摘要:

Measurements of the thermoelectric properties of pure tungsten have been made between 1.2 and 7.0 K by a method in which the electric field within the metal was nulled by the simultaneous application of heat and electric currents. An unusual dependence of the thermoelectric properties on impurity concentration was observed below 3 K; these results are compared with conventional thermoelectric power measurements over the same range of temperatures.

ISSN:0003-6951    

DOI:10.1063/1.1654610

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Ruby‐laser‐induced intrinsic bulk damage in nine alkali‐halide crystals is reported. Within experimental error and for all of these crystals the damage field is greater than or equal to that measured at 1.06 &mgr;m and dc. The trend in breakdown fields among these crystals at 0.69 &mgr;m differs from that at longer wavelengths and suggests that, even though electron avalanche breakdown is the likely damage mechanism, the first signs of a frequency dependence to this process appear by 4.3×1014Hz.

ISSN:0003-6951    

DOI:10.1063/1.1654611

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Torque magnetometer measurements on epitaxial magnetic garnet films of nominal composition Y2.4Eu0.6Ga1.2Fe3.8O12have identified a growth‐induced noncubic magnetic anisotropy of 8000 erg/cm3which anneals away after several hours at 1300°C. Precision x‐ray measurements show that the film lattice constant changes by not more than 0.0003 Å during this annealing process. These results are similar to previous observations made on epitaxial films of other compositions but are contrary to earlier reports of Geisset al., Klokholmet al., and Cronemeyeret al.who had concluded that the noncubic anisotropy in Y&sngbnd;Eu films was exclusively stress induced and who reported large changes in film lattice constants with annealing.

ISSN:0003-6951    

DOI:10.1063/1.1654612

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Measurements of the impulse received by graphite and aluminum targets exposed to a 250‐psec laser pulse are reported. Experiments were conducted in air and vacuum at incident energies between 0 and 20 J. In both environments, there is a definite energy threshold, which is lower in air than in vacuum, below which no momentum is transferred. For a given energy above threshold, the impulse generated in air is greater than in vacuum.

ISSN:0003-6951    

DOI:10.1063/1.1654613

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Thick photographic emulsions are used with weakly absorbed radiations. These emulsions are capable of photographic densities much higher than 1.5. High‐density areas appear black, and photographic details are lost when viewed with transmitted light. Reflected‐light techniques can reveal those details. Application to x‐ray topography is demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.1654614

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Pulse amplification and energy extraction experiments in high‐pressure CO2amplifiers indicate that the effective rotational time constant for nanosecond energy extraction is an order of magnitude larger than the rotational relaxation time.

ISSN:0003-6951    

DOI:10.1063/1.1654615

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The effects of N2and O2atmospheres on arsenic diffusion in silicon from a doped oxide are studied by the backscattering method. The results indicate that the amounts of arsenic atoms diffused in silicon in a N2atmosphere are smaller than those in an O2atmosphere. This is caused by the differences in the properties of the silicon‐doped oxide interface during diffusion; the elemental arsenic is accumulated at the oxide side of the interface during diffusion in N2, whereas arsenic remains in the state of an arsenic oxide during diffusion in O2and is not accumulated.

ISSN:0003-6951    

DOI:10.1063/1.1654616

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A simple dynamic technique for the determination of the absolute signs of photoelastic coefficients is described. The method consists of comparing the known phase of a standing acoustic wave with the phase of the deflection of a photoelastically refracted laser beam, the waist of which is small compared with an acoustic wavelength. Experimental verification of the technique is presented along with specific limitations. The method forms a convenient complement to the Bragg diffraction measurement of the magnitudes of photoelastic coefficients.

ISSN:0003-6951    

DOI:10.1063/1.1654617

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Photocurrent measurements are shown to provide a convenient technique for determining the nitrogen concentration in the active region of GaP diodes designed for green light emission. The strength of the photocurrent peak at theA‐line energy can be correlated semiquantitatively with the diode efficiency in devices which differ only in their nitrogen content. Room‐temperature photocurrent measurements of Schottky barrier diodes formed by gold evaporation on epitaxial material can be similarly used for determining the relative nitrogen concentration.

ISSN:0003-6951    

DOI:10.1063/1.1654618

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Photoluminescence and scanning‐electron‐microscope measurements of minority‐carrier lifetime and luminescence efficiency have been made on Zn, N‐doped and Te, N‐doped GaP liquid‐phase‐epitaxy layers. Nitrogen concentrations are held constant at 1 × 1019cm−3, while the majority‐carrier concentrations were varied between 5 × 1016and 5 × 1018cm−3. It is shown that, for excitation levels equivalent to 10 A/cm2diode diffusion current density, a maximum external luminescence efficiency (in air) of 0.3&percent; is measured for ∼1018‐cm−3Zn, N‐doped GaP, in contrast to a maximum efficiency of 0.06&percent; for ∼1017‐cm−3Te, N‐doped GaP. These results suggest that significantly higher electroluminescent efficiencies approaching 0.3&percent; are available for diodes at 10 A/cm2, by increasing injection into ∼1018‐cm−3Zn, N‐doped GaP.

ISSN:0003-6951    

DOI:10.1063/1.1654619

出版商:AIP    

年代:1973

数据来源: AIP