Vibrating Properties Of One-dimensional ZnSe Nanowires And Nanobelts

One-dimensional nanomaterials have received extensive attention due to their special and excellent photoelectric properties and their potential applications in nano-optoelectronic devices. There are many factors such as structures, morphology, defects, lattice vibration etc that affect those properties. The lattice vibrations are closely related to the optoelectronic properties of one-dimensional nanomaterials. It impact a lot of physical properties of materials and the performance of devices. In addition, the lattice vibration is important foundation on studying of the macroscopic properties and microscopic processes of material. Raman scattering is an important tool of studying the vibrational performance of material, which provides lots of information about symmetry, composition, lattice dynamics, structural transitions, strain and electronic states of the studied system.In this thesis, the vibrational properties of ZnSe nanowires, nanobelts and Ge/GeSe heterostructure nanowires which are synthesized by one step thermal evaporation method are inveistigated by temperature-dependent Raman spectroscopy.The main contents are as follow:1. The research progress on the Raman spectroscopy of one-dimensional nanowires is reviewed in the chapter one.2. Fabrication of ZnSe nanowires by using one-step thermal evaporation of ZnSe powders. The vibrational properties of ZnSe nanowires are studied by using temperature-dependent Raman spectroscopy. Results shows both of TO and LO modes of ZnSe nanowires have a red-shift with elevating temperature. Some overtones and multi-phonon peaks only appear at high temperature. The intensity of overtones acoustics TA(L) elevates with increasing temperature while the surface mode disappears when temperature is higher than 296K.3. On the basis of the above work, ZnSe nanobelts were also synthesized by using one-step thermal evaporation of ZnSe powders. The quantitative relationship between Gruneisen parameters and vibrational modes is established and then the Gruneisen parameters was obtained. Finally, the thermal expansion coefficient of ZnSe nanobelts as a function of temperature is calculated.4. Ge/GeSe heterostructure nanowires are synthesized by one-step thermal evaporation of Ge and CdSe (or ZnSe) mixed powders. Dynamic behavior of phonons in Ge/GeSe heterostructure nanowires are studied by temperature-dependent Raman spectroscopy. The phonon behaviors are sensitive to temperature. The internal stress is calculated via XRD and Raman spectroscopy. The phonon confinement effect are also observed in Ge sub-nanowires.