摘要:

Superconducting tin bolometers are now reasonably well understood, and the results of calculations of performance are given over a large range of sheet resistances (0.01–1000 &OHgr;/□ at 4.2°K). Comparison of superconducting bolometers with semiconducting ones show that tin and germanium are equivalent in performance. The superconducting devices have the additional advantage of simplicity of sample preparation and lower impedance levels permitting higher operating speeds if desired.

ISSN:0021-8979    

DOI:10.1063/1.1659555

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Nuclear radiation is detected using a superconducting resonant circuit operated at 380 MHz. The technique uses a doped semiconductor crystal placed on the stub of a reentrant cavity. The cavity is lead plated and cooled to 4.2°K, such that it becomes superconducting. The cavity then becomes the frequency controlling element for a voltage variable oscillator. Nuclear radiation impinging on the crystal causes a change in the relative dielectric constant, which in turn causes the resonant frequency of the cavity to change. The crystal exhibits a peculiar trap property at 70°K or below, which allows any electron‐hole pairs generated in the crystal to be indefinitely trapped. The output frequency of the resonant circuit is then proportional to the total dose received by the crystal. Frequency shifts of the order of 4.051 kHz/min are observed in CdS, for a14C source of 1 &mgr; Ci.

ISSN:0021-8979    

DOI:10.1063/1.1659556

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A low‐temperature material‐properties analyzer, using a superconducting microwave resonant cavity, is discussed. Placing semiconductor or dielectric material samples in the cavity perturbs the resonant frequency, absorbed microwave power, and cavityQ. Additional perturbations occur when the sample complex dielectric constant is altered by a thermal, nuclear radiation, or optical stimulus. In samples such as Si, GaAs, CdS, and CdTe, these perturbations have been used to determine such material properties as relaxation time, lifetime, Fermi level, trap ionization energy, trap density, capture cross section, free‐carrier density, and trap population. A contactless experimental technique similar to the thermally stimulated conductivity experiment is proposed. The contactless ac measurement system is shown to be sensitive, accurate, useful with randomly shaped or powdered samples, and applicable to many types of insulators and semiconductors.

ISSN:0021-8979    

DOI:10.1063/1.1659557

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Coherent detection of applied radiation via a Josephson current step has been achieved with an applied frequency approximately a factor of 3 higher than heretofore reported. The detected signal is at 2.5 THz (118 &mgr;). The inadequacy of existing theory to predict the frequency dependence of the Josephson effect is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1659558

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Dayem‐bridge weak links have been fabricated by sputter etching niobium nitride thin films havingTc's of ∼15 K. These junctions exhibit a negative resistance region extending to 45 mV at 3.2 K, in which are seen self‐induced subharmonic current steps and structure near the energy gap voltage. Temperature dependence of these features and effects of applied microwave radiation are discussed, and possible explanations of the negative resistance region and of the self‐induced step structure are given.

ISSN:0021-8979    

DOI:10.1063/1.1659559

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Superconducting miniature microstrip resonators, operating atXband, have been constructed using vacuum‐deposited lead on low‐loss sintered alumina substrate. UnloadedQ's as high as 200 000 and 500 000 have been measured at 14.3 GHz at 4.2 and 1.8 K, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1659560

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The expression of an effective conductivity tensor for the magnetoacoustic amplification in extrinsic, nondegenerate semiconductors has been derived by the Boltzmann equation taking proper account of the Hall effect. This expression can be applied to any values of the frequency of acoustic waves and of the magnetic field in the classical regime. Detailed discussion of the Doppler‐shifted ultrasonic cyclotron resonance (DSUCR) is given by takingn‐InSb as an example. It is shown that the effective mass and the relaxation time of electrons can be determined by DSUCR. A brief discussion is also given on the magneto‐acoustoelectric instability inn‐InSb.

ISSN:0021-8979    

DOI:10.1063/1.1659561

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The phase shift with incident angle of reflected ultrasonic waves incident near the Rayleigh critical angle is reported. These measurements substantiate the predictions of our model. These predictions differ substantially from previous theories which neglect attenuation. For frequencies above 15 MHz the slope of the phase shift of an ultrasonic wave reflected from a water‐stainless steel boundary reverses at the Rayleigh critical angle. For frequencies below 15 MHz the phase shifts from 0° to +360°; above 15 MHz it shifts from 0° to +60° then to −60° and back to zero again on passing through the Rayleigh critical angle. The sensitivity of this phenomenon suggests that it could be useful in determining or evaluating changes in material properties such as cold work, residual stress, or grain sizes.

ISSN:0021-8979    

DOI:10.1063/1.1659562

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The lattice loss coefficient &agr;lfor acoustic waves in low‐resistivity (0.6 &OHgr; cm) CdS was determined from the electric‐field‐dependent incubation time. At the frequency of the maximum gain, the value for &agr;llies between the extrapolated experimental curves as measured by Bateman and McFee [J. Appl. Phys. 39, 4471 (1968)] and by Zucker, Zemon, and Wasko [Proc. Int. Conf. Phys. Semicond. 9th Moscow, 1968 2, 904 (1968)]. Two simple theories for the field dependence of the incubation time were compared and critically analyzed.

ISSN:0021-8979    

DOI:10.1063/1.1659566

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The kinetics of crystal growth of ferroelectric Rochelle salt have been studied by applying an electric field of 2–1000 V/cm between the upper face of a crystal and an electrode immersed in the water solution in contact with the lower part of the growing or dissolving crystal. It has been found that the rate of growth decreases while the rate of dissolution increases by about 10% above and belowTcof 24°C of the crystal at 900 V/cm. The results are discussed theoretically. Similar experiments under the application of a uniaxial pressure showed a less significant effect, while a vibrating alternating pressure of about 8 kg/cm2, and 50 cycles/sec showed a significant increase of the rate of growth by about 50%.

ISSN:0021-8979    

DOI:10.1063/1.1659567

出版商:AIP    

年代:1971

数据来源: AIP