Index of content:
Volume 14, Issue 7, 01 April 1969
EXPERIMENTAL CONFIRMATION OF SELF‐TRAPPING FROM THE DEPENDENCE OF SELF‐MODULATION ON PROPAGATION DISTANCE14(1969); http://dx.doi.org/10.1063/1.1652779View Description Hide Description
The self‐trapping interpretation of apparent small‐scale filaments has recently been questioned. Experiments were therefore undertaken to test whether the observed filamentary structure is caused by self‐trapping. We found that the filaments propagated over distances of the order of a few centimeters. To confirm this result, the spectral broadening in filaments versus propagation distance was determined. These observations give a nonlinear index change which agrees with the index change calculated from the observed diameter.
14(1969); http://dx.doi.org/10.1063/1.1652780View Description Hide Description
An experiment is described which confirms the theory of the distortion of a cholesteric structure by a magnetic field. Field effects in a sample of p‐azoxyanisole doped with cholesteryl acetate were viewed directly with a microscope, and the pitch of the helical structure was measured as a function of field strength.
14(1969); http://dx.doi.org/10.1063/1.1652781View Description Hide Description
The localization energy of excitons at N isoelectronic substituents in GaAs x P1−x has been determined from optical absorptionspectra for x ≲ 0.2. The results indicate that the binding energy of the N‐induced electron state associated with the X 1conduction band minima in GaAs may be relatively large, ∼0.08 eV. However, this state is still more than 0.3 eV above the lowest minimum at Γ1c . It is likely that there is no bound state associated directly with the Γ1conduction band minimum.
14(1969); http://dx.doi.org/10.1063/1.1652782View Description Hide Description
High‐frequency (MHz) and low‐frequency (kHz) current oscillations are found in photoexcited long GaAs diodes; the threshold field for the former is about 4.0 × 103 V/cm, and for the latter is about 1.5 × 103 V/cm. At an average applied field >4 × 103 V/cm, high‐frequency oscillation occurs first and continues for a while, then low‐frequency oscillation takes place. Experimental results suggest that the origin of high‐ and low‐frequency oscillation are different from each other; the former is the two‐valley transfer effect, and the latter the field‐dependent trapping effect.
14(1969); http://dx.doi.org/10.1063/1.1652783View Description Hide Description
Electron emission into vacuum has been observed from a forward‐biased Cs‐ and O‐treated GaAs p‐n junction. The device was operated at room temperature with dc bias voltage. The effective efficiency of the device (emission current divided by internal diode current eligible for emission) was 0.05%, while the over‐all efficiency of the device (emission current divided by total diode current) was 10−6. The low over‐all efficiency is explained in terms of sample geometry and surface activation.
14(1969); http://dx.doi.org/10.1063/1.1652784View Description Hide Description
Certain amorphous materials exhibit rapid electrical switching. The variation in their capacitance was evaluated as a function of temperature and electric field in the high‐resistance state. The zero‐field capacitance follows a Curie‐Weiss law above room temperature. At low temperatures, and at fields near the threshold of switching for higher temperatures, the open‐circuit incremental accapacitance becomes negative.
14(1969); http://dx.doi.org/10.1063/1.1652786View Description Hide Description
A high‐temperature aerodynamic molecular‐beam apparatus has been used to investigate the spatial distributions of argon atoms scattered from solid argon at 15°K for incident energies of 0.30 to 0.54 eV and incident angles of 0 to 70 deg. A highly nondiffuse flux of scattered atoms was observed for the noncondensing atoms.
14(1969); http://dx.doi.org/10.1063/1.1652787View Description Hide Description
Passive Q‐switching of a CO2 laser operating at 10.6 μ has been achieved with a mixture of sulfur hexafluoride and chlorotrifluoroethylene gases contained in a gas cell placed within the resonator. Use of chlorotrifluoroethylene gas to suppress spurious oscillations eliminates the need to use dispersive optical elements in the resonator.
ION IMPLANTATION DAMAGE OF SILICON AS OBSERVED BY OPTICAL REFLECTION SPECTROSCOPY IN THE 1 TO 6 eV REGION14(1969); http://dx.doi.org/10.1063/1.1652788View Description Hide Description
CHANGES OF OPTICAL REFLECTIVITY (1.8 TO 2.2 eV) INDUCED BY 40 ‐ keV ANTIMONY ION BOMBARDMENT OF SILICON14(1969); http://dx.doi.org/10.1063/1.1652789View Description Hide Description
We have measured the fractional change in the optical reflectivity of silicon in the 1.8–2.2 eV photon energy band as a function of 40‐keV antimony ion dose (1011–1015 Sb/cm2 at various implant temperatures (− 160–405°C). Approximate agreement is found between the change of reflectivity and previous measurements of lattice disorder as determined by backscattering of 1‐MeV He ions.
14(1969); http://dx.doi.org/10.1063/1.1652790View Description Hide Description
Isochronal annealing studies have been conducted on implanted boron and phosphorus layers in silicon. It is shown that the sheet conductance rise on annealing is dependent on the temperature at which the silicon is maintained during implantation. From the standpoint of conductance, low‐temperature implanting is to be favored.
14(1969); http://dx.doi.org/10.1063/1.1652791View Description Hide Description
Microwave techniques were used to measure the conductivity and dielectric constant of shock‐compressed Al2O3. At a pressure of 375 kbar, the dielectric constant increased and the conductivity remained negligible. From the dielectric constant, the molar polarizability was calculated and found to decrease.
14(1969); http://dx.doi.org/10.1063/1.1652792View Description Hide Description
The photoconductivity produced in some direct‐band‐gap semiconductors by the two‐photon absorption process is investigated theoretically and found to be a very complicated function of the crystal parameters, the excitation photonenergy, and the light excitation intensity. An application of the theory to a GaAs crystal is carried out.