Device Fabrication And Photoelectric Properties Of Low Dimensional CdS Nanostructures

Recently,as the rapid development of silicon based devices makes the integration much higher,and the critical dimension is also shrinking.But with physical limitations to further transistor scaling being reached,that is not the only challenge for more powerful and smaller electronic devices to be achieved.Engineering at very small scales will produce technologies that utilize materials with new and fundamentally unique properties.One-dimensional nanomaterials such as semiconductor nanowires,nanoribbons are being developed as blocks for high performance electronic and photonic devices.As an important II-VI semiconductor material,CdS has direct band gap of 2.4 eV at room temperature and thus is seem to be a possible for optoelectric applications in the visible spectrum range.The thesis focuses on the fabrication and properties of the electronic transport properties of field effect transistor(FET)based on the single CdS nanobelts,and the study of a simple method that combined with photolithography technology to in situ investigate the photoluminescence of Au NPs decorated 3D hierarchical branch CdS nanostructures.(1)The fabrication of low dimensional CdS nanostructers.The low dimensional CdS nanostructers were synthesized on Si substrate utilizing a simple and feasible chemical vapor deposition(CVD)method.The nanostructure with different morphology was obtained by controlling the growth temperature,growth pressure and soaking time.The nanowire,nanobelt and three dimensional Cd S nanostructures were fabricated in the thesis.(2)Properties of CdS nanobelts FET modified by Sulfide ion implantation.CdS nanoblets has been modified with S doping by ion implantation to modulate the photoelectric properties.The structure and photoelectric properties of samples were analyzed by X-ray diffraction(XRD),photoluminescence(PL)and Raman spectra.The PL emission of CdS nanoblets shows two peaks at 518 and 730 nm corresponding to the intrinsic emission peaks of cadmium sulfide and deep level defect,respectively.The intensity ratio of the two peaks can be adjusted by S ion implantation with different fluences.The electronic transport properties of the CdS nanobelts were characterized using a nanobelt field effect transistor(FET)device structure.The resulting threshold voltage,field-effect mobility and on/off ratio of the CdS FET were changed after S ion implantation owing to the defects caused by S ion implantation.(3)In situ investigation on the photoluminescence of 3D hierarchical branch CdS nanostructures coupling with Au nanoparticles.Three dimensional(3D)hierarchical branch CdS nanostructures were synthesized on Si substrate utilizing facile chemical vapor deposition(CVD)method.Au nanoparticles(NPs)were deposited on the surface of 3D hierarchical branch CdS by thermal evaporation method.a simple method that combined with photolithography technology to in situ investigate the photoluminescence of Au NPs decorated 3D hierarchical branch CdS nanostructures.The photoluminescence(PL)emission of Au nanoparticle decorated 3D hierarchical branch CdS nanostructures can be enhanced or quenched comparing to that of pure 3D hierarchical branch CdS nanostructures.The enhancement of the band gap emission is ascribed to the localized surface plasmons response(LSPR)of Au NPs and the local field enhancement induced the hot electrons on Au NPs transfer to the conduction band of the CdS,while the quenching is due to the light scattering of Au NPs and the electron transfer from the CdS to Au NPs.The results can be used to in situ investigate the performance of material,which is very important for the nano devices based on a single nanowire.And the results can also clarify the ambiguity in controlling the light emission enhancement and quenching of a semiconductor coupled with the LSPR of metal NPs,which is very useful for the design and applications of semiconductor and metal coupling for the creation of highly efficient solid-state emitters.