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P. Murzyn C. R. Pidgeon P. J. Phillips J. -P. Wells N. T. Gordon T. Ashley J. H. Jefferson T. M. Burke J. Giess M. Merrick B. N. Murdin C. D. Maxey 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):220
We have made direct pump–probe measurements of spin lifetimes in long wavelength narrow-gap semiconductors at wavelengths between 4 and 10 μm and from 4 to 300 K. In particular, we measure remarkably long spin lifetimes, τs300 ps, even at 300 K for epilayers of degenerate n-type InSb. In this material the mobility is approximately constant between 77 and 300 K, and we find that τs is approximately constant in this temperature range. In order to determine the dominant spin relaxation mechanism we have investigated the temperature dependence of τs in non-degenerate lightly n-type Hg0.78Cd0.22Te of approximately the same band gap as InSb, and find that τs varies from 356 ps at 150 K to 24 ps at 300 K. Our results, both in magnitude and temperature dependence of τs, imply that the Elliott–Yafet model dominates in these materials. 相似文献
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B. N. Murdin 《Contemporary Physics》2013,54(2):391-406
Free-electron lasers based on radio-frequency linear accelerators provide an important source of far-infrared radiation which allow exciting experiments that cannot be performed in any other way. Facilities such as FELIX (Nieuwegein, The Netherlands), JFEL (Newport News VA, USA), FELBE (Dresden, Germany), CLIO (Paris, France) and others provide mid- and far-infrared output in picosecond pulses with micro-joules of energy. They give continuous, wide tuning in far-IR for resonant pumping of discrete transitions (with simultaneous coverage of mid-IR) from around 3 to 250 μm wavelength. This enables time-resolved spectroscopy, non-linear optics and spectroscopy of weak absorptions. They have been applied to a wide variety of problems in condensed matter physics, physical chemistry and biophysics. We review the physics applications of these sources. 相似文献
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Murdin BN Litvinenko K Clarke DG Pidgeon CR Murzyn P Phillips PJ Carder D Berden G Redlich B van der Meer AF Clowes S Harris JJ Cohen LF Ashley T Buckle L 《Physical review letters》2006,96(9):096603
We have used two-color time-resolved spectroscopy to measure the relaxation of electron spin polarizations in a bulk semiconductor. The circularly polarized pump beam induces a polarization either by direct excitation from the valence band, or by free-carrier (Drude) absorption when tuned to an energy below the band gap. We find that the spin relaxation time, measured with picosecond time resolution by resonant induced Faraday rotation in both cases, increases in the presence of photogenerated holes. In the case of the material chosen, n-InSb, the increase was from 14 to 38 ps. 相似文献
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B.N. Murdin 《Contemporary Physics》2013,54(2):116-117
Radar Astronomy is a new and growing branch of Astronomy. Although it seems that radio echo studies must be confined to the solar system, they can play an important part in developing our understanding of the Sun and the planets. At the present time these objects are barely detectable by radar techniques and much of the work has been concerned only with the moon. However it seems likely that within a decade we shall be able to measure the distances of the nearer planets and study their surfaces by this astronomical technique. This paper outlines what has already been achieved in the study of the moon and indicates some of the possible future results. 相似文献
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P. Blood E. D. Fletcher C. T. Foxon B. N. Murdin D. E. Lacklison 《Optical and Quantum Electronics》1991,23(7):S895-S900
The refractive indices of short-period binary (AlAs)m(GaAs)n superlattices, wherem = n, were investigated by measuring the beam divergences of optical waveguides using these superlattices as the core material. It is demonstrated that the refractive index depends on the period of the superlattice and not simply on the average composition. The refractive index is shown to depend in a systematic way on the direct bandgap of the superlattice, although the relationship may not be quite the same as that for a random alloy. 相似文献
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We have investigated the superconducting properties of the Bi1.7 Pb0.3Sr2Ca2−xCe
x
Cu3O10+δ system with x=0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found
to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate
decrease in the c-parameter with increased substitution of Ce at Ca site and volume fraction of high T
c (2 : 2 : 2 : 3) phase decreases and low T
c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition
temperature (onset) varies from 109 K to 51 K for x=0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent
state in this system; that is, Ca2+ → Ce4+ replacement changes the hole carrier concentration. Hole filling is the cause of lowering T
c of the system. 相似文献
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We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high
vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov
growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence
of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands
has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible
surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are
variations in the details of the island size distribution. 相似文献