Volume 13, Issue 6, 15 September 1968
Index of content:
13(1968); http://dx.doi.org/10.1063/1.1652568View Description Hide Description
Increasing the discharge current through a small dc‐excited 6328‐Å laser changes the index of refraction of the discharge and causes a blue shift of the laser oscillation frequency of ∼1 MHz/mA. The shift is independent of laser cavity tuning and decreases with increasing dc discharge current. Approximate calculations plus other experiments indicate that this shift represents the dispersive effects of the strong 6334‐Å and 6402‐Å upward transitions from the neon 1s 5 metastable level. The residual spectral width and FM noise in stable 6328‐Å lasers, especially as compared to 1.15‐μ lasers, may be due to plasma disturbances acting through this dispersive mechanism, rather than to microphonic disturbances as commonly suggested.
13(1968); http://dx.doi.org/10.1063/1.1652569View Description Hide Description
The electrical behavior of 20–50‐keV Bi implanted layers in silicon has been evaluated using Hall effect and sheet resistivity measurements. Implants of greater than 1014/cm2 performed at room temperature show a large increase in the number of carriers/cm2 for short anneals at ≈600°C that is associated with the reordering of the lattice. Although Rutherford scattering measurements (performed at Chalk River Nuclear Laboratories) indicate that ≈80% of the Bi atoms are substitutional, only ≈20% are effective electrically. The peak value of the carrier density distribution is ten times the corresponding maximum solid solubility.
13(1968); http://dx.doi.org/10.1063/1.1652570View Description Hide Description
Laser‐produced sparks in air, butane, and helium at atmospheric pressure have been studied in a 200‐kG magnetic field. The influence of the magnetic field on the breakdown threshold, on the visible radiation emitted by the plasma, and on the plasma expansion has been investigated.
CRITICAL CURRENT DENSITIES IN SUPERCONDUCTING NIOBIUM FILMS SPUTTERED REACTIVELY IN THE PRESENCE OF NITROGEN GAS13(1968); http://dx.doi.org/10.1063/1.1652571View Description Hide Description
A critical current density of about 2 × 105 A/cm2 in a transverse external field of 73 kOe, parallel to the film plane, was obtained at liquid‐helium temperature for niobiumfilmsdeposited on glass substrates by sputtering technique in an argon atmosphere with a dilute addition of nitrogen. This critical current density is larger than any other reported values for refractory metal carbides and nitrides with the NaCl structure.
13(1968); http://dx.doi.org/10.1063/1.1652572View Description Hide Description
A discrepancy has been observed between the experimental behavior of electrical resistivity and temperature coefficient of resistivity as a function of film thickness in thin single‐crystal silverfilms when compared with geometrical size effect theory. The discrepancy has been attributed to the observed change in the microstructure of the films as shown by the transmission electron microscopy study and to the effect of lattice as well as electron energy quantization on electrical conduction. The study calls for an exact calculation of the role of quantization in structurally perfect thin films.
13(1968); http://dx.doi.org/10.1063/1.1652573View Description Hide Description
In the nucleation theory for water condensation, we argue that the surface tension of an embryonic droplet of water molecules is more nearly approximated by the surface tension of ice than that of liquid water, and this resolves the discrepancy between the Lothe‐Pound nucleation theory and experimental observation.
ELECTROLUMINESCENCE OF RARE‐EARTH AND TRANSITION METAL MOLECULES IN II‐VI COMPOUNDS VIA IMPACT EXCITATION13(1968); http://dx.doi.org/10.1063/1.1652574View Description Hide Description
It is shown experimentally that it is possible to excite rare‐earth and transition metal ions included in a II‐VI compound matrix as fluoride molecules by direct, hot‐electron impact. Electron‐hole pairs in the matrix are unnecessary and even undesirable. AC excitation of a thin film structure has given external power conversion efficiency of about 10−4 at several optical frequencies including the 5480‐Å line of Tb3+.
13(1968); http://dx.doi.org/10.1063/1.1652576View Description Hide Description
The sensitivity and versatility of a phonondetector based on the optical detection of the spin population difference of an impurity ion through the spin‐phonon interaction is demonstrated. Phononsgenerated at 1.4°K by a variety of transducers using at most several milliwatts of rf power at 9.5 GHz were detected.Phononsgenerated at the 2nd and 3rd harmonics were also detected.
13(1968); http://dx.doi.org/10.1063/1.1652577View Description Hide Description
Germanium and silicon monocrystals with controlled grown‐in medium‐angle grain boundaries and crystals with isolated dislocations are subjected to a scanning electron beam (SEB) with simultaneous application of a bias field in a transversal direction. Amplification of the induced current signals and oscillographic display reveals clearly the extended space charge of defects and the junction behavior of a two‐dimensional array of edge dislocations with a radius of the space‐charge pipe from a few microns to 25 microns.
13(1968); http://dx.doi.org/10.1063/1.1652578View Description Hide Description
A quantum theory of magnetoacoustic amplification in semiconductors is given. Calculations for InSb show that the quantum theory can explain both branches of the acoustoelectric current oscillations observed by Kikuchi1 and Kino.2 For high electron drift velocities the gain shows a resonant behavior when the Doppler‐shifted acoustic frequency is equal to a multiple of the Larmor frequency.