Synthesis And High Pressure Study For ZnSe Nanorods

As a direct band gap semiconductor, ZnSe is potential ideal optical material for short-wavelength lasers and other photoelectronic devices. The quasi-one dimensional nanometer scale ZnSe, such as nanorod and nanowire, also have been attracted much interest because of its unique structure and luminescent properties at room temperature. The synthesis of ZnSe nanorod and their structural and physical properties, especially the photoluminescence property are still challenging topics in this field. High pressure can change the structure of materials, and thus change the physical properties. It provides us a very powerful tool to study the relations between the structure and physical properties. For ZnSe nanorods, there is no report on the structural phase transition and their photoluminescence properties in the field of high pressure. In this work, we have first systematically studied the synthesis of ZnSe nanorods by using hydrothermal method. DAC combination with synchrotron radiation energy-dispersive X-ray diffraction and Raman spectroscopy have been employed to study the structural phase transition of ZnSe nanorods under high pressure for the first time. The photoluminescence properties at ambient condition and hydrostatic pressure effect on the photoluminescence properties also have been studied. We have studied the factors that influence the structure and morphology of ZnSe product in the hydrothermal synthesis, including temperature, filling percentage and reactive temperature. The synthesis condition was optimized. ZnSe nanorods with about 70 nm in diameter and 500-1000 nm in length have been obtained at reactive temperature of 220 °C for 12h with 90% cubage filling in autoclave. The ZnSe nanorods have a pure Zinc-Blende (ZB) crystalline structure. We have carried out in situ high pressure measurements for the synchrotron radiation X-ray diffraction and Raman spectroscopy of ZnSe nanorods up to about 40GPa at room temperature. A phase transformation from ZB structure to Rock-salt structure has been observed at 8.0GPa, which is lower than that of bulk sample. A new diffraction peak appears in XRD pattern and a vibration peak disappears in Raman spectra at pressure of 4-5GPa,indicating a phase transition occurs from ZB to a tentative assigned structure of SC16. These phase transformations are reversible with a detention. The recovered compressed sample still keeps original nanoscale rod shape. We have studied the photoluminescence spectroscopy for as-grown ZnSe nanorods under ambient condition, and also for ZnSe nanorods treated under different hydrostatic high pressures. A photoluminescence band from 500 to 700 nm was observed in the photoluminescence spectrum of ZnSe nanorods at room temperature,...