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Routes to control the crystal structure, morphology and aligned growth of quasi-one-dimensional zinc-cadmium-selenium nanostructures by metalorganic chemical vapor deposition

Posted on:2008-12-07Degree:Ph.DType:Dissertation
University:The Chinese University of Hong Kong (Hong Kong)Candidate:Liu, ZhuangFull Text:PDF
GTID:1441390005458129Subject:Physics
Abstract/Summary:
Studying quasi-one-dimensional (1D) semiconductor nanostructures is an attractive and active research field in nanoscience and nanotechnology. Their controllable growth is the foundation for observing novel properties and fabricating useful nano-devices and is also a challenge.;We have studied the control of the structure, morphology and alignment of Zn-Cd-Se 1D nanostructures by fine tuning their growth conditions and judiciously choosing substrates in a metalorganic chemical vapor deposition (MOCVD) reactor. We found that the products are zincblende structured nanoneedles at relatively low temperatures and pressures, and wurtzite structured nanowires at high temperatures and pressures. We have fabricated aligned 1D nanostructures of different chemical compositions by exploiting the epitaxial relationship between the lattices of Zn-Cd-Se system and GaAs substrate. From the systematic studies of the orientations of the aligned samples, we demonstrated that they can be controlled by the crystallographic surface of the substrate. We also found that the orientation can be affected by the growth temperature. Three growth models are suggested to explain the aligned growth for zincblende and wurtzite 1D nanostructures and complex shaped three-bladed nanoswords. Observations and angular measurements of the orientations and growth directions by electron microscopy and analyses by pole stereographs offer supporting evidences for the models. Polarized photoluminescence studies of individual CdSe nanowires obtained under controlled growth have been achieved.;We believe that our work in perfecting the fabrication of aligned 1D semiconductor nanostructures and control of their morphology, crystal structure and orientation will shed more light on the understanding on 1D physics and advancement in nanotechnology.
Keywords/Search Tags:Growth, Nanostructures, Morphology, Aligned, Chemical
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