Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 153-159). Also available via the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 162-169).

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 1978 / Vita. / Includes bibliographical references. / Sc. D. / Sc. D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn whiskers can be found in flooring of data centers which can get inside electronic systems during equipment reorganization and movement and can also cause systems failure.Even though the topic of metal whiskers as reliability failure has been around for several decades to date, there is no successful method that can eliminate their growth. This thesis will give further insights towards the nature and behavior of Sn and Zn whiskers growth, and recommend a novel manufacturing technique that has potential to mitigate metal whiskers growth and extend life of many electronic devices.

No description available.

The continued miniaturization of interconnects results in performance and reliability issues for integrated circuit (IC) chips. As the critical dimension of Cu interconnects approaches dimensions near the mean free path of the metal (39.9 nm at room temperature), a rise in resistivity is observed. This phenomenon, termed resistivity size effect, is the result of electron scattering at grain boundaries and surfaces. Cobalt (Co) and ruthenium (Ru) are considered promising candidates to replace Cu as an interconnect metal because these metals exhibit a lower product of mean free path times bulk resistivity when compared with Cu. Additionally, given that electron scattering from grain boundaries is a major contributor to the resistivity-size effect in nanoscale interconnects, we investigate the electrodeposition of epitaxial Co, Ru, and Cu and demonstrate the capability of electrodeposition to fabricate epitaxial, single crystal metal films. Co, Ru, and Cu have a misfit strain that is tensile, zero, and compressive with the epitaxial Ru(0001) seed layer, respectively. This allowed for the study of every kind of misfit relationship that is possible in epitaxial film growth. Ultimately, the successful electrodeposition of Co and Cu epitaxial to a single crystal, conductive seed layer suggests the plausibility of electrodeposited, single crystal interconnects in future IC chips. Co electrodeposited as an epitaxial, single crystal film onto the Ru(0001) seed layers to finite thicknesses relevant for interconnect fabrication. Electrodeposition onto polycrystalline Ru seed layers, however, resulted in the growth of a rough, polycrystalline Co film with faceted growth. Despite a large misfit strain of 7.9%, the epitaxial electrodeposition of planar Co was achieved up to a thickness 75x beyond the calculated critical thickness for defect formation before a transition to island growth was observed. Thus, the importance of a conductive, single crystal seed layer, preferably with a minimal misfit strain with the depositing layer, is demonstrated. Metallic Ru was found to electrodeposit onto Ru(0001) as a porous layer comprised of (0001) oriented Ru crystallites. The presence of a porous Ru deposit was found to be independent of the seed layer, Ru metal ion source, and deposition mode used. An optimization of the deposition electrolyte to improve Ru atomic mobility is necessary to achieve the epitaxial electrodeposition of single crystal Ru. Finally, Cu demonstrated epitaxial growth on the Ru(0001) seed layer, with an out-of-plane epitaxial orientation relationship of Cu(111) | Ru(0001). The hexagonal close packed Ru(0001) seed layer allows Cu to deposit with two equivalent in-plane orientations; thus, the electrodeposited Cu film was determined to be a bicrystal, not a single crystal. While epitaxial deposition of Cu was achieved, a seed layer that permits only one orientation of Cu is required for a significant reduction in electron grain boundary scattering, hence, resistivity.

No description available.

Metal Organic Framework (MOF) materials, consisting of metal ions with organic linkers, have a functional cavity structure which can be utilized in applications such as catalyst, micro sensing, and gas absorption. Due to MOF materials' selective gas adsorption property, interest in MOF materials has intensified in the last few years, particularly for CO, CO₂, N₂, CH₄, and H₂. MOF materials are typically synthesized by reaction under hydrothermal conditions which yields a highly crystalline product. However, reaction under solvothermal condition typically requires long reaction times - from 8 hours up to several days depending upon the particular MOF material and the reaction conditions, such as solvent, temperature, and concentration. Other synthesis methods that have been developed to address these issues include microwave synthesis, sonochemical synthesis, and mechanochemical synthesis. Reaction time can be reduced to minutes under the high energy conditions of a microwave synthesis method. A solvent free synthesis can be achieved using the mechanochemical synthesis. The sonochemical synthesis method provides an environmentally friendly process. However, all of these synthesis methods above are batch processes and meet several difficulties in scalability and controllability. Herein, we introduce a new synthesis method for MOF materials which utilizes a continuous flow reactor process. To reduce the reaction time and solvent usage, and to maintain a high degree of the crystallinity are the goals of this study. Cu-BTC (BTC = Benzene, -1,3,5-Tricarboxylate ) or HKUST-1 Metal Organic Framework material was chosen to demonstrate the continuous flow reactor process since it has a simple MOF structure, consisting of Cu⁺² ions and BTC linkers, and has been widely studied for catalyst applications. The continuous flow synthesis method shows successful results of reduced residence time as low as 5 minutes, high crystal quality obtained, size control, and high yield with recycle solvent cooperation. The particle size control of MOF material has been shown crucial contributions in absorption application and is accomplished by adjusting the system temperature, flow rate, and solvent composition ratio. A water/ethanol mixture as the solvent in Cu-BTC synthesis reaction is environmentally friendly and easy to separate from the MOF product. In addition, the composition of water in solvent is the most influential factor to the crystal growth rate specifically in crystallization rate and nucleation rate. BTC is used in excess to achieve a production yield of about 97% based on Cu ion consumption. Since the Cu-BTC particles have a low solubility in the ethanol/water solution, they can be obtained easily using a dispersion/sonication method. The BTC rich supernatant can be recycled for use in the feed stream to maintain a high production rate, which can be beneficial for quick economic production in laboratory, as well as, commercial scale applications. / Graduation date: 2012