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You searched for +publisher:"Georgia Tech" +contributor:("Dr. Zhuomin Zhang"). Showing records 1 – 3 of 3 total matches.

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1. Wang, Xiaojia. Study of the radiative properties of aligned carbon nanotubes and silver nanorods.

Degree: PhD, Mechanical Engineering, 2011, Georgia Tech

Arrays of nanotubes/rods made of appropriate materials can yield unique radiative properties, such as large absorption and optical anisotropy, with broad applications from high-efficiency emitters and absorbers for energy conversion to the polarization conversion via anisotropic responses. The objective of this dissertation is to investigate the radiative properties of arrays formed by aligned carbon nanotubes (CNTs) and silver nanorods (AgNRs). The CNT arrays used in the present study consist of multi-walled CNTs synthesized vertically on silicon substrates using thermal chemical vapor deposition. Their close-to-unity absorptance is demonstrated by measuring the directional-hemispherical reflectance in the visible and near-infrared spectral ranges using an integrating sphere. The bidirectional reflectance distribution function and angle-resolved reflectance were measured at the 635-nm wavelength. The results demonstrate that high-absorptance CNT arrays may be diffusely or specularly reflecting and have important applications in radiometry. Theoretical modeling based on the effective medium theory (EMT) and reflectivity of an anisotropic medium are developed to explain the high absorption and polarization dependence. The effective optical constants of the CNT array for both ordinary and extraordinary polarizations are quantitatively determined by fitting the angle-resolved reflectance. The AgNR arrays used in the present study were fabricated using oblique angle deposition, which results in inclined Ag nanorods that can be modeled as an effective homogenous and optically anisotropic thin film. The spectral and directional radiative properties of AgNRs grown on different substrates, including a glass slab with a silver film, and compact disc gratings, were characterized at the 635-nm and 977-nm wavelengths for different polarizations. The results are analyzed based on the EMT, rigorous coupled-wave analysis, and anisotropic thin-film optics. The results of this dissertation help gain a better understanding of radiative properties of anisotropic nanostructures for potential applications in high-efficiency energy conversion, radiometric devices, and optical systems. Advisors/Committee Members: Dr. Zhuomin Zhang (Committee Chair), Dr. Baratunde A. Cola (Committee Member), Dr. Peter J. Hesketh (Committee Member), Dr. Thomas K. Gaylord (Committee Member), Dr. Yiping Zhao (Committee Member).

Subjects/Keywords: Thermal radiation; Nanoarray; Effective medium; Anisotropic wave propagation; BRDF; Scattering; Nanotubes; Nanostructured materials; Carbon; Radiative transfer; Silver

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APA (6th Edition):

Wang, X. (2011). Study of the radiative properties of aligned carbon nanotubes and silver nanorods. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42871

Chicago Manual of Style (16th Edition):

Wang, Xiaojia. “Study of the radiative properties of aligned carbon nanotubes and silver nanorods.” 2011. Doctoral Dissertation, Georgia Tech. Accessed May 09, 2021. http://hdl.handle.net/1853/42871.

MLA Handbook (7th Edition):

Wang, Xiaojia. “Study of the radiative properties of aligned carbon nanotubes and silver nanorods.” 2011. Web. 09 May 2021.

Vancouver:

Wang X. Study of the radiative properties of aligned carbon nanotubes and silver nanorods. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 May 09]. Available from: http://hdl.handle.net/1853/42871.

Council of Science Editors:

Wang X. Study of the radiative properties of aligned carbon nanotubes and silver nanorods. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42871


Georgia Tech

2. Zhu, Qunzhi. Modeling and Measurements of the Bidirectional Reflectance of Microrough Silicon Surfaces.

Degree: PhD, Mechanical Engineering, 2004, Georgia Tech

Bidirectional reflectance is a fundamental radiative property of rough surfaces. Knowledge of the bidirectional reflectance is crucial to the emissivity modeling and heat transfer analysis. This thesis concentrates on the modeling and measurements of the bidirectional reflectance for microrough silicon surfaces and on the validity of a hybrid method in the modeling of the bidirectional reflectance for thin-film coated rough surfaces. The surface topography and the bidirectional reflectance distribution function (BRDF) of the rough side of several silicon wafers have been extensively characterized using an atomic force microscope and a laser scatterometer, respectively. The slope distribution calculated from the surface topographic data deviates from the Gaussian distribution. Both nearly isotropic and strongly anisotropic features are observed in the two-dimensional (2-D) slope distributions and in the measured BRDF for more than one sample. The 2-D slope distribution is used in a geometric-optics based model to predict the BRDF, which agrees reasonably well with the measured values. The side peaks in the slope distribution and the subsidiary peaks in the BRDF for two anisotropic samples are attributed to the formation of {311} planes during chemical etching. The correlation between the 2-D slope distribution and the BRDF has been developed. A boundary integral method is applied to simulate the bidirectional reflectance of thin-film coatings on rough substrates. The roughness of the substrate is one dimensional for simplification. The result is compared to that from a hybrid method which uses the geometric optics approximation to model the roughness effect and the thin-film optics to consider the interference due to the coating. The effects of the film thickness and the substrate roughness on the validity of the hybrid method have been investigated. The validity regime of the hybrid method is established for silicon dioxide films on silicon substrates in the visible wavelength range. The proposed method to characterize the microfacet orientation and to predict the BRDF may be applied to other anisotropic or non-Gaussian rough surfaces. The measured BRDF may be used to model the apparent emissivity of silicon wafers to improve the temperature measurement accuracy in semiconductor manufacturing processes. The developed validity regime for the hybrid method can be beneficial to future research related to the modeling for thin-film coated rough surfaces. Advisors/Committee Members: Dr. Zhuomin Zhang (Committee Chair), Dr. Andrei G. Fedorov (Committee Member), Dr. Andrew F. Peterson (Committee Member), Dr. Dennis W. Hess (Committee Member), Dr. J. Robert Mahan (Committee Member).

Subjects/Keywords: Light Scattering; Slope distribution; Thin-film coating; Rough surface; AFM; BRDF; Thin films Testing; Silicon Testing; Reflectance; Light Scattering

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APA (6th Edition):

Zhu, Q. (2004). Modeling and Measurements of the Bidirectional Reflectance of Microrough Silicon Surfaces. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/5062

Chicago Manual of Style (16th Edition):

Zhu, Qunzhi. “Modeling and Measurements of the Bidirectional Reflectance of Microrough Silicon Surfaces.” 2004. Doctoral Dissertation, Georgia Tech. Accessed May 09, 2021. http://hdl.handle.net/1853/5062.

MLA Handbook (7th Edition):

Zhu, Qunzhi. “Modeling and Measurements of the Bidirectional Reflectance of Microrough Silicon Surfaces.” 2004. Web. 09 May 2021.

Vancouver:

Zhu Q. Modeling and Measurements of the Bidirectional Reflectance of Microrough Silicon Surfaces. [Internet] [Doctoral dissertation]. Georgia Tech; 2004. [cited 2021 May 09]. Available from: http://hdl.handle.net/1853/5062.

Council of Science Editors:

Zhu Q. Modeling and Measurements of the Bidirectional Reflectance of Microrough Silicon Surfaces. [Doctoral Dissertation]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/5062


Georgia Tech

3. Chen, Yu-Bin. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.

Degree: PhD, Mechanical Engineering, 2007, Georgia Tech

Radiative properties of a material is the core of thermal science and optics, which play critical roles in modern technologies, including microelectronics, energy conversion, and nanotechnology. The key to modify or enhance radiative properties is employing one-, two-, and three-dimensional (1, 2, and 3D) periodic micro/nanostructures. Since their applications are not fully uncovered and very few comprehensive studies are available, the objective of this dissertation is to explore applications of periodic micro/nanostructures with modified radiative properties in modern technologies through both numerically and experimentally investigations. Theses representative applications include the thermal control in rapid thermal processing, the design of a wavelength-selective radiator for thermophotovoltaic systems, and the nanothermal manufacturing. The theoretical foundation of the study is built on the rigorous coupled-wave analysis (RCWA) for numerical calculation of the far-field radiative properties and the electromagnetic field distribution in the near-field regime. Measurements of diffraction efficiencies are conducted on fabricated 1D and 2D periodic silicon microstructures with a laser scatterometer/diffractometer with high angular resolution. The diffraction efficiency can be employed for non-contact surface profile inspection tool because it strongly depends on structure patterns. For better temperature control during rapid thermal processing, the dissertation performs a parametric study on radiation absorption of a generic CMOS device together with its simplified nanoscale structures. The applicability of approximation models, which homogenize micro/nanostructures into a film, is also evaluated. Next, a new concept of complex gratings is proposed for actively tailoring the radiative properties and serving as a thermophotovoltaic (TPV) radiator. The radiator exhibits a wide-band and angle-independent high transverse magnetic wave emittance matching the bandgap of TPV cells so that the energy conversion efficiency can be improved. Furthermore, the nanoscale metallic slit arrays show polarization-dependant enhanced transmission and highly localized electromagnetic energy density, which hold promising potentials in nanothermal manufacturing. Three submicrometer metallic slit arrays are fabricated on top of a silicon substrate. Their spectral transmittance is measured with a Fourier-transform infrared spectrometer and largely agrees with RCWA modeling results. In short, the dissertation clearly demonstrates that precise control and tuning of radiative properties using micro/nanofabrication are not only feasible but also may have numerous technological impacts. Advisors/Committee Members: Dr. Zhuomin Zhang (Committee Chair), Dr. F. Levent Degertekin (Committee Member), Dr. Gee-Kung Chang (Committee Member), Dr. Pei-feng Hsu (Committee Member), Dr. Peter J. Hesketh (Committee Member).

Subjects/Keywords: Micro/Nanostructures; Gratings

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chen, Y. (2007). Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/14470

Chicago Manual of Style (16th Edition):

Chen, Yu-Bin. “Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.” 2007. Doctoral Dissertation, Georgia Tech. Accessed May 09, 2021. http://hdl.handle.net/1853/14470.

MLA Handbook (7th Edition):

Chen, Yu-Bin. “Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.” 2007. Web. 09 May 2021.

Vancouver:

Chen Y. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2021 May 09]. Available from: http://hdl.handle.net/1853/14470.

Council of Science Editors:

Chen Y. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/14470

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