摘要:

The field‐emission current‐voltage behavior was examined for germanium crystals ranging from 0.001‐&OHgr;cmnto 0.0006‐&OHgr;cmptype, whose surfaces were prepared by high‐field evaporation. In contrast to the emission fromn‐type crystals from which linear Fowler‐Nordheim data were always obtained, the emission fromp‐type crystals produced nonlinear F‐N curves which were strongly influenced by temperature and illumination. This behavior was caused by the presence of a narrow, high‐resistance region near the emitting surface of thep‐type crystals. It is proposed that this depletion region was produced by surface inversion due to field penetration. Supporting evidence for this hypothesis was obtained from the spectral response and quantum efficiency of photoenhanced field emission and from measurements of the resistance and spatial profile of the depletion region. There was also evidence for carrier multiplication at high fields, leading to avalanche breakdown of the depletion region.

ISSN:0021-8979    

DOI:10.1063/1.1702953

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Hall measurements of GaP crystals grown by several different methods and doped with S, Te, Si, and Ge shown‐type behavior with donor concentrations ranging from 1016to 1019cm−3. Binding energies for the donor states at concentrations of 1018cm−3were estimated at 0.089±0.020 eV for S, 0.076±0.020 eV for Te, and 0.078±0.020 eV for Si. The electron mobility was usually between 60 and 100 cm2/V‐sec at room temperature and varied widely with temperature.

ISSN:0021-8979    

DOI:10.1063/1.1702954

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Through single‐crystal x‐ray diffraction methods, the crystal structure of TiNi has been determined in the temperature range −70° to 900°C. Contrary to what has been assumed from previous work based on the powder pattern methods, the TiNi crystal structure is not a simple CsCl type. Rather, it has ana0=9Å superlattice and ana0=3Å sublattice with 54 atoms per unit cell complex structure.The 9Å superlattice undergoes, at about 166°C, a ``martensitic'' pseudo order‐disorder transition which is not accompanied by a crystallographic transformation. Through the understanding of this unique transition the apparent contradicting observations made on TiNi by various past investigators can now be reconciled and the unusual physical properties associated with the alloy are explained qualitatively.

ISSN:0021-8979    

DOI:10.1063/1.1702955

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The results of torque measurements on thin nickel films were used to determine the saturation magnetization in the neighborhood of the Curie point. The films were deposited by evaporation in high vacuum (10−7to 10−8Torr) and protected with a silicon monoxide overcoat. The relative magnetization &sgr; was found to depend upon the temperature according to the power law &sgr;2=&xgr;(1−T/Tc) for temperatures near but below the Curie pointTc. Curie temperatures determined according to this power law were found to be considerably less than the Curie temperature of bulk nickel below 100Å. In addition, the parameter &xgr; was found to increase linearly with film thickness, from 20 to 225Å. Details are given on the techniques used for film preparation and for the magnetic measurements.

ISSN:0021-8979    

DOI:10.1063/1.1702956

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Arrays and networks of dislocations have been observed by diffraction contrast electron microscopy in crystals of natural milky quartz. These arrays and networks have been analyzed in terms of Burgers vectors suggested from examination of the crystal structure. The relevance of these dislocations to the plastic deformation of quartz is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702957

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Measurements of dislocation velocities in Ge crystals below 325°C are reported, at resolved shear stresses as high as 60kg/mm2. No drastic departures from known behavior at higher temperatures and lower stresses were observed. No statistically significant change in activation energy due to applied stress was detected, suggesting that dislocation motion under these conditions is probably limited by Peierls' forces.

ISSN:0021-8979    

DOI:10.1063/1.1702958

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

This paper describes experiments carried out to try to explain the degradation phenomenon of superconducting coils.It is established that flux jumps occurring in a low‐field zone cause a sudden decrease in the series current, which in turn causes a disturbance of field throughout the coil and thus probably results in a quench in a high‐field zone.Degradation of short samples is obtained by following a peculiar cycle of magnetization similar to that observed in a coil. An explanation is given to explain the difference of degradation observed between a short sample and a coil.A measurement of the apparent resistance of a superconducting wire under changing field conditions gives an equivalent resistivity of 10−14&OHgr;·cm fordB/dt= 200 G/sec.

ISSN:0021-8979    

DOI:10.1063/1.1702959

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Variations of the transition temperature and long‐range order parameter of Ta3Sn compacts were studied as functions of sintering time and temperature. Reacting the compacts for 4 days at 900°C produced a maximum in the order parameter (0.68) and the maximum transition temperature observed (8.35°K).Transition temperatures could be lowered to less than 4.2°K by vacuum heat treating presintered compacts at elevated temperatures.Ta3Sn was the only intermediate phase observed to form in the Ta‐Sn system between 700° and 1450°C.

ISSN:0021-8979    

DOI:10.1063/1.1702960

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Past experiments have shown that standing elastic waves can be excited in an yttrium iron garnet sphere through a parametric interaction with the magnetostatic modes. Lowest thresholds were obtained when the dc magnetic field was adjusted so that the difference between the microwave pump frequency and the acoustic frequency corresponded to the uniform precession frequency. The experiment reported in this paper utilizes a dielectric resonator to couple a high transverse rf magnetic field to the YIG sphere. This system enabled the observation of magnetoacoustic resonance using dc fields which are considerably lower than would be required to bias the idler frequency at the uniform precession. An explanation is offered which invokes a two‐step parametric process making use of Suhl's theory of the subsidiary absorption.

ISSN:0021-8979    

DOI:10.1063/1.1702961

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The energy spectrum of the beam of a four‐sector racetrack microtron has been measured here, using a high‐resolution double focusing beta‐ray spectrometer. For an energy gain per orbit of 750 keV, it was found that 50% of the integrated current in the eighth orbit (6 MeV) was contained in an energy interval of 34 keV and 90% of the beam current in a 73‐keV interval. This narrow energy spread (±0.3%) is of particular interest in the generation of submillimeter radiation and in the use of the microtron as an injector for high‐energy synchrotrons.

ISSN:0021-8979    

DOI:10.1063/1.1702962

出版商:AIP    

年代:1965

数据来源: AIP