Research On The Synthesis And Photonics Properties Of Several One Dimensional Luminescent Semiconductor Nano-materials

In this dissertation, several one dimensional (1D) architecture nanostructures, such as:branched nano-heterostructures, doped micro-nanostructures, array nanostructures, were synthesized. The morphologies, component, structures of these as-grown nanostructures were characterized. Furthermore, we studied their photoluminescence/photonics systematically by UV-vis absorption PL spectrum,Raman spectrum,Scanning near-field optical microscope (SNOM) et.al. The main novel points are shown as follows:1. Based on two steps growth process and using ZnS nanowires as template, we synthesized several nanostructures, such as:ZnxCd1-xS-CdS branch nano-heterostructures,six-fold symmetrical CdS branch nano-homostructures,six-fold symmetrical ZnS-ZnO branch nano-heterostructures. Under different synthesis conditions, the chemical component of backbone ZnS nanowires can either maintained, or changed to ZnxCd1-xS alloy, and even to CdS completely. Therefore in such nano-heterostructures, except for the bandgap emission of branched CdS nanostructures in 504nm, these was another emission band that can be tunable between 337-504nm, which is come from the emission of backbone nanowires. The six-fold symmetrical ZnS-ZnO nano-heterostructures integrated the properties of ZnS and ZnO in them. Also, unique optical waveguide can be observed in six-fold symmetrical CdS nano-homostructures.2. Sn-CdS micro-nanostructures, Mn-ZnSe nanostructures, In-ZnTe nanostructures were synthesized by CVD technique. Strong defect state emission occurs in Sn doped CdS micro-nanostructures. Furthermore, these defect state emission were assisted by 1LO,2LO,4LO phonons, respectively, which demonstrated multi-phonon processes and nonlinear exciton (electron)-phonon coupling in these doped micro-nanostructures. The defect state emissions (multi-peaks) also dominate the PL spectra in doped ZnSe nanostructures. Whispering gallery modes cavity rather than F-P cavity might form in these nanostructures according to the mappings of each emission peaks. Under high excitation power of pulsed laser, bandgap state emission can achieve lasing because of its short cool time and fast radiative recombination process while defects state still hold the spontaneous emission due to its long cool time and slow radiative recombination process. The lasing mechanism is different from F-P cavity. There were different radiative recombination channels in the In-ZnTe nanostructures with different doped concentration. Therefore we can obtain green,red,near infrared emission in high purity ZnTe,doped ZnTe with 1.15%In (â…¢) concentration,doped ZnTe with 1.86%In (â…¢),respectively.3. According to the temperature profile of tube furnace, CdSxSe1-x alloy nanowires with different component were synthesized on single substrate wafer. Along the wafer, the emission wavelength of these alloy nanowires can be tuned from 498nm to 692nm. Furthermore, these nanowires can achieve lasing in the range of 503-692nm under high excitation power of pulsed laser. This is the first report about such large tunable wavelength in semiconductor nanowires laser. These integrated ternary alloy nanowires on chip may be used in red-green-blue display,white-light source,full-spectralcoverage solar cells.4.1D SnO2 nanobelts and nanowires were synthesized by evaporation method. The density of states of defect is larger in nanowires than that in nanobelts, which result in stronger strength of bound excitons than that in nanobelts. These nanostructures show bound exciton emission with different strength under fs pulsed laser excitation and produce lasing when the excitation power is high enough, while it only shows defect state emission under continuous-wave (CW) laser excitation. The lasing threshold of nanowires is lower than that of nanobelts because of its stronger bound exciton strength. Both exciton-phonon coupling and bound exciton result in the stimulated emission. Resonant Raman spectrum also indicate the strong exciton-phonon coupling and multi-phonons process in such SnO2 nanostructures.5. Several ZnO nanostructures, such as nanotetrapods,nanocombs,array nanostructures, were synthesized under different conditions by CVD. The morphologies and optical properties of ZnO nanostructures correlated with their synthesis conditions. Excellent emission properties occur in nanotetrapods and nanocombs, while the emission becomes a little worse in array nanostructures.