Surface and Interface Characterization of Thin Film Energy Devices

Download or read book Surface and Interface Characterization of Thin Film Energy Devices written by Wŏn-yong Yi and published by Stanford University. This book was released on 2010 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin film devices for energy conversion have become a vital area of research to achieve high performance with low cost. As the surface-to-volume ratio becomes significant, the fundamental physics of the surface and interface microstructures and the reaction mechanisms are important to developing such energy devices or processes. My Ph.D. research is thus focus on surface and interface characterization of energy materials for thin film devices with engineered components fabricated by novel technologies. The first part of this dissertation discusses how surface microstructures influence fuel cell performance. According to the high resolution characterization of surface grain boundaries in solid oxide ion conductors, oxygen vacancy segregation at grain boundaries was observed, indicating that the grain boundaries can be more active sites for oxygen incorporation into the electrolyte. This preferred surface reaction at grain boundaries was verified by AC impedance spectroscopy. In addition, using atomic force microscopy, the local rearrangement of charged species on the oxide surface was investigated as a function of time and temperature to quantitatively analyze the diffusivity of oxygen vacancies on the surface. The second part discusses investigation of quantum confined structures that was aimed at contributing to the development of new solar cell architectures. The electronic properties of quantum confined structures, fabricated by atomic layer deposition (ALD), were characterized by scanning tunneling microscopy. In particular, the band gap of lead sulfide quantum well was tuned as a function of well thickness and potential barrier height. In addition, various nano-patterning techniques were developed to fabricate higher-order quantum confined structures, including area-selective ALD.