Volume 21, Issue 12, 15 December 1972
Index of content:
21(1972); http://dx.doi.org/10.1063/1.1654258View Description Hide Description
A copper vapor laser, utilizing a pulsed discharge transverse to a supersonic flow of copper vapor, argon, and helium and oscillating at 5106 and 5782 Å, has been built and tested. Laser energy densities per pulse of 2.5 μJ cm−3 have been achieved to date. Laser pulse widths of up to 185 nsec have been obtained with delay times after initiation of the current pulse of 220–250 nsec. Both the delay time and pulse width are in good agreement with theoretical predictions. Quenching of the laser pulse is shown to be due to a rapid increase in the rate of equilibration of the lasing levels by electron collisions, and to a decrease in the differential pumping of the lasing levels from the ground state because of a decay in the electron temperature.
21(1972); http://dx.doi.org/10.1063/1.1654260View Description Hide Description
In a uniaxial crystal, walk‐off or double refraction occurs only in the plane of the direction of propagation and the optic axis. By elliptical focusing of the signal, idler, and pump we can focus much more tightly in the non‐walk‐off plane and increase parametric gain considerably. Optimum focusing conditions are obtained, and in a typical LiNbO3 oscillator pumped with 1.06 μ we find that threshold can be lowered more than a factor of 5.
Electronic superposition of sample current and secondary‐electron images in Auger electron spectroscopy21(1972); http://dx.doi.org/10.1063/1.1654261View Description Hide Description
Selected‐area analysis by Auger electron spectroscopy requires a knowledge of electron‐beam location and the ability to place the beam on specified areas quickly and reproducibly. For samples with both conducting and insulating regions, it is highly desirable to use a grazing‐angle‐of‐incidence electron beam to reduce surface‐charging effects. Unfortunately, the use of grazing incidence makes the location of the area of interest and simultaneous optimization of the Auger signal rather difficult because of a parallax problem. Superposition of sample current images and secondary‐electron images produced by scanning the electron beam from the grazing‐incidence gun provides a solution to these alignment problems.
21(1972); http://dx.doi.org/10.1063/1.1654262View Description Hide Description
We have developed a theory to solve for the lowest‐order mode of hollow dielectriclaser resonators with external mirrors. The results agree well with previously reported experimental results. In general, the optimum position (or positions) for a mirror of fixed curvature can be calculated, but as yet no simple rule has been found for predicting these positions.
21(1972); http://dx.doi.org/10.1063/1.1654263View Description Hide Description
Studies of the resistivity and Hall effect in n‐type (221) Si/(112̄2) Al2O3 films have shown that the electron mobility is a strong function of azimuthal direction in the plane of the film. Typical variations in mobility between high‐ and low‐mobility directions are approximately 40%. The anisotropy in mobility is explained on the basis of piezoresistance effects in Si, due to stresses induced by the differential thermal contraction between the Si and the Al2O3 substrate.
21(1972); http://dx.doi.org/10.1063/1.1654264View Description Hide Description
Epitaxialfilms of gadolinium‐gallium‐substituted yttriumirongarnet (Gd : Ga : YIG) films have been grown by rf‐sputtering techniques on 〈111〉 gadoliniumgalliumgarnet (GGG) substrates. The as‐deposited films were annealed to yield crack‐free epitaxialgarnets, which exhibited movable magnetic (bubble) domains. Typical magnetic data for the sputtered Gd : Ga : YIG films are presented.
21(1972); http://dx.doi.org/10.1063/1.1654265View Description Hide Description
Low‐loss waveguides for integrated optical devices are formed by electrically induced migration of ions in glass plates. The guiding region is located beneath the substrate glass. The transmission loss of the waveguides is estimated to be less than 0.1 dB/cm.
21(1972); http://dx.doi.org/10.1063/1.1654266View Description Hide Description
An investigation was made of the influence of an electric field on the transmission of a multilayered structure consisting of CdS and glass films. The same shift of the fundamental absorption edge was observed with the application of an electric field of 10–50 V to the sample as for a single crystal with a high applied voltage of about 1000 V. We also obtained a large‐modulation degree at longer wavelengths of 0.55–1.4 μ than at the wavelength of the fundamental absorption edge of CdS and obtained light‐intensity modulation of the He–Ne laser at 6328 Å.
21(1972); http://dx.doi.org/10.1063/1.1654267View Description Hide Description
A channeltron electron multiplier array has been used to detect exoelectron emission during the the fatigue cycling of aluminum. This provides the first two‐dimensional visual display of the onset and development of fatigue damage. Exoelectron emission is detected in less than 0.1% of the fatigue life and increases in intensity with continued fatigue cycling; final failure occurs in the region of most intense emission.
21(1972); http://dx.doi.org/10.1063/1.1654268View Description Hide Description
The effectiveness of a number of charge‐removal techniques during ion implantation into insulators has been examined by monitoring the ion‐induced characteristic x‐ray emission of target atoms during protonimplantation. Successful removal of charge buildup occurs for samples which are coated with a thin conductingsurface layer and for samples which have intimate contact between the implanted region and a conducting mask and are flooded with a defocused ion beam.
21(1972); http://dx.doi.org/10.1063/1.1654269View Description Hide Description
Ultrasonicsurface waves propagating on a piezoelectric substrate are accompanied by electric fields which can interact with charge carriers in an adjacent medium. This interaction and the resulting attenuation of the elastic surface wave have been measured for different metalfilms on a quartz single‐crystal substrate. As the films are deposited on the substrate, the resistivity of the films decreases continuously, and it was found that the interaction between the ultrasonic wave and the charge carriers in the film reaches a maximum for a resistivity of the films on the order of 5 MΩ/sq, but the magnitude of the resulting attenuation of the surface wave was dependent on the film material. Values of the maximum attenuation varied between 0.27 dB/cm for bismuth and 2.8 dB/cm for copper at a frequency of 31.5 MHz. A theoretical model was developed which showed good agreement with the experimental results for the materials used.
21(1972); http://dx.doi.org/10.1063/1.1654270View Description Hide Description
The distribution of fluorine ions implanted into gallium arsenide has been determined through the use of Auger electron spectroscopy combined with thin‐layer removal by argon ion sputtering. This technique is a chemical measure of the ion distribution and thus is not affected by the electrical properties of the implanted species. The leading edge and depth of the peak fluorine concentration are in fair agreement with the calculated LSS distribution; however, the trailing edge exhibits a tail which extends much deeper than expected. This tail is assumed to be due to damage‐enhanced diffusion.
21(1972); http://dx.doi.org/10.1063/1.1654271View Description Hide Description
GaAs samples were implanted with tellurium at room temperature or at 150 °C and annealed to 750 °C with an SiO2 or Si3N4 protective layer. The highest electron concentrations and brightest photoluminescence were obtained for the hot implants with a Si3N4 protective layer.