摘要:

Measurements of resistance (dV/dI) versus bias (V) have been made for Al&sngbnd;I&sngbnd;Bi junctions at 77°K up to pressures of 30 kbar. The junctions were prepared by evaporation upon freshly cleaved mica and the pressures generated in a girdle die using AgCl as the pressure transmitting medium. The results are reversible with pressure cycling. A conduction maximum occurs at ≈0.13 V and a kink at ≈−0.15 V. The maximum changes with pressure at a ratedV/dP=−1.7×10−6V/bar. A change in the tunneling curve is observed at the semimetal to semiconductor transition.

ISSN:0021-8979    

DOI:10.1063/1.1658044

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The internal friction of several compositions of V2O5·P2O5glasses has been measured in the kHz region from 100° to 400°K. A relaxation peak strongly dependent upon composition exists below room temperature in these glasses. The activation energies of the peaks lie between 0.1 and 0.2 eV. The isotropic elastic moduli and densities were measured for some compositions. These glasses aren‐type semiconductors. Direct current electrical conductivities ranged from 6×10−2to 4×10−6&OHgr;·cm−1at 100°C over the composition region studied. The connection between the internal friction and the dc electrical conductivity is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1658045

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Transient recombination lifetimes have been measured in high‐purity,n‐type, float‐zone silicon from 4.2°K to room temperature. Photoconductivity decay curves and quiescent electrical conductivity values have been obtained by a microwave reflection technique which does not require electrical contacts to the sample. Experiments were performed at low injection levels on unirradiated samples and after irradiation with 30‐MeV electrons. An unusual feature of the data is a pronounced increase in lifetime with decreasing temperature below 45°K, similar to a trapping effect. This variation of lifetime with temperature has been explained using the two‐lifetime transient analyses of Sandiford and Wertheim. The temperature dependences of the capture cross sections are calculated and compared with the theoretical predictions of Lax and with other experimental results.

ISSN:0021-8979    

DOI:10.1063/1.1658046

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The rheological behavior of a brittle, strain‐rate sensitive, polycrystalline, organic solid explosive (pressed TNT) was investigated under conditions of uniaxial compressive strain. The wave structure of shocks introduced into the specimen material was determined by examining quartz stress transducer records. An ``elastic precursor'' wave forms in the specimen if the driving stress is below approximately 10 kbar. The length, shape, magnitude, risetime, and velocity of the precursor wave and the risetime of the follower wave are functions of both the specimen thickness and driving stress. Stress‐strain‐variable‐strain‐rate curves and corresponding Hugoniot curves were experimentally determined for two specimen thicknesses. All sets of curves were found to be related to specimen thickness. Shock hydrostats were estimated at the lower strain levels from those stress‐strain‐constant‐strain‐rate curves most closely in agreement with the Hugoniots. A simple elastic‐plastic theory that incorporated the results from an associated uniaxial stress study was used to determine the deviatoric stress component. The isentropic and isothermal hydrostats were deduced from the shock hydrostats; the isothermal curves were compared with experimentally obtained results. A numerical study indicated that transducer data were not significantly affected by wave reflections and interactions. Also verified was the adequacy of the simple elastic‐plastic model used to describe the loading response.

ISSN:0021-8979    

DOI:10.1063/1.1658047

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Final yield strengths of metals plastically deformed in one‐dimensional strain by shock compression are calculated from the theory of shock propagation and work hardening. An energy analysis of the shock‐relief cycle employs a Mie‐Gru¨neisen‐type equation of state and appropriate Hugoniot compressibility curve to determine the thermodynamic states of the material and the plastic work done. The residual elastic strain energy stored in the metal was estimated assuming that a portion of the plastic work remains in the form of lattice defects. Results for copper and nickel are found to be in reasonable agreement with experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1658048

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Germanium and Mg3Sb2were vapor codeposited on a low‐temperature substrate. The resulting films were amorphous. Subsequent heating to temperatures above room temperature resulted in an ultrafine‐grained structure. Conductance measurements, used to follow the annealing process, indicated two distinct annealing modes. At low temperatures, the conductance decreased on annealing. Somewhat above room temperature, a sudden, almost discontinuous, increase in conductance occurred over a very narrow transition temperature interval. Annealing above this temperature resulted in a gradual increase in conductance. Electron microscope studies indicate that the annealing behavior above the transition temperature interval is associated with extensive grain growth, though below it no structure is observable at all. A study of the annealing behavior below the transition temperature interval by means of conduction measurements indicates an activation energy, for what must be a structural change, of about 0.1 eV. An ordinary diffusion process requires an activation energy an order of magnitude higher. A new mechanism is suggested to account for these observations.

ISSN:0021-8979    

DOI:10.1063/1.1658049

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Amorphous bismuth‐tellurium oxide films have been prepared over a wide composition range by means of multicathodic reactive sputtering. Optical properties of the mixed‐oxide films are not algebraic combinations of the optical properties of the single‐oxide films. Relatively large quantities of bismuth oxide can be incorporated in virtually colorless mixed‐oxide films, because the bismuth oxide undergoes an unidentified transformation. In the high atomic ratio (Bi/Te) region, optical absorption is visible and attributed to the formation of the impurity‐stabilized &dgr;‐Bi2O3structure.

ISSN:0021-8979    

DOI:10.1063/1.1658050

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An experimental investigation has been made of the nucleation of Ag on single‐crystal MoS2for deposition rates in the range 8×1011−7×1013atoms/cm2·sec and at two substrate temperatures, 30 and 200°C. At the lower deposition rates employed, the Ag deposits were found to be very highly oriented with Ag (111) parallel to MoS2(0001) and Ag [11¯0] parallel to MoS2[21¯1¯0]. The smallest Ag clusters detected by transmission electron microscopy were approximately 20 Å in diameter. Nucleation rates were determined for various deposition rates and it was found that the nucleation rate varied linearly with the deposition rate at each temperature. Attempts were made to fit both the capillarity and atomistic theories of thin‐film nucleation to the experimental results, and it was found that neither theory could be fitted in a completely consistent manner. Explanations for the differences between theory and experiment are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1658051

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1658052

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1658053

出版商:AIP    

年代:1969

数据来源: AIP