WWW.DISSERTATION.XLIBX.INFO
FREE ELECTRONIC LIBRARY - Dissertations, online materials
 
<< HOME
CONTACTS



Pages:   || 2 | 3 | 4 | 5 |   ...   | 21 |

«A Dissertation Presented to The Academic Faculty by Jesse I. Watjen In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in ...»

-- [ Page 1 ] --

STUDY OF RADIATIVE PROPERTIES OF THIN FILMS AND

NEAR-FIELD RADIATION FOR THERMOPHOTOVOLTAIC

APPLICATIONS

A Dissertation

Presented to

The Academic Faculty

by

Jesse I. Watjen

In Partial Fulfillment

of the Requirements for the Degree

Doctor of Philosophy in the

George W. Woodruff School of Mechanical Engineering

Georgia Institute of Technology

May 2016 Copyright © Jesse I Watjen 2016

STUDY OF RADIATIVE PROPERTIES OF THIN FILMS AND

NEAR-FIELD RADIATION FOR THERMOPHOTOVOLTAIC

APPLICATIONS

Approved by:

Dr. Zhuomin Zhang, Advisor Dr. Todd Sulchek George W. Woodruff School of George W. Woodruff School of Mechanical Engineering Mechanical Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Yogendra Joshi Dr. Martin Maldovan George W. Woodruff School of School of Physics Mechanical Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Shannon Yee George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Date Approved: March 8, 2016

ACKNOWLEDGEMENTS

I would like to express my gratitude to Dr. Zhuomin Zhang for his guidance over the past six years of my Ph.D. study, without whom this work would have never been possible. I would like to especially thank him for the enlightening conversations, and the valuable insights he has given me relating to my academic, professional, and personal endeavors. I would also like to thank my Committee members: Dr. Yogendra Joshi, Dr.

Shannon Yee, Dr. Todd Sulchek, and Dr. Martin Maldovan for their valuable feedback on my thesis work.

I would like to thank Dr. Christopher Muratore of the University of Dayton and Dr. Andrey Voevodin of the Air Force Research Laboratory, for their valuable input on crystallography, for the fabrication of the thin film tungsten samples. I would also like to thank Sampath Kommandur, Prabhakar Gulgunje, and Dr. Kan Wang of the Georgia Institute of Technology for their help with thermal property measurements of calibration materials. I would also like to thank the staff at the Georgia Tech Institute for Electronics and Nanotechnology for the advice and assistance with sample fabrication.

In addition, I would like to show my deepest appreciation to the current and former members of the Nanoscale Radiation Heat Transfer Group for their help and encouragement. In particular, I would like to thank Xianglei Liu for his help with the scattering theory coding for near-field grating simulations, and Dr. Trevor Bright for his help on the optical constant extraction and material characterization. I am also indebted to Bo Zhao whose tireless assistance with the near-field experimental work was invaluable, and the completion of this project would never have been possible without his help. I would like to thank all the other past and present group members for your friendship and support over these past few years.

Most importantly I would like to thank my wife Kaitlyn Watjen for her support throughout the years. Her bravery and strength have always been a source of inspiration

–  –  –

finish this work. Also, I would like to thank my parents, family, and friends for their understanding and encouragement throughout my graduate career.

Finally, I would like to thank the Department of Energy for partially supporting the work in this dissertation.

–  –  –

Table 3.1 Uncertainties of all major equipment used in the heat flux meter calibration.

Given is the instrument name used in the text as well as the manufacturer's make and model and the associated uncertainty.

Uncertainties shown should be interpreted as combined uncertainties.....57 Table 3.2 Results from the uncertainty analysis of the heat flux meter sensitivity.

Shown are all of the values where uncertainty was considered along with the change in the sensitivity and the contribution to the overall uncertainty.

The sensitivity found earlier is 6.87 V-cm2/mW, and the uncertainty found is 0.30 V-cm2/mW.

Table 4.1 A sample of high-performing grating geometries from the parametric sweep with the power output and efficiency at a gap spacing d = 20 nm.

The performance of a planar tungsten emitter is also shown

Table 5.1 List of samples used with the different pre- and post-deposition treatments indicated.

Annealing was performed at 800°C for 1h in vacuum. The native oxide on the Si substrate was removed by ion-cleaning.................84 Table 5.2 Thickness and the Drude-Lorentz model parameters of each sample obtained from fitting. The different pre- and post-deposition treatments are also indicated. Annealing was performed at 800°C for 1h in vacuum. The native oxide on the Si substrate was removed by ion-cleaning.................97

–  –  –

Figure 2.1 Illustration of reflection and transmission through a thin coherent film with multiple reflections shown.





Figure 2.2 Schematic showing the reflectivities and transmissivities for a thin film on thick substrate model.

Figure 2.3 Schematic showing near-field radiation between a hot and cold body.

.....19 Figure 2.4 Illustration showing the conventions for near-field radiation between semiinfinite and a nanoscale vacuum gap.

Figure 2.5 Desired geometry to simulate.

Figure 3.1 Reflection spectra for vacuum gaps sandwiched between undoped silicon.

The interference patterns caused by the gap spacing are clearly seen.......28 Figure 3.2 Picture of the reflectance accessory with the added components: a) Pike 10-spec, b) mounting bracket, c) 3 mm aperture sample holder, d) support bar. The sample and springs can also be seen.

Figure 3.3 a) Schematic of heat transfer system with important components labeled.

The sample is shown in blue. b) Picture of the system with a calibration sample in place.

Figure 3.4 Schematic of the important heat transfer measurement components with an illustration of the sample geometry.

Shown are the resistance heater, top and bottom thermocouples, heat flux meter, and silicon diode thermistor.38 Figure 3.5 Thermocouple configurations where the relevant measured temperature drop is shown. a) single thermocouple, b) duplexed thermocouple..........42 Figure 3.6 Heat flux meter used in this work.

Figure 3.7 Measured specific heats for the thin and thick PTFE samples.

Note the bump near 30°C corresponding to a change in the crystal phase..............48 Figure 3.8 Thermal conductivities for both PTFE sizes

Figure 3.9 Heat rates and temperatures for three calibration measurements.

.............53 Figure 3.10 Heat rates and temperatures for three calibration measurements..............54 Figure 3.11 Results of thermocouple calibration experiment. The markers are experimental data, while the ideal response is shown in black..................59

–  –  –

Figure 4.2 a) Electrical power output in log scale versus period and grating height.

Values shown only at the filling fraction with the highest power. b) Conversion efficiency versus period and grating height. Values shown only at the filling fraction with the highest efficiency. Note that all calculations are at a gap spacing of 20 nm.

Figure 4.3 Electrical power output and conversion efficiency versus grating period.

The gray section highlighted represents the performance versus a flat tungsten emitter.

Figure 4.4 Electrical power output and conversion efficiency versus grating period only for geometries with a minimum feature size greater than 10 nm and an aspect ratio less than 35.

The gray section highlighted represents the performance versus a flat tungsten emitter.

Figure 4.5 Power output (solid lines) and conversion efficiency (dashed lines) for the selected grating (shown with markers) and for a planar tungsten slab (no markers).

Performance comparison for a grating with H  500 nm, P  50 nm, f  0.8 Figure 4.6 by varying a single geometric parameter: a) filling fraction, b) period, c) grating height.

–  –  –

Figure 4.8 Spectral energy transmission coefficient for grating and planar geometries.

The bandgap of 8.4  1014 rad/s is shown with a dotted line.

–  –  –

Transmission coefficient  y (, k y ) versus angular frequency and reduced Figure 4.10 y-dimension wavevector for the planar tungsten emitter.

Figure 5.1 GIXRD profiles for all four samples with the phase and crystal orientation denoted.

Note that samples W01 and W02 were both annealed and present the same crystal phase.

–  –  –

Figure 5.3 Results of the extracted refractive index for sample W04: a) real part of refractive index, b) imaginary part.

Multiple local solutions are shown, and points with a higher color saturation have less RMS error.................90 Figure 5.4 Measured and fitted spectral radiative properties for the two annealed samples: (a) W01 and (b) W02.

Figure 5.5 Dielectric function obtained for the two annealed samples: (a) Real part;

(b) Imaginary part. The data from Palik [37] are shown for comparison.

Note that 1 is negative in the spectral region of interest.

Figure 5.6 Measured and fitted spectral radiative properties for the two unannealed samples: (a) W03 (ion-cleaned) and (b) W04.

Figure 5.7 Real and imaginary parts of the dielectric function of the two unannealed samples.

Figure 5.8 The penetration depths of all four samples calculated from the dielectric function models.

Figure 5.9 Spectral normal emissivity of all studied films and the literature value from Palik [37].

Figure 6.1 Heat transfer coefficient for gaseous conduction for different gap spacings at various vacuum pressures.

The minimum radiation heat transfer coefficient is shown for comparison.

Figure 6.2 Layout of the sample pattern with SiO2 posts shown in blue on a silicon substrate.

The spacing S is demonstrated.

Figure 6.3 Percentage of radiation to total heat transfer in samples versus gap spacing.

Results are shown for all four pattern spacings. The temperature drop used is 20K.

Figure 6.4 Finite element simulation of one unit cell of the silicon samples with 100 grams of load; a) deflection in the post, b) deflection in the silicon.

The deflection is shown in nm. The sample geometry shown is a 500 m spacing with 400 nm post height.

Figure 6.5 Performance of silicon as a sample material.

a) FTIR simulations at various gap spacings, b) radiative heat flux into the low-temperature Si plate.

x Figure 6.6 Performance of silicon dioxide as a sample material.

a) FTIR simulations at various gap spacings, b) radiative heat flux into the low-temperature SiO2 plate.

Performance of doped silicon at a doping concentration of 1017 cm-3 as a Figure 6.7 sample material. a) FTIR simulations at various gap spacings, b) radiative heat flux into the low-temperature d-Si plate compared with a semiinfinite thickness.

Performance of doped silicon at a doping concentration of 1018 cm-3 as a Figure 6.8 sample material. a) FTIR simulations at various gap spacings, b) radiative heat flux into the low-temperature d-Si plate compared with a semiinfinite thickness.

Performance of doped silicon at a doping concentration of 5×1018 cm-3 as Figure 6.9 a sample material. a) FTIR simulations at various gap spacings, b) radiative heat flux into the low-temperature d-Si plate compared with a semi-infinite thickness.

Figure 6.10 Measurement and prediction for the reflectance and transmittance for doped silicon wafers.

Transmittance is shown in blue while reflectance is shown in black, and the measurements are shown using dashed lines....131 Figure 6.11 a) refractive index and b) extinction coefficient extracted for the doped silicon wafers. Shown are the values extracted using a point-by-point algorithm, as well as the predicted optical constants from Palik with an added Drude model, and from Basu at a doping level of 2×1018 cm-3.....133 Refractive index and extinction coefficient shown between 100 cm-1 and Figure 6.12 10000 cm-1 (1-100 m)

Figure 6.13 Radiative heat flux using doped silicon as a function of gap spacing.

Calculations are done at a temperature difference of 20°C. The heat flux for blackbody radiation is also shown.

Figure 6.14 Calculation of the infrared reflectance of samples with different gap spacings shown in the range of FTIR measurements

Figure 6.15 Bowing from a typical silicon wafer.

a) measurement of the surface deflection of a 100 mm wafer. The bottom measurement is inverted for comparison. Boxed region is shown in b) where two 1 cm pieces detached and recentered to show individual bowing.

Figure 6.16 Deflection over a 100 mm wafer.

Top and bottom surface profiles are shown at three angles each.

–  –  –

Figure 6.18 Process flow for creating samples.

a) wafer cleaning, b) oxide deposition, c-g) pattern transfer through photolithography, h) dicing to 1 cm pieces, i) mating a patterned and cleaned piece.

Confocal microscope image of a 200 m pattern.

Figure 6.19 Confocal microscope image of a 10 m pattern.



Pages:   || 2 | 3 | 4 | 5 |   ...   | 21 |


Similar works:

«Erkenn DOI 10.1007/s10670-008-9149-3 ORIGINAL ARTICLE Dear Haecceitism Delia Graff Fara Received: 27 July 2007 / Accepted: 1 December 2008 Ó Springer Science+Business Media B.V. 2009 Abstract If a counterpart theorist’s understanding of the counterpart relation precludes haecceitist differences between possible worlds, as David Lewis’s does, how can he admit haecceitist possibilities, as Lewis wants to? Lewis (Philosophical Review 3–32, 1983; On the Plurality of Worlds, 1986) devised...»

«Ideas and considerations for detailed design and naming for Ōtautahi North Western Cluster of Schools A Ngāi Tūāhuriri Perspective An Example of Modern Māori Learning Environments and associated Cultural Identifiers Te Whare Maahunui Tuahiwi Marae Home of Ngāi Tūāhuriri Mana Whenua 1 Wednesday, 14 October 2015 Table of Contents Whāinga / Aim Kaupapa rapunga whakaaro / Philosophy Mana Whenua / Te Ngāi Tūāhuriri Te Ngāi Tūāhuriri/ Mana Whenua Ngāi Tahu Whānui and Te Rūnanga o...»

«Humanity at the Turning Point: Rethinking Nature, Culture and Freedom (Sonja Servomaa, editor). Helsinki, Finland: Renvall Institute for Area and Cultural Studies, 2006.Beyond Tolerance: Globalization, Freedom, and Religious Pluralism Douglas W. Shrader1 Distinguished Teaching Professor & Chair of Philosophy SUNY Oneonta Oneonta, NY Abstract: If “Globalization” is to mean something other than imposing a single set of uniform, unexamined, and unchallengeable ideas on the entire human race,...»

«MODELING, DESIGN AND ENERGY MANAGEMENT OF FUEL CELL SYSTEMS FOR AIRCRAFT A Dissertation Presented to The Academic Faculty by Thomas Heenan Bradley In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Mechanical Engineering Georgia Institute of Technology December, 2008 Copyright © Thomas Heenan Bradley 2008 MODELING, DESIGN AND ENERGY MANAGEMENT OF FUEL CELL SYSTEMS FOR AIRCRAFT Approved by: Dr. David E. Parekh, Advisor Dr. William J. Wepfer School of...»

«ABSTRACT Title of document: DENOVO SYNTHESIZED FATTY ACIDS AS REGULATORS OF MILK FAT SYNTHESIS Diwakar Vyas, Doctor of Philosophy, 2011 Directed By: Professor Richard A. Erdman Department of Animal and Avian Sciences The objectives of the dissertation research were to determine the role of denovo synthesized fatty acids (DNFA) in the regulation of milk fat synthesis. Milk fat responses to increasing amounts of shortand medium-chain fatty acids (SMCFA), added in the proportion as synthesized...»

«Cosmo Girls, Cheetah Boys and Creatures Unlike Any Other: Relationship Advice and Social Change in North America by Sarah Kathryn Knudson A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Sociology University of Toronto © Copyright by Sarah Knudson 2012 Cosmo Girls, Cheetah Boys and Creatures Unlike Any Other: Relationship Advice and Social Change in North America Sarah Kathryn Knudson Doctor of Philosophy Department of Sociology...»

«POOL AND FLOW BOILING OF NOVEL HEAT TRANSFER FLUIDS FROM NANOSTRUCTURED SURFACES A Dissertation Presented to The Academic Faculty by Aravind Sathyanarayana In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology December 2013 Copyright © 2013 by Aravind Sathyanarayana POOL AND FLOW BOILING OF NOVEL HEAT TRANSFER FLUIDS FROM NANOSTRUCTURED SURFACES Approved by: Dr. Yogendra Joshi,...»

«Stony Brook University The official electronic file of this thesis or dissertation is maintained by the University Libraries on behalf of The Graduate School at Stony Brook University. © Allll Riightts Reserved by Autthor. © A R gh s Reserved by Au hor Ecogeographic Variation in Neandertal Dietary Habits: Evidence from Microwear Texture Analysis A Dissertation Presented by Sireen El Zaatari to The Graduate School in Patrial fulfillment of the Requirements for the Degree of Doctor of...»

«DESIGN OF FAULT TOLERANT CONTROL SYSTEMS by Benjamin Erik Walker A dissertation submitted to the faculty of The University of North Carolina at Charlotte in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering Charlotte 2012 Approved by: Dr. Bharat Joshi Dr. Yogendra Kakad Dr. James Conrad Dr. Mehdi Miri Dr. Edgar Munday ii ©2012 Benjamin Erik Walker ALL RIGHTS RESERVED iii ABSTRACT BENJAMIN ERIK WALKER. Design of fault tolerant control...»

«Visualizing Users, User Communities, and Usage Trends in Complex Information Systems Using Implicit Rating Data Seonho Kim Dissertation submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science and Applications Advisory Committee: Edward A. Fox, Chair Weiguo Fan Christopher North Deborah Tatar Ricardo da Silva Torres April 14, 2008 Blacksburg, Virginia Keywords:...»

«OREGON STATE UN VERS TY LIBRARIES 1111 1111 11 11111 1111 12 0003896558 Tillamook Prehistory and Its Relation to the Northwest Coast Culture Area by Thomas M. Newman /-iPARTMENT OF ANTHROPfottLIBRARY, TILLAMOOK PREHISTORY AND ITS RELATION TO THE NORTHWEST COAST CULTURE AREA by THOMAS M. NEWMAN A THESIS Presented to the Department of Anthropology and the Graduate School of the University of Oregon in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 1959...»

«kwb.45-variantology_inhalt_neu:kwb.31-variantology_end_5.0 19.02.10 14:12 Seite 215 david link Scrambling T-R-U-T-H Rotating Letters as a Material Form of Thought “Know that the secrets of God and the objects of His science, the subtle realities and the dense realities, the things of above and the things from below, belong to two categories: there are numbers and there are letters. The secrets of the letters are in the numbers, and the epiphanies of the numbers are in the letters. The numbers...»





 
<<  HOME   |    CONTACTS
2016 www.dissertation.xlibx.info - Dissertations, online materials

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.