tailieunhanh - Phonon characterization, structural and optical properties of Type-II CdSe/CdTe core/shell and Type-II/type-I CdSe/CdTe/ZnS core/shell/shell quantum dots

The CdSe, type-II CdSe/CdTe core/shell and type-II/type-I CdSe/CdTe/ZnS core/shell/shell quantum dots (QDs) were successfully synthesized in a noncoordinating solvent. The phonon characterizations, optical properties and structures of the synthesized QDs were characterized by Raman scattering (RS) spectra, photoluminescence (PL) spectroscopy, PL-decay lifetime, absorption spectroscopy (Abs), and X-ray diffraction (XRD). | VNU Journal of Science Mathematics Physics Vol. 36 No. 3 2020 47-57 Original Article Phonon Characterization Structural and Optical Properties of Type-II CdSe CdTe core shell and Type-II type-I CdSe CdTe ZnS core shell shell Quantum Dots Nguyen Xuan Ca Nguyen Thi Hien Faculty of Physics Thai Nguyen University of Sciences Tan Thinh Thai Nguyen Viet Nam Received 09 January 2020 Revised 17 February 2020 Accepted 05 April 2020 Abstract The CdSe type-II CdSe CdTe core shell and type-II type-I CdSe CdTe ZnS core shell shell quantum dots QDs were successfully synthesized in a noncoordinating solvent. The phonon characterizations optical properties and structures of the synthesized QDs were characterized by Raman scattering RS spectra photoluminescence PL spectroscopy PL-decay lifetime absorption spectroscopy Abs and X-ray diffraction XRD . The growth of QDs was monitored by using RS which demonstrated the formation of correct of the core shell and core shell shell structures. Observation results from XRD reveal that all QDs crystallize in the cubic phase with zinc-blende structure. The typical characteristics of spatially indirect recombination for type-II QDs were observed through Abs and PL spectroscopy. The ZnS shell significantly enhanced the PL quantum yeild QY the optical durability the chemical stability and separating CdSe CdTe QDs from the surroundings. The effect of excitation power on the PL properties of the CdSe core CdSe CdTe and CdSe CdTe ZnS QDs has been investigated. Keywords Quantum dot type-II type-I optical properties photoluminescence. 1. Introduction Colloidal semiconductors quantum dots QDs have been widely proposed to be used in applications such as light-emitting devices lasers photovoltaic and biomedical fluorescent labels because of the many desirable properties 1 2 . They have many advantages compared to organic fluorescence such as tunable emission wavelength multiplexing capabilities high-photoluminescence Corresponding author. Email address