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  • 1
    Electronic Resource
    Electronic Resource
    Photothermal measurements of high Tc superconductors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 598-599 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a photothermal method for making point measurements of the thermal conductivities of high Tc superconductors. Images made at room temperature on polycrystalline materials show the thermal inhomogeneities. Measurements on single-crystal Bi2Sr2CaCu2Ox compounds reveal a very large anisotropy of about 7:1 in the thermal conductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101843
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  • 2
    Electronic Resource
    Electronic Resource
    In situ ultrasonic monitoring of photoresist development (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2215-2217 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed an in situ method to measure the change in thickness of photoresist during development. The phase of a high frequency ultrasound signal is monitored as it is reflected from the silicon/photoresist interface during resist development. The method was tested using a 1.5 μm film of Shipley 1811 resist. The total phase change during development of 19° was consistent with theoretical calculations at 280 MHz, and this change was used to obtain the resist thickness during development. The method was used to find the development rate of this positive-tone resist as a function of exposure dose in the 20–68 mJ/cm2 range. As expected, there was an increase in development rate as the exposure time increased; this continued up to about 40 s of exposure, beyond which the rates were essentially unchanged. Measurements on a wafer with microelectronic devices ranging in topography from 0.10 to 1.0 μm show that the method is applicable to wafers with typical circuit topography. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122427
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  • 3
    Electronic Resource
    Electronic Resource
    Nozzleless droplet formation with focused acoustic beams (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3441-3447 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the use of focused acoustic beams to eject discrete droplets of controlled diameter and velocity from a free-liquid surface. No nozzles are involved. Droplet formation has been experimentally demonstrated over the frequency range of 5–300 MHz, with corresponding droplet diameters from 300 to 5 μm. The physics of droplet formation is essentially unchanged over this frequency range. For acoustic focusing elements having similar geometries, droplet diameter has been found to scale inversely with the acoustic frequency. A simple model is used to obtain analytical expressions for the key parameters of droplet formation and their scaling with acoustic frequency. Also reported is a more detailed theory which includes the linear propagation of the focused acoustic wave, the coupling of the acoustic fields to the initial surface velocity potential, and the subsequent dynamics of droplet formation. This latter phase is modeled numerically as an incompressible, irrotational process using a boundary integral vortex method. For simulations at 5 MHz, this numerical model is very successful in predicting the key features of droplet formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342663
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature measurement in rapid thermal processing using acoustic techniques (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 974-976 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Acoustic techniques are used to monitor the temperature of silicon wafers during rapid thermal processing from room temperature to 1000 °C with ±5 °C accuracy. Acoustic transducers are mounted at the bases of the quartz pins that hold up the silicon wafer during rapid thermal processing. An electrical pulse applied across a transducer generates an extensional mode acoustic wave guided by the quartz pins. The extensional mode is converted into Lamb waves in the silicon wafer which acts as a plate waveguide. The Lamb waves propagate across the length of the silicon wafer and are converted back into an extensional mode in the opposite pin. The time of flight of the extensional mode in the quartz pins is measured using pulse echo techniques and is subtracted from the total time of flight to obtain the Lamb wave time of flight across the wafer. Because the velocity of Lamb waves in the silicon wafer is systematically affected by temperature, the measurement of the time of flight of the Lamb wave provides the accurate temperature of the silicon wafer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144929
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  • 5
    Electronic Resource
    Electronic Resource
    Micromachined 1–3 composites for ultrasonic air transducers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2095-2098 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Airborne ultrasound has many applications, such as robotic sensing, NDE, and gas flow measurements. Coupling of ultrasound into air from plane piston piezoelectric transducers is inefficient because of the large impedance mismatch between the piezoelectric and air, and the lack of appropriate matching materials. Standard design practice requires the use of a matching layer material with an acoustic impedance of approximately 0.02 MRayls and a thickness of a quarter-wavelength. Such materials are not readily available. A method to manufacture low impedance materials using micromachining techniques for matching piezoelectrics into air are presented here. These materials are capped 1–3 composites of air and Kapton(R). The acoustic effect of the cap is significant and necessitates a modified design technique. This technique involves the use of two matching layers with inverted acoustic impedances. Using the new fabrication technology and the new design technique, an 860-kHz transducer was fabricated with a one-way insertion loss of 17 dB and a fractional 3 dB bandwidth of 6%. It is believed that, using this technology, a transducer with a one-way insertion loss of 10 dB and a fractional bandwidth of 10% is possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145231
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Amplitude and phase acoustic microscope using digital heterodyning (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1236-1242 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have built a low-frequency (3–10 MHz) scanning acoustic microscope (SAM) that measures amplitude and phase of rf tone bursts quickly and accurately. The amplitude has a 70-dB dynamic range; the phase is measured to better than 0.1°. The electronics are capable of operating at greater than a 100-kHz repetition rate. The signal is mixed with a reference that is shifted discretely in-phase between tone bursts, the product is integrated and digitized, and the amplitude and phase are computed using at least three digitized values. This general technique operates at a rate limited by the digitizer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141217
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  • 7
    Electronic Resource
    Electronic Resource
    A noncontacting technique for measuring surface tension of liquids (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2048-2050 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a novel instrument for measuring the surface tension of liquids. It utilizes ultrasonic and optical methods to excite and detect a capillary wave packet. A focused ultrasonic transducer is used to generate a mound on the surface of a liquid. Capillary waves propagate radially outward from the mound, and a noncontacting confocal optical microscope measures the amplitude of the wave packet at any distance away from the excitation point. We invert the measured wave amplitude to obtain the dispersion relation of the capillary waves and hence the surface tension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143164
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  • 8
    Electronic Resource
    Electronic Resource
    Lamb wave devices using capacitive micromachined ultrasonic transducers (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 111-113 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lamb wave devices based on capacitive micromachined ultrasonic transducers (CMUTs) have been built on 500-μm-thick silicon wafers for frequencies in the vicinity of 1 MHz. CMUTs have been used to both excite and detect Lamb waves in the substrate. This configuration eliminates the need for piezoelectric materials, which are not compatible with the existing integrated circuit (IC) fabrication techniques, and allows easy integration of Lamb wave devices and electronics on the same wafer. Finite element analysis of the devices shows that the lowest order antisymmetric Lamb wave (A0) is the dominant mode in the substrate in this frequency range. This result is also confirmed by demonstration experiments. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337647
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  • 9
    Electronic Resource
    Electronic Resource
    Ultrasonic excitation and detection of capillary waves for the measurement of surface film properties (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1571-1572 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 10 MHz focused ultrasonic transducer is used to excite capillary waves by placing its focus at the air-water interface and using a tone burst to excite the ultrasonic wave. The radiation pressure associated with the upward propagating ultrasonic pulse lifts the surface of the water which then relaxes by exciting a radially propagating capillary wave. An amplitude and phase measuring acoustic microscope operating at 10 MHz is used to detect the amplitude and slope of the capillary wave as it propagates over the focused transducer of the acoustic microscope. This arrangement allows us to make a noncontacting measurement of surface tension and surface viscosity which will be used for characterizing surface films, such as the marine microlayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99084
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  • 10
    Electronic Resource
    Electronic Resource
    Surface defect inspection of spherical objects by the resonant sphere technique (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1815-1817 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ceramic materials, such as silicon nitride and silicon carbide, are important because of their high mechanical strength at high temperature and in nonlubricative environments. The weakness of these materials lies in their brittleness. Stress concentration caused by the existence of surface or subsurface cracks can lead to the total mechanical failure of parts. In this letter, we describe the application of the resonant-sphere technique to perform nondestructive evaluation of ceramic bearing balls. The technique had been shown to be capable of measuring various material properties, such as Vs (shear wave velocity) and ν (Poisson's ratio). We use phase and amplitude measurements to simplify the evaluation of various resonance quality factors (Q), and we present, for the first time, the use of a resonance technique to propagate and detect surface waves on a sphere. We also show a decrease in Q for surface-wave modes due to the existence of surface cracks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107173
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