摘要:

Dielectric and piezoelectric responses caused by a high electric field and a 10‐Hz small strain have been simultaneously measured for stretched polyvinylidene fluoride using a minicomputer system. The electric field was applied up to 240 MV/m in a sinusoidal or triangular wave form in the frequency range 10−4–10−2Hz at temperatures between −100 and 100 °C. Ferroelectric hysteresis loops were observed even below the glass‐transition temperature of −60 °C. At 20 °C the 120‐MV/m electric field gave the remanent polarizationProf 50 mC/m2which resulted in the piezoelectric activitiese31ande32of 70 and 7.5 mC/m2, respectively. The origin ofPrwas confirmed to be the molecular dipole orientation because the value ofPrwas independent of the frequency of applied field. The coercive fieldEcsignificantly decreased with increasing temperature from 180 MV/m (−100 °C) to 25 MV/m (100 °C), whilePrshowed only a slight temperature dependence.

ISSN:0021-8979    

DOI:10.1063/1.327723

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Transverse and longitudinal elastic strain have been measured for electric fields applied along the ⟨100⟩ direction in single crystals of lead magnesium niobate [Pb(Mg1/3Nb2/3)03], using a bonded strain gauge technique. A quadratic electrostrictive relation holds between induced elastic strain and electric polarization for temperatures near the low‐frequency dielectric maximum. The electrostriction coefficients are almost temperature independent with values Q11=2.50×10−2m4/C2and Q12=−0.96×10−2m4/C2. To check the direct measurements, the hydrostaticQcoefficient was determined independently by measuring the pressure dependence of the dielectric permittivity. The valueQh=0.60×10−2m4/C2obtained is in good agreement with that calculated from the direct measurements.

ISSN:0021-8979    

DOI:10.1063/1.327724

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The transmission behavior of 90‐ns CO2laser pulses through germanium has been studied at high intensities up to 20 MW/cm2. With increasing incident intensity, the transmitted intensity was observed to saturate quite abruptly at a level which decreased with increase in crystal length. The saturated level of transmitted intensity was found to be higher at lower temperatures. The observed transmission behavior is interpreted in terms of multiphoton absorption across the direct band gap, followed by absorption by the excess carriers thus generated. By fitting experimental data to a phenomenological model, a room‐temperature seven‐photon absorption coefficient of 1.5×10−9(cm2/MW)6cm−1is obtained for germanium in the 10‐&mgr;m region.

ISSN:0021-8979    

DOI:10.1063/1.327725

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The scanning photoacoustic microscope (SPAM) is used in both the conventional and phase‐contrast modes to detect a well‐characterized subsurface flaw in Al. The physical mechanism is that of thermal diffusion, with a subsurface probe depth and flaw resolution length of approximately one thermal‐diffusion length. Comparison of the dependences of the photoacoustic signal upon chopping frequency from the different regions of the sample confirm that the differential signal from the flaw corresponds to a transition from thermally thick to thermally thin boundary conditions. Experimental results are in good agreement with calculations based upon a three‐dimensional thermal‐diffusion model.

ISSN:0021-8979    

DOI:10.1063/1.327726

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Optical absorption of phosphorus‐doped polycrystalline Si films observed at photon energies below the energy gap has been interpreted in terms of free‐carrier absorption, which obeys the Drude theory. As a result, we can simultaneously determine conductivity, electron mobility, and carrier concentration of heavily doped polycrystalline Si films from their optical transmission spectra alone. The new technique offers a contactless measurement of electrical properties for heavily doped polycrystalline Si thin films.

ISSN:0021-8979    

DOI:10.1063/1.327733

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Optical absorption in polystyrene and poly(methyl methacrylate) was measured in the visible region of radiation. Two methods of data evaluation yield consistent results to indicate that near &lgr;=500 nm, the absorption coefficient is approximately 2×10−4cm−1, or less than 100 dB/km, for both materials.

ISSN:0021-8979    

DOI:10.1063/1.327682

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The ac thin‐film electroluminescence devices employing ZnS : Mn as the active medium exhibit a ’’memory effect’’ which in turn is related to filamentary luminescence. Under certain film preparation and device excitation conditions, it is found that the filaments exhibit a large scale cooperative motion. Spontaneously moving spirals and stripes have been observed under steady‐state conditions. This paper describes the phenomena, and a thermal model for the observations is proposed.

ISSN:0021-8979    

DOI:10.1063/1.327683

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Holes were drilled through 330‐&mgr;‐thick single‐crystal sapphire wafers with a pulsed laser beam. The hole exit positions on one face of the wafer were found to have undergone a random‐walk displacement relative to the entrance hole positions on the opposing face of the wafer. This random displacement increased with the number of laser pulses required to drill through the wafer. A model in which the bottom of the drill hole experiences small random displacements during each laser pulse was used to describe the experimental observations. The model indicates that the average random displacement caused by each laser pulse is only a few percent of the hole diameter. Laser‐drill‐hole wandering can be minimized by using as few laser pulses as necessary to drill through the sapphire wafers while at the same time avoiding the cracking and spalling of the wafer that occur with a hole drilled through the wafer with a single pulse.

ISSN:0021-8979    

DOI:10.1063/1.327684

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Retention and re‐emission of 125– 1000–eV D+ions in stainless steel has been measured at 90, 300, and 500 °K. Saturation of retained fluence in a 90 °K target occurs when there is approximately one retained atom for every metal atom within the range of this projectile. Implantation at 300 and 500 °K shows saturation at densities three to five times smaller than the low‐temperature implant. Backscattering coefficients are determined to range from 0.5 at 125 eV to 0.3 at 1 keV; these are consistent with computer simulations. Thermally induced re‐emission of deuterium retained after bombarding a room temperature target has a diffusive character with an activation energy of 14.7 kcal/mole.

ISSN:0021-8979    

DOI:10.1063/1.327685

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A time‐of‐flight atom‐probe field‐ion microscope has been developed which uses nanosecond laser pulses to field evaporate surface species. The ability to operate an atom‐probe without using high‐voltage pulses is advantageous for several reasons. The spread in energy arising from the desorption of surface species prior to the voltage pulse attaining its maximum amplitude is eliminated, resulting in increased mass resolution. Semiconductor and insulator samples, for which the electrical resistivity is too high to transmit a short‐duration voltage pulse, can be examined using pulsed‐laser assisted field desorption. Since the electric field at the surface can be significantly smaller, the dissociation of molecular adsorbates by the field can be reduced or eliminated, permitting well‐defined studies of surface chemical reactions. In addition to atom‐probe operation, pulsed‐laser heating of field emitters can be used to study surface diffusion of adatoms and vacancies over a wide range of temperatures. Examples demonstrating each of these advantages are presented, including the first pulsed‐laser atom‐probe (PLAP) mass spectra for both metals (W, Mo, Rh) and semiconductors (Si). Molecular hydrogen, which desorbs exclusively as atomic hydrogen in the conventional atom probe, is shown to desorb undissociatively in the PLAP. Field‐ion microscope observations of the diffusion and dissociation of atomic clusters, the migration of adatoms, and the formation of vacancies resulting from heating with a 7‐ns laser pulse are also presented.

ISSN:0021-8979    

DOI:10.1063/1.327686

出版商:AIP    

年代:1980

数据来源: AIP