Optical And Electronic Properties Of An Individual Multi-branched CdS Comblike Micro/Nanostructure

Cadmium sulfide (CdS) nanostructure has gradually been evolved from simplyone-dimensional structure to complicated branched-structures, such as comb-like arraystructures, through the fine control of synthesis conditions. The CdS nanostructure withordered and controllable branches is a natural nanowire array, which is very suitable tobuild up more powerful devices with extend complexity and higher dimension. While theperformance of the device mainly depend on the optical and electrical properties of thebranched nanostructures. However, there are only few studies on optical and electricalproperties of individual CdS branched array structure were reported. Therefore, the thesismainly focus on the detail analysis of optical and electronic properties from a singlecomblike structure.To utilize temperature dependent photoluminescence (PL) and Raman spectra,time-resolved PL, Raman mapping, the optical and electrical properties, field emissionbehavior and transport characteristics of carriers on a multi-branched CdS comblike arrayswere obtained. These works will contribute to build up more complicated and powerfuldevices based on branched CdS comblike array nanostructure. The detail studies are listedas follows:(1) The branched CdS comblike arrays were synthesized by in situ chemical vapordeposition (CVD). Through characterizing the structure and doping concentration by SEM,TEM and EDS, the growth mechanism of the CdS comblike microstructures has beenproven by the intermediate synthesis product during the growth process.(2) Temperature-dependent Raman and photoluminescence spectra of different parts ofan individual Sn-doped CdS comb-like nanostructure reveal that the strongerelectron-phonon coupling exist in trunk-branch junction, which is further confirmed by theHuang-Ryns factor. The higher Sn doping concentration and localized deformation in thejuncion part is the main reason to induce strong electron-phonon coupling at the localjunction, which is consistent with the STEM and EDS analysis. In addition, the laserdamage threshold of junction is significantly increased when the temperature increase andthe qualitative analysis of light propagation shows that a relative low loss coefficient in aCdS comb-like nanostructure, which decrease with the excitation power increase.(3) The field-emission properties of individual CdS comblike nanostructures withsmooth end facet and needle-shaped tips were studied respectively. The CdS comb-like nanowires with needle tips show tremendous emission current density, which have apotential to be used as field emission electron source with cantilever structure. The smallereffective emission area and bigger field enhancement factor lead to tremendous emissioncurrent density.(4) The electron transport properties of the comb-like CdS nanostructure were studiedthrough the I-V test, The resistivity of the wire is about50Ω cm. There is no additionalimpedance for the complicated multi-branched array structure, which have greatsignificance to construct multichanel micro circuit based on the branched microstructures.