Optoelectronic Properties and Electronic Structures of One-dimensional Semiconducting/Piezoelectric Nanostructures with Sizes beyond the Quantum Confinement Regime
Date Issued
2012
Date
2012
Author(s)
Chen, Cheng-Ying
Abstract
In this thesis, we studied optoelectronic properties and electronic structures of one-dimensional (1-D) semiconducting/piezoelectric nanostructures with sizes beyond the quantum confinement regime and discussed their superior optoelectronic/photonic features as compared to their thin film of bulk counterpart.
First of all, since 1-D nanostructures have subwavelength diameters and large aspect ratios, which combined with the high permittivity of semiconductors lead to a strong optical anisotropy, we report a novel optically anisotropic metamaterial based on single crystalline ZnO nanowire arrays (NWAs) with highly oblique angles (75o–85o), exhibiting giant in-plane birefringence and optical polarization degree in photoluminescence emission. The in-plane birefringence ( 0.11) of oblique-aligned ZnO NWAs is almost one order of magnitude higher than that of ZnO bulk. The oblique-aligned NWAs not only allow important technological applications in passive photonic components but also benefit the development of the optoelectronic devices in polarized light sensing and emission.
Second, in 1-D nanostructures, with large surface-to-volume ratios and Debye lengths comparable to their diameters, their electronic and optoelectronic properties are strongly affected by the electronic structures at their surfaces. Here we systematically and in-depth investigated the correlation between electronic structures (especially at the surface) of 1-D (Er-doped) ZnO nanostrucrures and their optoelectronic properties through the following four subjects: (1) in situ probing the surface band bending (SBB) of the ZnO NWs using photoelectron spectroscopy in conjunction with the field-effect transistor measurements; (2) correlation between electronic structures of Er-Doped ZnO nanorod arrays and efficiency of 1.54 μm emission by studied by X-ray absorption spectroscopy; (3) enhanced near-band-edge emission of ZnO nanorods via the surface passivation; (4) correlation between photoresponse of ZnO nanobelts and the surface/interface effects. These studies are greatly beneficial for the 1-D nanostructure based device design of sensor and optoelectronic applications.
Finally, since ZnO is the wurtzite polar semiconductor and has the electromechanical coupling effect, piezoelectric characteristics of well-aligned ZnO NWAs were investigated for energy-harvesting nanodevices via its piezoelectricity. Besides, lead zirconate titanate [PbZr1−xTixO3 (PZT)] is a typical piezoelectric material, so the PbZr02Ti0.8O3 NWAs were also studied. This study is useful for optimizing the performance for nanogenerator applications.
Subjects
ZnO
PZT
nanowire
photodetector
optoelectric properties
nanogenerator
surface effects
Type
thesis
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