Influence Of Phonon Confinement Research Articles

The influence of confined acoustic phonon on the quantum Peltier effect in doped semiconductor superlattice in the presence of electromagnetic wave

Based on the kinetic equation method, the quantum Peltier effect has been theoretically studied under the influence of confined acoustic phonon in doped semiconductor superlattice in the presence of the electromagnetic wave (laser radiation). There were complicated dependences of the analytical expression of the Peltier coefficient (PC) on quantities such as doped concentration of the superlattice, amplitude of the laser radiation, the cyclotron frequency of electrons and temperature of the system. In detailed consideration, the quantum number m was changed in order to characterize the influence of confined acoustic phonon. When setting the m to zero, we obtained the results that corresponded to the case of unconfined phonon. The theoretical results have been numerically evaluated and discussed for the GaAs:Si/GaAS:Be doped semiconductor superlattice (DSS). We found the oscillation of the PC according to enhancement of cyclotron frequency of electrons. Moreover, position of resonant peaks has shifted under the influence of phonon confinement. In the case of low doped concentration (n D), the PC decreased in non-linear way; then it reached a negative constant in high n D value. The non-linear change of the PC also has been detected when investigating its dependence on the laser amplitude. All numerical results have shown that the magnitude of the PC decreased due to the increase of phonon confinement effect. In short, the confinement of acoustic phonon caused the change of the quantum Peltier effect in DSS of GaAs:Si/GaAS:Be in quantitatively as well as qualitatively.

Influence of phonon confinement on the optically detected electrophonon resonance linewidth in parabolic quantum wells

We investigate the influence of optical phonon confinement described by Huang-Zhu (HZ) model on the optically detected electrophonon resonance (ODEPR) effect and ODEPR linewidth (ODEPRLW) in parabolic quantum wells (PQW) by using the operator projection. The obtained numerical result for the GaAs/AlAs parabolic quantum well shows that the ODEPR linewidths depend on the well's confinement frequency. Besides, in the two cases of confined and bulk phonons, the linewidth (LW) increases with the increase of confinement frequency. Furthermore, in the large range of the confinement frequency, the influence of phonon confinement plays an important role and cannot be neglected in considering the ODEPR linewidth.

Influence of phonon confinement on the optically detected electrophonon resonance linewidth in parabolic quantum wells

We investigate the influence of optical phonon confinement described by Huang-Zhu (HZ) model on the optically detected electrophonon resonance (ODEPR) effect and ODEPR linewidth (ODEPRLW) in parabolic quantum wells (PQW) by using the operator projection. The obtained numerical result for the GaAs/AlAs parabolic quantum well shows that the ODEPR linewidths depend on the well's confinement frequency. Besides, in the two cases of confined and bulk phonons, the linewidth (LW) increases with the increase of confinement frequency. Furthermore, in the large range of the confinement frequency, the influence of phonon confinement plays an important role and cannot be neglected in considering the ODEPR linewidth.

Optically detected electrophonon resonance in quantum wells via two-photon absorption processes under the influence of phonon confinement

The multi-photon (nonlinear) optical absorption power by electrons in square quantum wells, taking account the electron-confined optical phonon interaction, is calculated using the state-dependent projection technique. We numerically obtain the dependence of the absorption power on the photon energy in the GaAs/AlAs semiconductor quantum well. By analysing this dependence, we show clearly the transition corresponding to each resonant peak, including the optically detected electrophonon resonance (ODEPR). Also, using a computational method, we obtain the line-width of the ODEPR as profiles of the curves. The dependence of the ODEPR line-width on the width of the quantum well shows that the ODEPR line-width for two-photon absorption is about one order of value smaller than it is for one-photon absorption.

Influence of phonon confinement on the optically detected electron-phonon resonance linewidth in quantum wells

We investigate the influence of phonon confinement on the optically detected electrophonon resonance (ODEPR) effect and ODEPR line-width in quantum wells. The obtained numerical result for the GaAs/AlAs quantum well shows that the ODEPR line-widths depend on the well's width and temperature. Besides, in the two cases of confined and bulk phonons, the linewidth (LW) decreases with the increase of well's width and increases with the increase of temperature. Furthermore, in the small range of the well's width, the influence of phonon confinement plays an important role and cannot be neglected in considering the ODEPR line-width.

Influence of phonon confinement on the optically detected magneto-phonon resonance line-width in quantum wells

We investigate the influence of phonon confinement on the optically detected magneto-phonon resonance (ODMPR) effect and ODMPR line-width in quantum wells. The ODMPR conditions as functions of the well's width and the photon energy are also obtained. The shifts of ODMPR peaks caused by the confined phonon are discussed. The numerical result for the GaAs/AlAs quantum well shows that in the two cases of confined and bulk phonons, the line-width (LW) decreases with increasing well's width and increases with increasing temperature. Furthermore, in the small range of the well's width, the influence of phonon confinement plays an important role and cannot be neglected in reaching the ODMPR line-width.

Optical phonons in nanostructured thin films composed by zincblende zinc selenide quantum dots in strong size-quantization regime: Competition between phonon confinement and strain-related effects

Raman scattering in combination with optical spectroscopy and structural studies by X-ray diffraction was employed to investigate the phonon confinement and strain-induced effects in 3D assemblies of variable-size zincblende ZnSe quantum dots close packed in thin film form. Nanostructured thin films were synthesized by colloidal chemical approach, while tuning of the nanocrystal size was enabled by post-deposition thermal annealing treatment. In-depth insights into the factors governing the observed trends of the position and half-width of the 1LO band as a function of the average QD size were gained. The overall shifts in the position of 1LO band were found to result from an intricate compromise between the influence of phonon confinement and lattice strain-induced effects. Both contributions were quantitatively and exactly modeled. Accurate assignments of the bands due to surface optical (SO) modes as well as of the theoretically forbidden transverse optical (TO) modes were provided, on the basis of reliable physical models (such as the dielectric continuum model of Ruppin and Englman). The size-dependence of the ratio of intensities of the TO and LO modes was studied and discussed as well. Relaxation time characterizing the phonon decay processes in as-deposited samples was found to be approximately 0.38ps, while upon post-deposition annealing already at 200°C it increases to about 0.50ps. Both of these values are, however, significantly smaller than those characteristic for a macrocrystalline ZnSe sample.

Geometry dependence of the phonon modes in CdSe nanorods

We investigated the geometry dependence of the first-order Raman scattering band of CdSenanorods experimentally. The band has an asymmetric shape and its position andexact line shape depend on the nanorod diameter and aspect ratio. The bandconsists of contributions from the longitudinal optical phonon and surface opticalphonon modes. While the position of the longitudinal optical phonon related bandis purely diameter dependent, the position of the surface optical phonon banddepends on the nanorod’s aspect ratio. This can be explained by the influenceof phonon confinement and a model for surface optical phonons in nanorods.