Theoretical Studies On Raman Scattering In Several Low Dimensional Semiconductor System

With the rapid development of science and technology, the manufactureof the low dimensional semiconductor nanostructures and materials hasbecome true. Due to their strong quantum confinement of current carriers,nanostructures have plenty of optical phenomenon and effects, which arevery different from bulk materials. All kinds of quantum effects and freshcharacters of semiconductor nanostructures lead to not only themeaningful theoretical research, but also the valuable application indesigning and manufacturing various semiconductor photo-electric andmicroelectronic quantum devices in future.Raman spectrum, for its convenience and no damage to the materialsbeing measured, is a valid way to study semiconductor nanostructures.Raman scattering associated with phonons involves photo absorption andthe interaction between electron and phonon, and it has much to do withthe characters of electron intermediate states and phonon modes. Thus,through investigating frequency shift, line width, intensity andpolarization of Raman spectra, Raman scattering has become a stronginstrument to obtain the accurate information about electron and phononin low dimensional quantum systems. In this paper, Raman scattering infree-standing cylindrical quantum wires, quantum well-wires andspherical quantum dots is studied. This paper is constituted by fivechapters which are organized as follows.In the first chapter, a simple introduction to the theory of Ramanscattering and the current research of Raman scattering in low dimensionalsystems is given. The studying methods, the aims and the importance ofthis paper are discussed.Electron Raman scattering in free-standing cylindrical quantumwires and quantum well-wires is studied in the second chapter. Applyingsecond-order perturbation method in quantum mechanics and theapproximation of electron and hole effective masses, the expressions ofdifferential cross section are derived and the corresponding Ramanselection rules are given. The contribution to differential cross sectiondue to electron is compared to that due to hole. We find that thecontribution to differential cross section related to electron is farlarger than that related to hole, and it varies with differentsemiconductor materials, cylindrical radii and energies of incidentphotos.In the third chapter, one phonon Raman scattering in free-standingcylindrical quantum wires and quantum well-wires is studied. Accordingto dielectric continuum model, the approximation of electron effectivemass and third-order perturbation method in quantum mechanics, theexpression of differential cross section is derived. The Fr(o|¨)lich interaction is considered to illustrate the interaction between electronand hole. Raman selection rules are studied and the contribution todifferential cross section due to different Optical phonons is compared.The results are as follows: the contribution due to bulk longitudinaloptical phonon plays a main role in Raman scattering of quantum wire system,the contribution related to different optical phonon is different forvarious semiconductor materials, cylindrical radii and energies ofincident photos.Similar to the method used in the third chapter, one phonon Ramanscattering in spherical quantum dots is studied in the fourth chapter.For the strong quantum confinement, Raman spectra in spherical quantumdot show many singularities when the spherical radii change. Besides, thecontribution to differential cross section due to different opticalphonons differs from various energies of incident photos.In the last chapter, summary of the paper and the main results aregiven, the shortage and the further research of our paper are alsomentioned.