propagation loss, diffraction, velocity surface, and reflectivity of shorted and open metallic gratings. The measurements of these essential SAW properties for the frequency range between 180 and 360 MHz have been performed using a knife-edge laser probe for film thicknesses over the range of 1.6-4 micron and with films of different grain sizes. The high quality of dc triode sputtered films was observed as evidenced by high K(sup 2) and low attenuation. The measurements of the velocity surface, which directly affects the SAW diffraction, on the bare and metalized ZnO on SiO2 or Si3N4 on /001/-cut GaAs samples are reported using two different techniques: (1) knife-edge laser probe, (2) line-focus-beam scanning acoustic microscope. It was found that near the group of (110) zone axes propagation direction, the focusing SAW property of the bare GaAs changes into a nonfocusing one for the layered structure, but a reversed phenomenon exists near the (100) direction. Furthermore, to some extent the diffraction of the substrate can be controlled with the film thickness. The reflectivity of shorted and open gratings are also analyzed and measured. Zero reflectivity is observed for a shorted grating. There is good agreement between the measured data and theoretical values.

Hickernell, Frederick S.↗
NASA NTRS1995

ZnO Films on {001}-Cut <110>-Propagating GaAs Substrates for Surface Acoustic Wave Device Applications

A potential application for piezoelectric films on GaAs substrates is the monolithic integration of surface acoustic wave (SAW) devices with GaAs electronics. Knowledge of the SAW properties of the layered structure is critical for the optimum and accurate design of such devices. The acoustic properties of ZnO films sputtered on {001}-cut <110> -propagating GaAs substrates are investigated in this article, including SAW Velocity effective piezoelectric coupling constant, propagation loss. diffraction, velocity surface, and reflectivity of shorted and open metallic gratings. The measurements of these essential SAW properties for the frequency range between 180 and 360 MHz have been performed using a knife-edge laser probe for film thicknesses over the range of 1.6-4 micron and with films or different grain sizes. The high quality of dc triode sputtered films was observed as evidenced by high K(exp 2) and low attenuation. The measurements of the velocity surface, which directly affects the SAW diffraction, on the bare and metalized ZnO on SiO2, or Si3N4 on {001}-cut GaAs samples are reported using two different techniques: 1) knife-edge laser probe, 2) line-focus-beam scanning acoustic microscope. It was found that near the <110> propagation direction, the focusing SAW property of the bare GaAs changes into a nonfocusing one for the layered structure, but a reversed phenomenon exists near the <100> direction. Furthermore, to some extent the diffraction of the substrate can be controlled with the film thickness. The reflectivity of shorted and open gratings are also analyzed and measured. Zero reflectivity is observed for a shorted grating. There is good agreement between the measured data and theoretical values.

Kim, Yoonkee↗
NASA NTRS1973

Space manufacturing of surface acoustic wave devices, appendix D

Space manufacturing of transducers in a vibration free environment is discussed. Fabrication of the masks, and possible manufacturing of the surface acoustic wave components aboard a space laboratory would avoid the inherent ground vibrations and the frequency limitation imposed by a seismic isolator pad. The manufacturing vibration requirements are identified. The concepts of space manufacturing are analyzed. A development program for manufacturing transducers is recommended.

Sardella, G.↗
NASA NTRS1978

The study of surface acoustic wave charge transfer device

A surface acoustic wave-charge transfer device, consisting of an n-type silicon substrate, a thermally grown silicon dioxide layer, and a sputtered film of piezoelectric zinc oxide is proposed as a means of circumventing problems associated with charge-coupled device (CCD) applications in memory, signal processing, and imaging. The proposed device creates traveling longitudinal electric fields in the silicon and replaces the multiphase clocks in CCD's. The traveling electric fields create potential wells which carry along charges stored there. These charges may be injected into the wells by light or by using a p-n junction as in conventional CCD's.

Papanicolaou, N.↗
NASA NTRS1978

A monolithic SAW-charge transfer device

Surface acoustic waves excited in a Si-SiO2-ZnO layered structure can produce a traveling electric field in the silicon substrate. Charges stored in the traveling potential wells can be transferred at high speed and density and with less complexity. The monolithic structure under investigation for the SAW-charge transfer device consists of a silicon substrate, a thin silicon dioxide insulating layer on top of which a ZnO piezoelectric film is deposited by sputtering. The surface acoustic waves are excited by interdigital transducers. The signal charge is injected into traveling potential wells that travel with the velocity of sound. Conditions for the transfer of the charges by the traveling wells are analyzed. A surface acoustic wave program was used to determine the optimum structure dimensions and transducer configuration which will produce the highest coupling in the excitation of the piezoelectric waves.

Papanicolaou, N. A.↗
NASA NTRS2013

Temperature and Strain Coefficient of Velocity for Langasite SAW Devices

Surface Acoustic Wave sensors on Langasite substrates are being investigated for aerospace applications. Characterization of the Langasite material properties must be performed before sensors can be installed in research vehicles. The coefficients of velocity for both strain and temperature have been determined. These values have also been used to perform temperature compensation of the strain measurements.

Wilson, W. C.↗
NASA NTRS2010

Frequency coded sensors incorporating tapers

A surface acoustic wave device includes a piezoelectric substrate on which is formed a transducer that generates acoustic waves on the surface of the substrate from electrical waves received by the transducer. The waves are carried along an acoustic track to either a second transducer or a reflector. The transducers or transducer and reflector are formed of subsections that are constructed to operate at mutually different frequencies. The subsections of at least one of the transducers or transducer and reflector are out of alignment with respect to one another relative to the transverse of the propagation direction. The out of aligned subsections provide not only a frequency component but also a time to the signal output signal. Frequency response characteristics are improved. An alternative embodiment provides that the transducers and/or reflectors are continuously tapered instead of having discrete frequency subsections.

Hines, Jacqueline H.↗
NASA NTRS2015

Wireless SAW Sensors Having Integrated Antennas

A wireless surface acoustic wave sensor includes a piezoelectric substrate, a surface acoustic wave device formed on the substrate, and an antenna formed on the substrate. In some embodiments, the antenna is formed on the surface of the substrate using one or more of photolithography, thin film processing, thick film processing, plating, and printing.

Gallagher, Mark↗
NASA NTRS2012

Coded acoustic wave sensors and system using time diversity

An apparatus and method for distinguishing between sensors that are to be wirelessly detected is provided. An interrogator device uses different, distinct time delays in the sensing signals when interrogating the sensors. The sensors are provided with different distinct pedestal delays. Sensors that have the same pedestal delay as the delay selected by the interrogator are detected by the interrogator whereas other sensors with different pedestal delays are not sensed. Multiple sensors with a given pedestal delay are provided with different codes so as to be distinguished from one another by the interrogator. The interrogator uses a signal that is transmitted to the sensor and returned by the sensor for combination and integration with the reference signal that has been processed by a function. The sensor may be a surface acoustic wave device having a differential impulse response with a power spectral density consisting of lobes. The power spectral density of the differential response is used to determine the value of the sensed parameter or parameters.

Solie, Leland P.↗
NASA NTRS1999

Growth of Homoepitaxial ZnO Semiconducting Films

As a high temperature wide-band-gap (3.3 eV at room temperature) semiconductor, ZnO has been used for many applications such as wave-guides, solar cells, and surface acoustic wave devices, Since ZnO has a 60 meV excitonic binding energy that makes it possible to produce excitonic lasing at room temperature, a recent surge of interest is to synthesize ZnO films for UV/blue/green laser diodes. These applications require films with a smooth surface, good crystal quality, and low defect density. Thus, homoepitaxial film growth is the best choice. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystal substrates grown by the hydrothermal method are mechanically polished and annealed in air for four hours before the films are deposited. The annealing temperature-dependence on ZnO substrate morphology and electrical properties is investigated. Films are synthesized by off-axis reactive sputtering deposition. This produces films that have very smooth surfaces with roughness less than or equal to 5 nm on a 5 microns x 5 microns area. The full width at half maximum of film theta rocking curves measured by the x-ray diffraction is slightly larger than that of the crystal substrate. Films are also characterized by measuring resistivity, optical transmittance, and photoluminescence. The properties of ZnO films grown on (0001) ZnO and (0001) sapphire substrates will also be compared and discussed.

Zhu, Shen↗
NASA NTRS1999

Growth of Homoepitaxial ZnO Semiconducting Films

As a high temperature semiconductor, ZnO has been used for many applications such as wave-guide, solar cells, and surface acoustic wave devices. Since the ZnO material has an energy gap of 3.3 eV at room temperature and an excitonic binding energy (60 meV) that is possible to make excitonic lasering at room temperature a recent surge of interest is to synthesize ZnO films for electro-optical devices. These applications require films with a smooth surface, good crystal quality, and low defect density. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystals are grown by the hydrothermal method. Substrates are mechanically polished and annealed in air for four hours before deposited films. The annealing temperature-dependence of ZnO substrates is studied. Films are synthesized by the off-axis reactive sputtering deposition. The films have very smooth surface with a roughness </= 5 nm on a 5 micrometers x 5 micrometers area. The full width at half maximum of film theta rocking curves measured by the x-ray diffraction is slightly larger than the crystal substrate. The film quality is determined by measuring the film resistivity, the Hall mobility, carrier densities and the energy band gap. The properties of ZnO films grown of (0001) ZnO and (0001) sapphire substrates will be also compared and discussed in the presentation.

Zhu, Shen↗
NASA NTRS1973

Study for identification of Beneficial Uses of Space (BUS), phase 2. Volume 2: Technical report. Book 2: Section 5, appendices A through D

An investigation of the technology and programmatics involved in the development of four of the products selected as capable of benefitting from space manufacturing was conducted. The four activities selected are as follows: (1) levitation heating and melting of tungsten, (2) free suspension processing of oxides to form amorphous oxide materials, (3) crystals for surface wave acoustic substrates, and (4) space manufacturing of surface acoustic wave devices.

Source record↗
NASA NTRS1976

Methods utilized in evaluating the profitability of commercial space processing

Profitability analysis is applied to commercial space processing on the basis of business concept definition and assessment and the relationship between ground and space functions. Throughput analysis is demonstrated by analysis of the space manufacturing of surface acoustic wave devices. The paper describes a financial analysis model for space processing and provides key profitability measures for space processed isoenzymes.

Bloom, H. L.↗
NASA NTRS1994

Surface acoustic wave oxygen sensor

A surface acoustic wave (SAW) device that responds to oxygen pressure was developed by coating a 158 MHz quartz surface acoustic wave (SAW) device with an oxygen binding agent. Two types of coatings were used. One type was prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer containing the axial ligand. A second type was prepared with an oxygen binding porphyrin solution containing excess axial ligand without a polymer matrix. In the polymer based coatings, the copolymer served to provide the axial ligand to the oxygen binding agent and as a coating matrix on the surface of the SAW device. The oxygen sensing SAW device has been shown to bind oxygen following a Langmuir isotherm and may be used to measure the equilibrium constant of the oxygen binding compound in the coating matrix.

Collman, James P.↗