Showing papers in "Applied Physics Letters in 1980"
TL;DR: Ferroelectric smectic C (FSC) liquid crystals are used in a simple new geometry that allows the spontaneous formation of either of two surface-stabilized smective C monodomains of opposite ferroelectric polarization as discussed by the authors.
Abstract: Ferroelectric smectic C (FSC) liquid crystals are used in a simple new geometry that allows the spontaneous formation of either of two surface‐stabilized smectic C monodomains of opposite ferroelectric polarization. These domains are separated by well‐defined walls which may be manipulated with an applied electric field. The resulting electro‐optic effects exhibit a unique combination of properties: microsecond dynamics, threshold behavior, symmetric bistability, and a large electro‐optic response.
2,312 citations
TL;DR: In this paper, a new thermo-optical method based on the sensitive detection of thermal gradients adjacent to heated sample surfaces is described, and room and low-temperature experiments are performed using this technique, and its advantages over different methods are discussed.
Abstract: A new thermo‐optical method based on the sensitive detection of thermal gradients adjacent to heated sample surfaces is described. Room‐ and low‐temperature experiments were performed using this technique, and its advantages over different methods are discussed.
673 citations
TL;DR: In this paper, a second bulk compressional wave was observed in a water-saturated porous solid composed of sintered glass spheres using an ultrasonic mode conversion technique and the speed of this second wave was measured to be 1040 m/sec in a sample with 18.5% porosity.
Abstract: A second bulk compressional wave has been observed in a water‐saturated porous solid composed of sintered glass spheres using an ultrasonic mode conversion technique. The speed of this second compressional wave was measured to be 1040 m/sec in a sample with 18.5% porosity. The theory of Biot, which predicts two bulk compressional waves in porous media, provides a qualitative explanation of the observations. To the author’s knowledge, this type of bulk wave has not been observed at ultrasonic frequencies.
636 citations
TL;DR: In this paper, the authors compared the elastic wave speeds in a water-saturated porous structure of sintered glass beads with the predictions of Biot's theory and showed that the theoretical predictions lie within the bounds of experimental error (3%) for the fast compressional wave and for the shear wave.
Abstract: Plona’s recent measurements of elastic‐wave speeds in a water‐saturated porous structure of sintered glass beads are compared quantitatively to the predictions of Biot’s theory. The theoretical predictions lie within the bounds of experimental error (3%) for the fast compressional wave and for the shear wave in all cases. For the slow compressional wave, the theoretically predicted speeds lie within about 10% of the experimental values and increase with increase in porosity as observed. Our model achieves this agreement with no significant free parameters. The frame moduli are estimated using a recently developed self‐consistent theory of composite materials. The induced mass of the frame in a water environment is also estimated theoretically.
417 citations
TL;DR: In this article, the conduction band discontinuity ΔEc was found to be 0.248 eV, corresponding to about to 0.66 ΔEg rather than Dingle's commonly accepted value 0.85 Δ Eg, attributed to compositional grading during LPE growth.
Abstract: The Debye length smearing that occurs in C‐V profiling has precluded the use of C‐V profiling from an adjacent Schottky barrier to measure the magnitude of energy band discontinuities at barriers in isotype heterojunctions. It is observed, however, that in such a process both the number of the charge carriers and the moment of their distribution are conserved. This information permits the extraction of values for both the conduction band discontinuity ΔEc and any interface charge density. This technique and experimental results for an LPE‐grown n‐N GaAs‐Al0.3Ga0.7As heterojunction are described. We find ΔEc =0.248 eV, corresponding to about to 0.66ΔEg rather than Dingle’s commonly accepted value 0.85ΔEg . The difference is attributed to compositional grading during LPE growth.
355 citations
TL;DR: A generalization of the bounds obtained by Wiener and by Hashin and Shtrikman for complex dielectric constants is presented in this article, where the authors show how to derive the bounds for complex constants.
Abstract: A generalization of the bounds obtained by Wiener and by Hashin and Shtrikman is derived for complex dielectric constants.
276 citations
TL;DR: In this paper, the authors measured the dependence of the sliding friction coefficient on the water vapor content of a nitrogen atmosphere and found an increase of the coefficient with increasing humidity, with the coefficient ranging from 0.01 to 0.19.
Abstract: Hard diamondlike carbon layers have been deposited on silicon by rf plasma deposition using acetylene as working gas. For the first time the dependence of the sliding friction coefficient μ on the water vapor content of a nitrogen atmosphere was measured. An increase of μ with increasing humidity has been found, with μ ranging from 0.01 to 0.19. A steel ball was employed as the friction partner. The wear of the layers has been assessed by measuring their durability during friction experiments. It has been shown, contrary to other publications, that the durability has a maximum in the range 0.5–5.0% of relative humidity.
267 citations
TL;DR: In this paper, the reported noise-rise phenomenon observed in Josephson oscillators can be understood in terms of the full nonlinear and deterministic junction dynamics, and the drive damped pendulum equation describing the junction behavior exhibits chaotic solutions associated with the appearance of strange attractors in phase space.
Abstract: We suggest that the reported noise‐rise phenomenon observed in Josephson oscillators can be understood in terms of the full nonlinear and deterministic junction dynamics. We show that the drive damped pendulum equation describing the junction behavior exhibits chaotic solutions associated with the appearance of strange attractors in phase space. These results are relevant to the general problem of turbulent behavior of anharmonic systems.
251 citations
TL;DR: In this article, the Czochralski method was used to grow LiNbO3 crystals with periodic laminar ferroelectric domains whose half-period nearly corresponds to the coherence length.
Abstract: Using the Czochralski method we have grown LiNbO3 crystals with periodic laminar ferroelectric domains whose half‐period nearly corresponds to the coherence length. Quasi‐phase‐matching for the nonlinear optical coefficient d33 has been approximately realized and enhancement of second‐harmonic generation relative to conventionally phase‐matched crystals of the same length has been observed.
246 citations
TL;DR: In this paper, the photoresponse of high-defect-density amorphous semiconductors such as evaporated a−Si has been utilized to develop an electronic measurement capability which can generate and sample electronic transients with speeds ≲10 ps.
Abstract: The rapid relaxation of the photoresponse of high‐defect‐density amorphous semiconductors such as evaporated a‐Si has been utilized to develop an electronic measurement capability which can generate and sample electronic transients with speeds ≲10 ps.
245 citations
TL;DR: In this paper, a nonlinear optical processor using a photorefractive medium Bi12SiO20 and demonstrated that it is capable of convolving and correlating objects with spatial information.
Abstract: We report the application of four‐wave mixing to real‐time image processing. We constructed a nonlinear optical processor using a photorefractive medium Bi12SiO20 and demonstrated that it is capable of convolving and correlating objects with spatial information.
TL;DR: In this paper, the first observation of sharp photoluminescence lines with energies less than the energy of the recombination peak associated with the exciton bound to the neutral carbon acceptor in nominally undoped p-type GaAs grown by molecular beam epitaxy (MBE) is reported.
Abstract: The first observation of several sharp photoluminescence lines with energies less than the energy of the recombination peak associated with the exciton bound to the neutral carbon acceptor in nominally undoped p‐type GaAs grown by molecular beam epitaxy (MBE) is reported. The lines ranging from 1.5110 to 1.5040 eV are interpreted as radiative recombination of defect‐induced bound excitons directly correlated with the interaction of As4 molecular beam species during MBE growth. These lines disappear totally when As2 instead of As4 beams are used. We then demonstrate that all sharp photoluminescence features, previously only detected in the best LPE samples, are now also observed in thin MBE GaAs layers when grown from As2 beam species.
TL;DR: In this article, the authors derived the currentvoltage characteristics of photovoltaic cells based on the semiconductorelectrolyte junction and showed that the rate-limiting effect of charge transfer across the interface enhances the recombination rate in these regions with increasing voltage, thereby reducing the fill factor.
Abstract: Equations are derived giving the current‐voltage characteristics of photovoltaic cells based on the semiconductor‐electrolyte junction Recombinations in the neutral region and space‐charge region are included It is shown that the rate‐limiting effect of charge transfer across the interface enhances the recombination rate in these regions with increasing voltage, thereby reducing the fill factor Significant differences in the behavior of these cells and other photovoltaic cells are pointed out
TL;DR: In this article, the photoacoustic phase signal provided true thermal-wave imaging even in the presence of surface features with strong optical contrast, using piezoelectric detection and a modulation frequency of 185 kHz.
Abstract: Experiments on photoacoustic thermal‐wave microscopy are presented, for the first time, at high resolution. Using piezoelectric detection and a modulation frequency of 185 kHz, we obtain a thermal‐wave resolution of ∼7 μm. We show that the photoacoustic phase signal provides true thermal‐wave imaging even in the presence of surface features with strong optical contrast.
TL;DR: In this article, the authors performed thermal wave imaging of subsurface features in a metal using, for the first time, piezoelectric detection, and presented photoacoustic magnitude and phase images.
Abstract: We have performed thermal‐wave imaging of subsurface features in a metal using, for the first time, piezoelectric detection. Photoacoustic magnitude and phase images are presented.
TL;DR: In this paper, it was shown that films with low resistivity (∼4×10−4 Ω cm) and high optical transmission (≳85% between 4000 and 8000 A) can be prepared on low-temperature (40−180 °C) substrates with O2 partial pressures of (2 −7)×10 −5 Torr.
Abstract: High‐quality 800‐A‐thick films of tin‐doped indium oxide have been prepared by magnetron sputtering. It is shown that films with low resistivity (∼4×10−4 Ω cm) and high optical transmission (≳85% between 4000 and 8000 A) can be prepared on low‐temperature (40–180 °C) substrates with O2 partial pressures of (2–7)×10−5 Torr.
TL;DR: In this article, the authors show that the widely accepted formula for the angular response function is inadequate and must be multiplied by cosϑ, and good agreement with experiment is then obtained.
Abstract: An important criterion in the design of transducer array elements for acoustic imaging is the angular response, or the far‐field radiation pattern, of a single element. In this letter, we show that the widely accepted formula for the angular response function is inadequate and must be multiplied by cosϑ. Good agreement with experiment is then obtained.
TL;DR: In this paper, low-dark-current IN0.53GA0.47 photodiodes have been shown to have a soft breakdown property at higher voltages, resulting in the soft breakdown characteristic widely observed in these materials.
Abstract: We report on low‐dark‐current IN0.53GA0.47As photodiodes in which generation‐recombination current dominates diode leakage up to as high as 100 V. At higher voltages, tunneling currents become dominant, resulting in the soft breakdown characteristic widely observed in these materials. The dark current versus voltage characteristics have been fit to variations in current of over six orders of magnitude and a temperature range greater than 150 K using a theory which includes generation‐recombination, tunneling, and shunt components.
TL;DR: The linewidth dependence of electromigration damage has been evaluated for 2.5 cm−long, 1−4μm−wide, e−gun-evaporated Al−0.5%Cu conductions as mentioned in this paper.
Abstract: The linewidth dependence of electromigration damage has been evaluated for 2.5‐cm‐long, 1–4‐μm‐wide, e‐gun‐evaporated Al‐0.5%Cu conductions. It is observed that the ≲1‐μm lines are much longer lived than the ≳2‐μm lines, reversing the trend at wider widths. These results are rationalized on the basis of the ’’bamboo’’‐type grain structure of narrow lines in contrast to the much more heterogeneous structure of the wider meanders.
TL;DR: In this paper, the electrical activity of point defects is neutralized by reaction with atomic hydrogen at 200 ˚°C and the point defects are observed by capacitance transient spectroscopy.
Abstract: Laser melting of crystalline silicon introduces electrically active defects which are observed by capacitance transient spectroscopy. The electrical activity of these point defects is neutralized by reaction with atomic hydrogen at 200 °C.
TL;DR: In this paper, a single-crystalline aluminum nitride film is grown on a basalplane sapphire substrate and the c-axis oriented films are grown on glass and gold-film substrates at substrate temperatures as low as from 50 to 500 °C by using reactive rf planar magnetron sputtering.
Abstract: A single‐crystalline aluminum nitride film is grown on a basal‐plane sapphire substrate and the c‐axis‐oriented films are grown on glass and gold‐film substrates at substrate temperatures as low as from 50 to 500 °C by using reactive rf planar magnetron sputtering. Surface acoustic waves are generated in both structures where interdigital transducers are located on the top of an aluminum nitride film and at the interface between the film and the substrate sapphire. The effective surface acoustic wave coupling factor k2 is 0.09 and 0.12%, respectively, for these interdigital transducer configurations. The aluminum nitride films sputtered on a gold film on a glass rod and on a glass sheet itself are also piezoelectric and used as bulk and surface acoustic wave transducers, respectively. These piezoelectric aluminum nitride films on glass and metal‐film substrates have become available for the first time because film growth at low temperature has become possible in the present study.
TL;DR: In this article, the authors used 1.0 μm of SiO evaporated onto Al. The desired reflectance profile was approximated with a 1.5 μm SiO evaporation.
Abstract: Efficient radiative cooling is feasible with surfaces which radiate predominantly in the 8–13‐μm wavelength range, where the atmosphere emittance is low. The desired reflectance profile was approximated with 1.0 μm of SiO evaporated onto Al. It results from strong lattice absorption in SiO in conjunction with destructive interference. Refrigeration to 40 K below the ambient appears to be possible under suitable climatic conditions.
TL;DR: In this paper, the growth of CoSi2 films on Si substrates and Si films on the Si(111)/CoSi2 structure are investigated and two dominant factors required to obtain good epitaxial films are substrate cleaning by lamp heating before the film deposition and annealing of the deposited films without exposure to air.
Abstract: Epitaxial growth of CoSi2 films on Si substrates and the growth of Si films on the Si(111)/CoSi2 structure are investigated. Solid phase epitaxy is used to grow both CoSi2 and Si films. Molecular beam epitaxy is also used to grow the top Si films in the double heteroepitaxy. It has been found that two dominant factors required to obtain good epitaxial films are substrate cleaning by lamp heating before the film deposition and annealing of the deposited films without exposure to air. Excellent crystalline quality of the CoSi2 films on (111) Si substrates and good quality of the Si films on the Si(111)/CoSi2 structure have been demonstrated by ion channeling and backscattering techniques and reflection electron diffraction analysis. Uniformity of the grown films has also been examined by scanning electron microscopy.
TL;DR: In this paper, a bulk acoustic-wave high-Q resonators and acoustically coupled resonator filters have been fabricated and operated at their fundamental half-wavelength mode in the 200-500 MHz frequency range.
Abstract: Novel bulk acoustic‐wave high‐Q resonators and acoustically coupled resonator filters have been fabricated and operated at their fundamental half‐wavelength mode in the 200‐500‐MHz frequency range. These structures are fabricated on thin ZnO/silicon diaphragms with dimensions small enough to be incorporated within integrated circuits. Resonator Q’s near 2600 at the fundamental mode have been obtained and strong inter‐resonator acoustic coupling has been achieved yielding filters having insertion loss (untuned) as low as 5.5 dB.
TL;DR: In this paper, the authors report the generation of pulses as short as 5 psec in duration by passive mode locking of a modified strip buried heterostructure GaAlAs diode in an extended resonator.
Abstract: We report the generation of pulses as short as 5 psec in duration by passive mode locking of a modified strip buried heterostructure GaAlAs diode in an extended resonator. We also describe the effects of intercavity bandwidth control for the generation of transform‐limited pulses. E/T;8042.80.−f, 42.55.Px
TL;DR: In this article, NiSi2 and CoSi2 layers have been grown on crystalline silicon by molecular beam epitaxy (MBE) and shown to be highly crystalline films can be grown by either silicon-metal codeposition or by pure metal deposition on substrates heated to 550-800°C.
Abstract: Epitaxial NiSi2 and CoSi2 layers have been grown on crystalline silicon by molecular beam epitaxy (MBE) Stoichiometric, highly crystalline films can be grown by either silicon‐metal codeposition or by pure metal deposition on substrates heated to 550–800 °C Crystalline quality is relatively insensitive to deposition conditions Film smoothness is maximized by codeposition at temperatures near 600 °C Both silicides have been epitaxially overgrown with silicon producing a fully crystalline silicon/metal silicide/silicon heterostructure
TL;DR: In this article, the authors show that the generation of radiative recombination centers increases with increasing temperature, and that all the light-induced centers disappear upon thermal anneal at about 210°C.
Abstract: Laser irradiation of hydrogenated amorphous silicon produces recombination centers which shorten the lifetime of carriers. Some of the light‐induced centers are radiative. The generation of the new radiative recombination centers increases with increasing temperature. All the light‐induced centers disappear upon thermal anneal at about 210 °C.
TL;DR: In this article, the formation of silicides from thin films of the rare earth (or related) elements Y, Tb, and Er, on both (100) and (111) Si substrates, has been investigated simultaneously with backscattering and x-ray diffraction.
Abstract: The formation of silicides from thin films of the rare‐earth (or related) elements Y, Tb, and Er, on both (100) and (111) Si substrates, has been investigated simultaneously with backscattering and x‐ray diffraction. The silicon‐rich compounds of the type R‐ESi2−n form almost directly with no, or only poorly distinct formation of other silicides at temperatures from about 300 to 500 °C. For all three metals, the reactions with (111) Si require temperatures some 100 °C higher than the reactions with (100) Si, a difference in behavior which is quite important considering the relatively low reaction temperatures. The reactions of Er and Tb with (100) Si are quite sudden, indicating that nucleation is probably the controlling mechanism.
TL;DR: In this paper, a carbonized photoresist mask with narrow, widely spaced stripe openings is first deposited on a reusable GaAs substrate. Epitaxial growth initiated within the openings, followed by lateral growth over the mask, produces a continuous single-crystal GaAs film.
Abstract: Using a new technique, which we have named the CLEFT process (cleavage of lateral epitaxial films for transfer), we have grown single‐crystal GaAs films by vapor phase epitaxy (VPE) on reusable GaAs substrates. A carbonized photoresist mask with narrow, widely spaced stripe openings is first deposited on a (110) GaAs substrate. Epitaxial growth initiated within the openings, followed by lateral growth over the mask, produces a continuous single‐crystal GaAs film. The upper surface of the film is bonded to a glass substrate, and the film is then cleaved from the GaAs substrate, leaving the surface of the latter in condition for repeating the procedure. The same GaAs substrate has been used for successive growth of four GaAs films, each about 4 cm2, ranging in thickness from 5 to 10 μm. The electrical properties of a CLEFT film were found comparable to those of conventional VPE layers. The CLEFT process should also be applicable to other semiconductors.
TL;DR: In this paper, the role of diffusion barriers in the contact metallurgy of silicon semiconductor devices is to prevent silicon diffusion into the top layer of the metallization process.
Abstract: The role of diffusion barriers in the contact metallurgy of silicon semiconductor devices is to prevent silicon diffusion into the top layer of the metallization. It is shown that TiN and TaN are good diffusion barriers in metallization schemes which consist of a silicide layer for contact to the silicon and a top layer of nickel for soldering purposes. With these diffusion barriers, the contacts are stable under annealing up to 600 °C.