声学形变势表面极化子中的平均声子数

利用线性组合算符方法，计算了声学形变势表面极化子中的平均声子数，结果表明，光学声子平均数（Na）和声学声子平均数（Nb）均是电子运动速度和电子距离晶体表面的深度的函数。对AgCl晶体进行数值计算，结果表明：Na和Nb均随深度Z的增加而减少；Na随振动频率λ的增加而选减后增；Nb随η的增加而减少；并且，对慢速运动的电子，电子运动速度对Na、Nb的影响可以忽略。     

Lattice vibration spectra of AII(1−x)BII(x)CVI systems

Phonon spectra for mixed systems of II–VI compounds are worked out in an MRI model and the Debye Waller factor evaluated from these phonons are compared with the recent experimental values of Baudouret al where some interesting behaviours are reported.     

Study of optical phonon modes of CdS nanoparticles using Raman spectroscopy

The reduction in the grain size to nanometer range can bring about radical changes in almost all of the properties of semiconductors. CdS nanoparticles have attracted considerable scientific interest because they exhibit strongly size-dependent optical and electrical properties. In the case of nanostructured materials, confinement of optical phonons can produce noticeable changes in their vibrational spectra compared to those of bulk crystals. In this paper we report the study of optical phonon modes of nanoparticles of CdS using Raman spectroscopy. Nanoparticle sample for the present study was synthesized through chemical precipitation technique. The CdS nanoparticles were then subjected to heat treatment at low temperature (150°C) for extended time intervals. The crystal structure and grain size of the samples were determined using X-ray diffraction and HRTEM. The Raman spectra of the as-prepared and heat treated samples were recorded using conventional Raman and micro-Raman techniques. The spectrum of as prepared sample exhibited an intense, broad peak at 301 cm⁻¹ corresponding to the LO phonon mode. Higher order phonon modes were also observed in the spectra. A noticeable asymmetry in the Raman line shape indicated the effect of phonon confinement. Other features in the spectra are discussed in detail.     

Interface Phonons and Polaron Effect in Quantum Wires

The theory of large radius polaron in the quantum wire is developed. The interaction of charge particles with interface optical phonons as well as with optical phonons localized in the quantum wire is taken into account. The interface phonon contribution is shown to be dominant for narrow quantum wires. The wave functions and polaron binding energy are found. It is determined that polaron binding energy depends on the electron mass inside the wire and on the polarization properties of the barrier material.     

Phonon sattering by nutral donors in n-type silicon

The scattering of phonons by neutral n-type impurities in silicon is studied. Following Keyes, who determined the phonon relaxation time for scattering by neutral impurities in n-type germanium, the relaxation time for the silicon band structure is developed. This scattering comes about due to the large effect of strain on the hydrogen-like donor ground-state energy level. The change in energy of the ground state due to the strain caused by phonons is calculated and the resulting phonon scattering relaxation rate is derived.     

Measurement and Prediction of the Dynamic Temperature Distributions in Soda-Lime Glass Plates

Experimental measurement of the dynamic internal temperature distribution in soda-lime glass plates using thermocouples fused in the glass has been carried out. Experimentally measured temperatures are compared to predictions obtained from the solution of the transient energy equation where the internal radiative transfer has been accounted for using rigorous radiative transfer theory. A discussion of the experimental method, the process used to fuse the thermocouples in the test plates and the rigorous formulation of the energy equation, for semitransparent materials is given. Predicted and measured instantaneous surface temperatures are compared and very good agreement is obtained. It is also concluded that the empriical equation for the phonon conductivity used in the analysis underpredicts the conductivity. A 20% increase in phonon conductivity is shown to significantly improve the agreement between measured and predicted centerline to surface temperature differences.     

Infrared reflectivity studies of gax in1-x asy p1-y quaternary compounds

Reflectivity spectra have been measured on Ga_xIn_1-xAS_yP_1-y quaternary alloys, lattice-matched to InP substrates, covering the complete composition range from y = 0 (InP) to y = 1 (Ga_0.47 In_0.53 As). The spectra have been analysed to obtain parameters of both the free carriers and lattice vibrations. The reflectivity method has been used to measure the carrier density and mobility, the relatively low mobilities obtained confirming the electrical measurements explained previously by the presence of strong alloy scattering in this system. Four phonon modes, corresponding to InAs-, GaAs-, InP- and GaP-like vibrations, were observed over most of the composition range, except for y ≲ 0.25 where the GaAs mode was not observed and the GaP mode was a weak mode within the reststrahlen band of the InP mode. Thus the behaviour of the system may be termed "two"-four mode. The oscillator strengths of the four modes are consistent with this behaviour and their variation may be explainable by assuming that Ga_xIn_1-xAS_yP_1-y is a random alloy.     

Phononic and spin excitations in Y1?xPrxBa2Cu3O6.9 crystals

The Y_1–x Pr _x Ba₂Cu₃O_6.9 system has been investigated by quantitative-Raman measurements. The magnetic response of the antiferromagnetic ordered Cu spins in the CuO₂ plane has been observed via the two-magnon-Raman scattering. The in-plane exchange energy is determined to 780 cm^–1 in the system withx=1. Phonon behavior as well as magnetic scattering indicate that the band structure of the CuO₂ planes in PrBa₂Cu₃O_6.9 is similar to that in insulating YBa₂Cu₃O₆.     

The effect of quasiparticle self-generation on the performance of small gap multiple tunnelling STJs

Due to the slowness of the electron–phonon interaction in small gap STJs currently being developed as the latest generation of photon detectors, during the device operation a broad statistical distribution of interacting quasiparticles and phonons is established. This gives rise to new physical phenomena and also renders the traditional Rothwarf–Taylor model completely inadequate for the analysis of quasiparticle and phonon dynamics for all traditional superconductors except unproximised Nb. We have developed a new kinetic approach replacing the Rothwarf–Taylor scheme. We demonstrate the results of experimental and theoretical studies of the new physical phenomenon of quasiparticle self-generation in a heavily proximised multiple tunneling Ta/Al STJ and discuss the implications of the observed quasiparticle self-generation for photon detection.