Preparation And Optical Properties Of Semiconductor Nanocrystals

Nowadays, Due to the excellent physical and chemical properties of the nanoscale semiconductor, such as luminousity, nonlinearoptical property and quantum effect, the synthesis and the properties of semiconductor nanocrystals have been extensively investigated from pure basic research to the application of these nanomaterials in photoelectric, electrical, and biologic devices. This paper focus on the CdS nanocrystals and Cd1-xMnxS(x=0.1,0.2) nanocrystals were successfully synthesized by a mechanical alloying process, ZnSe nanocrystals was synthesized by a simple colloidal solution way. The main contents are as follows:1. CdS nanocrystals have been successfully synthesized by a mechanical alloying process. The X-ray diffraction (XRD) pattern shows that the major phase of the product was wurtzite CdS compound after mechanical alloying of the elemental powders for 60 min. All the diffraction peaks from the elemental Cd and S powders disappeared completely in the XRD patterns of as-milled CdS nanocrystals ball milled for more than 10 h. High-resolution transmission electron microscopy (HRTEM) images confirmed the wurtzite structure of asmilled CdS nanocrystals. The as-milled CdS nanocrystals were subsequently capped with trioctylphosphine oxide/trioctylphosphine/nitric acid (TOPO/TOP/NA), which leads to the formation of yellow dispersion solution.The size of capped CdS nanocrystals ranges from 1.6 to 6.2 nm. The capped CdS nanocrystals show similar optical properties to those CdS nanocrystals prepared by the wet chemical process, the absorption peaks for the capped CdS nanocrystals locate within the range of 345 to 380 nm.2. Cd1-xMnxS nanocrystals have been successfully synthesized by a mechanical alloying process. XRD patterns shows the as-prepared Cd1-xMnxS was wurtzite. Due to dopping the Mn ion, the crystal lattice of Cd1-xMnxS was a little different to the standard CdS nanocrystals, The as-milled CdS nanocrystals were subsequently capped with trioctylphosphine oxide/trioctylphosphine/nitric acid (TOPO/TOP/NA), which leads to the formation of yellow dispersion solution. Absorption edge of Cd1-xMnxS(x=0.1,0.2) ball milled for 10 h locate at about 360nm. With increasing the content of Mn ion, the band gap of product become bigger.3. ZnSe nanocrystals have been successfully synthesized by this simple way. HR-TEM images confirmed that ZnSe nanocrystals were cubic structure. The as-prepared ZnSe nanocrystals were measured by UV-visible test. The samples show that absorption peak from 324nm to 362nm. The samples were subsequently measured by PL test. ZnSe nanocrystals producing PL in a blue region. The samples PL peaking from 365nm to 437nm.