Fabrication and Analysis of Multilayer Structures for Coherent Thermal Emission

This dissertation describes a theoretical and experimental study on coherent thermal emission from thin-film multilayer structures. A novel multilayer structure consisting of a one-dimensional photonic crystal and a polar material (or a metal) is proposed as a coherent thermal-emission source. Surface electromagnetic waves can be excited at the edge of photonic crystal, enabling coherent emission characteristics (i.e., spectral- and directional-selectivity in the emissivity). A near-infrared coherent emission source is designed and fabricated using vacuum deposition and chemical vapor deposition techniques. Measurements were performed using a Fourier-transform infrared spectrometer and a laser scatterometer. The agreement between the resonance conditions obtained from experiments and the calculated dispersion relation confirms that surface waves at the photonic crystal-metal interface can be utilized to build coherent thermal-emission sources. The second part of this dissertation focuses on the energy propagation direction in near-field thermal radiation. The energy streamline method based on the Poynting vector is applied to near-field thermal radiation by incorporating the fluctuational electrodynamics, in which thermal emission is viewed as originated from random motion of electric dipoles at temperatures above absolute zero. It is shown that the Poynting vector is decoupled for each parallel wavevector component due to the randomness of thermal emission. The spectral radiative energy travels in infinite directions along curved lines; this is a fundamental characteristic of near-field thermal radiation. The findings in this dissertation are important for the design of near-field optical sensors and energy conversion devices.Ph.D.Committee Chair: Zhang, Zhuomin; Committee Member: Citrin, David; Committee Member: Graham, Samuel; Committee Member: Hesketh, Peter; Committee Member: Tsai, Benjami

Plasmon thermal conductivity of thin Au and Ag films

We investigated the thermal conductivity of surface plasmon polaritons (SPPs) propagating along thin Au and Ag films on a SiO$_2$ substrate with a Ti adhesive layer. To determine the propagation length and skin depth of SPPs along Au and Ag thin films, we numerically solved the dispersion relation while considering the size effect of the permittivity of metal. Additionally, we derived the spatial distribution of SPPs along the film thickness to analyze the effect of the Ti adhesive layer on the plasmon thermal conductivity of Au and Ag thin films. Our theoretical predictions revealed a decrease of approximately 30\% in plasmon thermal conductivity when considering the size effect of the permittivity of thin metal films. Furthermore, this causes the film thickness at which maximum thermal conductivity occurs to increase by about 30\%. Taking these factors into account, we calculated the optimal thickness of Au and Ag films, along with Ti adhesive layers, on SiO$_2$ substrates to be approximately 20 nm. By fabricating a sample with the optimal thickness of Au and Ag films, we experimentally demonstrated that the plasmon thermal conductivity of Au and Ag films can be as high as about 20\% of their electron contribution. This research will broaden the thermal design applications of ballistic thermal transport by SPPs propagating along thin metal coatings in microelectronics.Comment: 5 figure

Understanding The Impact Of IT Service Innovation On Firm Performance: The Case Of Cloud Computing

Recently we have witnessed a new kind of IT advancement. It is a phenomenon where various types of IT capabilities are centralized into data centers to ensure that such resources are available wherever and whenever they are needed. Cloud computing is the latest version of IT service practice reflecting such new IT trends. Although cloud computing is considered a paradigm shift of IT service design and delivery in IS communities and intrigues large amounts of interest from business entities, few studies have examined this new IT and business phenomenon. To better understand the organizational application of cloud computing, the current study aims to investigate economic payoff from cloud computing investment. Employing the event study methodology, we analyze 183 firm-level announcements regarding cloud computing adoption. The results indicate that cloud computing adoption announcements are associated with positive increases in the market value of the firm. In addition, we identified differences in the effect of cloud computing adoption on market returns according to strategic adoption intention, firm size, and industry sector. These results can be used as useful references for the firm’s decision-making about whether, when, and how to adopt cloud computing to maximize its business value