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As device dimensions in integrated circuits scale down, there is an increasing need to deposit ultra-thin, smooth, continuous films for use in applications such as the liner in back end processing. The liner must have good adhesion to both Cu and the dielectric, act as a Cu diffusion barrier, and be conductive enough to allow the electroplating of Cu. Ruthenium (Ru) has been considered as a possible material to be implemented into the liner due to its low electrical resistivity, high thermal and chemical stability, and negligible solubility with copper. Chemical vapor deposition (CVD) is an attractive growth technique for Ru films because it allows conformal deposition in high-aspect ratio features. However, there are some limitations that must be overcome in the deposition of Ru films. CVD Ru films suffer from poor nucleation on oxide and nitride substrates. Poor nucleation leads to rough, large-grained polycrystalline columnar films, which may not coalesce into a continuous film until the thickness greatly exceeds the requirements for the liner. This dissertation presents surface chemistry and film growth studies involving Ru CVD and focuses on improving the nucleation and properties of Ru films. In situ surface analysis techniques including X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) were used to study the fundamental adsorption behavior of the Ru precursor, (2,4- dimethylpentadienyl)(ethylcyclopentadienyl)Ru or DER, on polycrystalline Ta, both with and without iodine adsorbed on the Ta. Based upon these results, CVD films were grown using DER/O₂, and it was shown that nucleation and film properties can be improved by the addition of methyl iodide. Ru films grown using DER/O₂ show sparse nucleation, which leads to very rough surface topography and large polycrystalline columnar grains. The addition of methyl iodide during growth significantly improves nucleation and results in smoother, smaller-grained films. Iodine adsorbs on the initially-formed Ru islands and continuously segregates through the film to the surface during the entire deposition. In addition, CVD films grown with Ru₃(CO)₁₂ were studied. Use of the Ru₃(CO)₁₂ precursor results in thin, ultra-smooth films that show little to no columnar grain structure. / text

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CIVINS / Carbon nanotubes (CNTs) exhibit exceptional electrical, thermal, and mechanical properties that could potentially transform such diverse fields as composites, electronics, cooling, energy storage, and biological sensing. For the United States Navy, composites potentially provide a significant decrease in lifetime maintenance costs of ships by eliminating hull corrosion. A stronger composite could also improve naval ship survivability or increase combat payloads by reducing the hull weight of ships and submarines. Further, cooling requirements of ship borne electronics have grown exponentially and represent a significant weight penalty for advanced ship designs. Any improvement in thermal transport could significantly improve future naval ship designs. In order to realize these benefits, methods must be discovered to fully characterize CNT growth mechanisms, consistently produce CUTs in manufacturable quantities, and to integrate CUTs into macroscale structures which reflect the properties of individual CUTs. While growth of CNTs in laboratory scale chemical vapor deposition (CVD) tube furnaces has shown great promise, existing low cost tube furnace designs limit the researcher's ability to fully separate critical reaction parameter such as temperature and flow profiles and limit the rate of temperature change during the growth process. Conventional tube furnace designs also provide limited mechanical access to the growth Site and prevent optical monitoring of the growth site, removing the ability to observe and interact in situ during growth. This thesis presents the SabreTube, a low-cost desktop cvD apparatus that decouples temperature and flow variables, provides mechanical and optical access to the reaction site during growth, and provides modular fixturing to enable versatile experimentation with and characterization of CUT growth mechanisms. This thesis also presents the Nanosled, a device designed to translate a substrate through a CVD furnace. / Contract number: N62271-97-G-0026. / CIVINS

Discover of new energy sources and solutions are one of the important global issues nowadays, which has a big impact on economy as well as environment. One of the methods to help to mitigate this issue is to recover wasted heat, which is produced in large quantities by the industry, through vehicle exhausts and in many other situations where we consume energy. One way to do this would be using thermoelectric (TE) materials, which enable direct interconversion between heat and electrical energy. This thesis investigates how the novel material combinations and nanotechnology could be used for fabricating more efficient TE materials and devices. The work presents synthesis, processing, and electrical characterization of group IV materials for TE applications. The starting point is epitaxial growth of alloys of group IV elements, silicon (Si), germanium (Ge) and tin (Sn), with a focus on SiGe and GeSn(Si) alloys. The material development is performed using chemical vapor deposition (CVD) technique. Strained and strain-relaxed Ge1-x Snx (0.01≤x≤0.15) has been successfully grown on Ge buffer and Si substrate, respectively. It is demonstrated that a precise control of temperature, growth rate, Sn flow and buffer layer quality is necessary to overcome Sn segregation and achieve a high quality GeSn layer. The incorporation of Si and n- and p-type dopant atoms is also investigated and it was found that the strain can be compensated in the presence of Si and dopant atoms.  Si1-xGexlayers are grown on Si-on-insulator wafers and condensed by oxidation at 1050 ᵒC to manufacture SiGe-on-insulator (SGOI) wafers. Nanowires (NWs) are processed, either by sidewall transfer lithography (STL), or by using conventional lithography, and subsequently manufactured into nanoscale dimensions by focused ion beam (FIB) technique. The NWs are formed in an array, where one side is heated by a resistive heater made of Ti/Pt. The power factor of NWs is measured and the results are compared for NWs manufactured by different methods. It is found that the electrical properties of NWs fabricated with FIB technique can be influenced due to Ga doping during ion milling. Finally, the carrier transport in SiGe NWs formed on SGOI samples is tailored by applying a back-gate voltage on the Si substrate. In this way, the power factor is improved by a factor of 4. This improvement is related to the presence of defects and/or small fluctuation of nanowire shape and Ge content along the NWs, generated during processing and condensation of SiGe layers. The SiGe results open a new window for operation of SiGe NWs-based TE devices in the new temperature range of 250 to 450 K. / <p>QC 20160907</p>

As part of the effort to increase the reliability of the MMT Observatory (MMTO) 6.5m Primary Mirror Coating System, the specified filament has changed from a configuration in which the aluminum charge is hand wound around a tungsten filament to a configuration in which the aluminum is integrally wound with the tungsten at the time of filament manufacture. In the MMTO configuration, this filament consists of the three strands of tungsten wire and one strand of aluminum wire. In preparation of a full system test utilizing two hundred filaments fired simultaneously, an extensive testing program was undertaken to characterize these filaments using a four filament configuration in the MMTO small coating chamber (0.5m) and then a forty filament configuration in the University of Arizona Steward Observatory coating chamber (2m). The testing using the smaller coating chambers has shown these filaments provide very predicable coatings from test to test, and with the proper heating profile, these filaments greatly reduce the likelihood of aluminum drips. The initial filament design was modified during the course of testing by shortening the unwound filament length to closer match the aluminum load required in the MMTO coating chamber. This change increased the aluminum deposition rates without increasing the power delivered of the filament power supplies (commercial welders). Filament power levels measured at the vacuum chamber feedthroughs, currents, and deposition rates from multiple coating tests, including a full system test, are presented.

In recent years, quasi-one-dimensional materials have attracted a lot of research attention due to their remarkable properties, and their potential as building blocks for nanoscale electronic and optoelectronic devices. A modified chemical vapor deposition (CVD) method has been used to synthesize ZnO nanowires. Electron microscopy and other characterization techniques show that nanowires having distinct morphologies when grown under different conditions. The effects of reaction parameters including reaction time, temperature, carrier gas flow rate, substrates and catalyst material upon the size, shape, and density of ZnO nanowire arrays have been investigated. Excitonic solar cells —including Gratzel-type cells, organic and hybrid organic/inorganic solar cells—are promising devices for inexpensive, large-scale solar energy conversion. Hybrid organic/inorganic solar cells are made from composites of conjugated polymers with nanostructure metal oxides, in which the polymer component serves the function of both light absorber and hole conductor, and the ZnO nanowire arrays act as the electron conductors. Organic solar cells have been fabricated from environmentally friendly water-soluble polymers and ZnO nanowire arrays.

Thesis advisor: Dunwei Wang / When their electrodes are made of nanomaterials or materials with nanoscale features, devices for energy conversion and energy storage often exhibit new and improved properties. One of the main challenges in material science, however, is to synthesize these nanomaterials with designed functionality in a predictable way. This thesis presents our successes in synthesizing TiSi₂ nanostructures with various complexities using a chemical vapor deposition (CVD) method. Attention has been given to understanding the chemistry guiding the growth. The governing factor was found to be the surface energy differences between various crystal planes of orthorhombic TiSi₂ (C54 and C49). This understanding has allowed us to control the growth morphologies and to obtain one-dimensional (1D) nanowires, two-dimensional (2D) nanonets and three-dimensional (3D) complexes with rational designs by tuning the chemical reactions between precursors. Among all these morphologies, the 2D nanonet, which is micrometers wide and long but only approximately 15 nm thick, has attracted great interest because it is connected by simple nanostructures with single-crystalline junctions. It offers better mechanical strength and superior charge transport while preserving unique properties associated with the small-dimension nanostructure, which opens up the opportunity to use it for various energy related applications. In this thesis we focus on its applications in lithium ion batteries. With a unique heteronanostructure consisting of 2D TiSi₂ nanonets and active material coating, we demonstrate the performances of both anode and cathode of lithium ion batteries can be highly improved. For anode, Si nanoparticles are deposited as the coating and at a charge/discharge rate of 8400 mA/g, we measure specific capacities >1000 mAh/g with only an average of 0.1% decay per cycle over 100 cycles. For cathode, V₂O₅ is employed as an example. The TiSi₂/V₂O₅ nanostructures exhibit a specific capacityof 350 mAh/g, a power rate up to 14.5 kW/kg, and 78.7% capacity retention after 9800 cycles. In addition, TiSi₂ nanonet itself is found to be a good anode material due to the special layer-structure of C49 crystals. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Leung Yee Pan = 利用有機金屬化學氣相沉積方法生長一維硒化鋅鈉米結構 / 梁懿斌. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 80-82). / Text in English; abstracts in English and Chinese. / Leung Yee Pan = li yong you ji jin shu hua xue qi xiang chen ji fang fa sheng chang yi wei xi hua xin na mi jie gou / Liang Yibin. / Acknowledgements --- p.ii / Abstract --- p.iii / Chapter Chapter 1 - --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Motivation --- p.3 / Chapter 1.2.1 --- ZnSe --- p.3 / Chapter 1.2.2 --- MOCVD --- p.3 / Chapter 1.3 --- Our Work --- p.4 / Chapter Chapter 2 - --- Experiment --- p.5 / Chapter 2.1 --- MOCVD System --- p.5 / Chapter 2.2 --- Metalorganic Sources --- p.5 / Chapter 2.3 --- Substrates --- p.7 / Chapter 2.4 --- Substrate Preparations --- p.7 / Chapter 2.5 --- Preheating (Applied Only when Using GaAs Substrates) --- p.7 / Chapter 2.6 --- Growth of Epi-layer (Applied Only when Using GaAs Substrates) --- p.8 / Chapter 2.7 --- Growth of ZnSe Nanowires on Si(100) and ZnSe/GaAs(100) --- p.8 / Chapter 2.8 --- The Samples --- p.9 / Chapter Chapter 3 - --- Characterization --- p.10 / Chapter 3.1 --- Surface Morphologies --- p.10 / Chapter 3.1.1 --- Scanning Electron Microscopy --- p.10 / Chapter 3.1.2 --- Atomic Force Microscopy --- p.12 / Chapter 3.2 --- Structural Properties - X-Ray Diffraction --- p.13 / Chapter 3.3 --- Optical Properties - Photoluminescence --- p.15 / Chapter 3.4 --- Other Techniques --- p.16 / Chapter Chapter 4 - --- Results --- p.17 / Chapter 4.1 --- ZnSe Nanowires Grown on Si(100) --- p.17 / Chapter 4.1.1 --- Effect of Growth Temperature --- p.17 / Chapter 4.2 --- Growth of ZnSe Nanowires on GaAs( 100) - The First Trial --- p.20 / Chapter 4.3 --- Optimizing the ZnSe Epi-layer --- p.21 / Chapter 4.3.1 --- Surface of GaAs(100) --- p.21 / Chapter 4.3.2 --- ZnSe Epi-layer Grown at Different Reactor Pressures --- p.22 / Chapter 4.4 --- Importance of Au --- p.26 / Chapter 4.5 --- Growth of ZnSe Nanowires on GaAs(lOO) - A Systematic Study --- p.28 / Chapter 4.5.1 --- Growth Rates --- p.28 / Chapter 4.5.2 --- Overall Morphologies --- p.32 / Chapter 4.5.3 --- Classifying the Morphologies --- p.37 / Chapter 4.5.4 --- Abundances of Different Morphologies of Different Samples --- p.40 / Chapter 4.5.5 --- Growth Direction --- p.45 / Chapter 4.5.6 --- Structure of the Nanowires --- p.50 / Chapter 4.5.7 --- Optical Properties of the Nanowires --- p.54 / Chapter Chapter 5 - --- Discussions --- p.57 / Chapter 5.1 --- Overview of the MOCVD Process --- p.57 / Chapter 5.1.1 --- Effects of Growth Temperature on Growth Rate of MOCVD --- p.58 / Chapter 5.1.2 --- Effects of Reactor Pressure on Growth Rate of MOCVD --- p.59 / Chapter 5.2 --- Effect of Reactor Pressure on the Growth Rate of the Nanowires --- p.60 / Chapter 5.3 --- Growth Mechanisms of the Nanowires --- p.64 / Chapter 5.3.1 --- VLS Mechanism --- p.64 / Chapter 5.3.2 --- Spiral Growth Mechanism --- p.66 / Chapter 5.3.3 --- Reentrant Corner Mechanism --- p.67 / Chapter 5.3.4 --- Roles of Au Particles and ZnSe Epi-layer --- p.68 / Chapter 5.3.5 --- Growth Mechanisms of Different Types of Nanowires --- p.69 / Chapter 5.3.6 --- Effect of Growth Temperature --- p.71 / Chapter 5.4 --- Quality of the Nanowires --- p.72 / Chapter 5.5 --- "Remarks of the AFM Experiments and the ""Transferred"" Samples" --- p.72 / Chapter Chapter 6 - --- Conclusions --- p.75 / Appendices --- p.77 / Chapter I - --- "Estimation of the mass, other than the nanowires, contributed to the sample" --- p.77 / Chapter II - --- Calculation of the growth angle with respect to the surface normal --- p.78 / References --- p.80