摘要:

The pressure pulse generated by an electric arc discharge in aqueous liquids was measured with a lithium niobate piezoelectric transducer. These measurements are the first time‐resolved pressure pulses recorded in proximity to an arc channel.

ISSN:0003-6951    

DOI:10.1063/1.88416

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

We observed an anomalous temperature effect in the growth of oxidation stacking faults in silicon. For a given oxidation time, the size of stacking faults first increases with temperature following an Arrhenius relation, reaches a peak at some temperature, and then decreases with temperature rather sharply until, finally, the faults totally vanish. The temperature above which the oxidation stacking faults vanish is dependent on the crystal surface orientation as well as on the oxidation ambients. In dry oxygen, this temperature is ∼1240 °C for {100} surfaces, ∼1220 °C for {111} surfaces, and ∼1175 °C for {1,0,11} surfaces (5° off {100}). Thus, the size‐versus‐temperature curve of the growth of oxidation stacking faults can be divided into two regions, which may be called the growth and the retrogrowth regions. In the growth region the growth follows a power law of (size) ∝ (time)0.8; in the retrogrowth region, the power law breaks down. The activation energy in the growth region is 2.3 eV for all surface orientations and oxidation ambients. A more complete picture of the growth of stacking faults emerges, in which the reported ’’immunity to stacking faults’’ of certain vicinal {100} surfaces is merely a point far out in the retrogrowth region.

ISSN:0003-6951    

DOI:10.1063/1.88441

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

We report an experiment on acoustic surface wave storage in photoconducting CdS which leads to a decay time as long as 100 ms. Both charging and storing times are deduced from the experimental amplitude of the echo restored by a readout pulse. In addition we find that charging and discharging of the memory seem to obey a two‐step process.

ISSN:0003-6951    

DOI:10.1063/1.88442

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The storage, correlation, and coherent integration of analog signals in a Schottky diode acoustoelectric memory correlator is described. The experiments demonstrate storage of phase and amplitude of a 70‐MHz signal by the distribution of charge in an array of Schottky diodes. Coherent integration is obtained by accumulating a succession of charges in highly resistive polycrystalline silicon islands. Coherent integration over a time period of several tens of milliseconds is reported.

ISSN:0003-6951    

DOI:10.1063/1.88443

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Electron microscopic evidence is obtained for the presence of a possible two‐phase structure inside the &ggr;‐phase field of the Cu‐Al system. Alloys with composition 34.54 at.% Al show a banded microstructure. When the bands are observed edge on adjacent plates differ in brightness. They are visible as fringe patterns when lying in planes inclined to the foil plane. Electron diffraction experiments show that the only crystallographic difference between two adjacent plates is the size of the unit cell. The probable composition of the coexisting phases is suggested to be Cu9Al4and Cu17Al9.

ISSN:0003-6951    

DOI:10.1063/1.88444

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A method of obtaining rocking‐beam microarea electron diffraction patterns is described employing the electron optics of a single‐field condenser‐objective lens in a commercial scanning transmission electron microscope. Theoretical and experimental evidence is presented showing that it is possible to obtain diffraction patterns from areas less than 3 nm in diameter with minimum lattice spacings of 0.14 nm. This is demonstrated with a specimen consisting of small gold particles evaporated on a carbon substrate.

ISSN:0003-6951    

DOI:10.1063/1.88417

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The phase‐contrast method of visualizing transparent objects is applied to ultrasonic imaging. In this method a thin polyethylene phase plate is placed at the back focal plane of an acoustic object lens which causes velocity variations in the object to be converted to proportional amplitude variations at the image plane. Examples of the application of this method to image acoustically transparent (i.e., nonabsorbing) structures, using a recently developed system to visualize ultrasonic waves, are presented.

ISSN:0003-6951    

DOI:10.1063/1.88418

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An optical image is converted into an electrical signal by utilizing acoustic surface wave convolution in a monolithic structure composed of a piezoelectric zinc oxide film on a silicon substrate. Measurements are presented describing the variation of convolution efficiency with light intensity, input acoustic power, and convolver gate electrode dc bias. An initialization procedure is described that allows the device to operate either in an image memory mode or in a nonstorage mode which permits scanning of nonstationary images.

ISSN:0003-6951    

DOI:10.1063/1.88419

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Photocurrent and differential capacitance were measured as a function of terminal potential with CdS‐ and GaAs‐electrolyte photovoltaic cells to determine the open‐circuit voltageVocand the power conversion efficiency &eegr;p.Vocwas found to be 1.2 V for both cells. With monochromatic excitation, &eegr;p=32% for the CdS cell, and &eegr;p=21% for the GaAs cell. For both cells the quantum efficiency was larger than unity at short wavelengths indicating that current doubling is occurring at the interface. For the GaAs cell, current flow is mostly due to the diffusion of minority carriers from the bulk to the space‐charge layer under illumination.

ISSN:0003-6951    

DOI:10.1063/1.88420

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A nonturbulent mechanism is proposed whereby a rotating electron or ion beam pulse rapidly deposits energy on the ions of a dense, magnetized, weakly collisional plasma through excitation of the compressional Alfve´n mode.

ISSN:0003-6951    

DOI:10.1063/1.88421

出版商:AIP    

年代:1975

数据来源: AIP