New methods to fabricate nanometer sized structures will be a major driving force in transforming nanoscience to nanotechnology. There are numerous examples of the incorporation of nanoscale structures or materials enhancing the functionality of a device. Graphitic carbon is a widely used material in electroanalysis due to a number of advantageous properties such as wide potential window, low cost, mechanical stability, and applicability to many common redox systems. In this thesis, the fabrication of nanometer sized graphitic carbon structures is described. These structures were fabricated by using a combination of electron-beam lithography (EBL) and pyrolysis. EBL allows for the precise control of shape, size and location of these carbon nanostructures. The structure and electrochemical reactivity of thin films of the pyrolyzed material is initially examined. The methodology to fabricate nanosized carbon structures and the structural and electrical characterization of the nanostructure is presented. The nanometer sized carbon structures fabricated in this work are being applied as nanoelectrodes. For nanoband structures, we observe a limiting current plateau which is characteristic of radial diffusion to cylindrical ultramicroelectrodes. Their voltammetric behaviour shows good agreement with classical theoretical predictions. Both carbon film and nanoband electrodes have been used as substrates for metal electrodeposition. The size and morphology of the deposited Au particles depends greatly on the substrate. On the nanoband electrodes, the Au particles exhibit a multi-branched or dendridic morphology. Their size and surface area are much larger than those electrodeposited on the carbon film electrode under the same conditions. The surface enhanced Raman spectroscopy (SERS) properties of the gold deposited on the nanobands was studied. A high enhancement in Raman intensity for a molecular layer on the nanoband supported gold is observed.

Nanoscale science and technology demand novel approaches and new knowledge to further advance. Nanoscale fabrication has been widely employed in both modern science and engineering. Micro/nano lithography is the most common technique to deposit nanostructures. Fundamental research is also being conducted to investigate structural, physical and chemical properties of the nanostructures. This research contributes fundamental understanding in surface science through development of a new methodology. Doing so, experimental approaches combined with energy analysis were carried out. A delicate hardware system was designed and constructed to realize the nanometer scale lithography. We developed a complete process, namely laser-assisted scanning probe alloying nanolithography (LASPAN), to fabricate well-defined nanostructures in gold-silicon (Au-Si) system. As a result, four aspects of nanostructures were made through different experimental trials. A non-equilibrium phase (AuSi3) was discovered, along with a non-equilibrium phase diagram. Energy dissipation and mechanism of nanocrystalization in the process have been extensively discussed. The mechanical energy input and laser radiation induced thermal energy input were estimated. An energy model was derived to represent the whole process of LASPAN.

Interest in the fabrication of nano-optical structures has increased dramatically in recent years, due to advances in lithographic resolution. In particular, metallic nanostructures are of interest because of their ability to concentrate light to well below the diffraction limit. Such structures have many potential applications, including nanoscale photonics, quantum information processing and single molecule detection/imaging. In the case of quantum computing and quantum communication, plasmon-based metal nanostructures offer the promise of scalable devices. This is because the small optical mode volumes of such structures give the large atom-photon coupling needed to interface solid-state quantum bits (qubits) to photons. The main focus of this dissertation is on fabrication and testing of surface plasmon-based metal nanostructures that can be used as optical wires for effciently collecting and directing an isolated atom or molecule's emission. In this work, Ag waveguides having 100nm£50nm and 50nm£50nm cross sections have been fabricated ranging from 5¹m to 16¹m in length. Different types of coupling structures have also been fabricated to allow in-coupling and out-coupling of free space light into and out of the nanometric waveguides. The design of waveguides and couplers have been accomplished using a commercial finite difference in time domain (FDTD) software. Different nanofabrication techniques and methods have been investigated leading to robust and reliable process conditions suitable for very high aspect ratio fabrication of metal structures. Detailed testing and characterization of the plasmon based metal waveguides and couplers have also been carried out. Test results have revealed effective surface plasmon propagation range. 0.5dB/¹m and 0.07dB/¹m transmission losses have been found for 100nm and 50nm wide waveguides respectively, which correspond to 1/e propagation lengths of 9¹m and 60¹m. Input coupling effciency was found to be 2% and output coupling effciency was found to be 35%. The fabrication and testing results presented provide critical demonstrations to establish the feasibility of nanophotonic integrated circuits, scalable quantum information processing devices, as well as other devices, such as single molecule detectors and imaging systems.

Nanoscale science and technology demand novel approaches and new knowledge to further advance. Nanoscale fabrication has been widely employed in both modern science and engineering. Micro/nano lithography is the most common technique to deposit nanostructures. Fundamental research is also being conducted to investigate structural, physical and chemical properties of the nanostructures. This research contributes fundamental understanding in surface science through development of a new methodology. Doing so, experimental approaches combined with energy analysis were carried out. A delicate hardware system was designed and constructed to realize the nanometer scale lithography. We developed a complete process, namely laser-assisted scanning probe alloying nanolithography (LASPAN), to fabricate well-defined nanostructures in gold-silicon (Au-Si) system. As a result, four aspects of nanostructures were made through different experimental trials. A non-equilibrium phase (AuSi3) was discovered, along with a non-equilibrium phase diagram. Energy dissipation and mechanism of nanocrystalization in the process have been extensively discussed. The mechanical energy input and laser radiation induced thermal energy input were estimated. An energy model was derived to represent the whole process of LASPAN.

This study investigates sub 200nm half-pitch polymer structures by nanoimprint process. The trench structures were fabricated on quartz glass with various depths and widths by FIB. To investigate the best nanoimprint process on SU-8, we studied various parameters such as: imprinting temperature, imprinting pressure, and temperature for de-molding, etc. ¡@This study had successfully defined 50nm width with different depths on to SU-8 by imprint. ¡@Imprint temperature above Tg 30¢J with constant pressure on continuous impressing and de-mold in room temperature would result in better imprinting results. The filling rate of this nanoimprint technology was measured by atomic force microscopy. ¡@For structures above/near 100nm half-pitch, the filling rate is nearly 100%.

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Ubiquitous concerns in device fabrication are nanoscale positioning and the integration of complex combinations of diverse materials, many of which are extremely fragile. Frequently the completed device requires one or more of the constituent materials to be synthesized under suboptimal conditions, thus compromising the performance of the final structure. We have developed a platform to fabricate multi-component electrode cross-bar structures, where each material can be synthesized under its own ideal conditions. Furthermore, surface treatments and procedures that may otherwise be incompatible can be performed without concern of damage to the other constituent materials. We demonstrate our approach by fabricating an all carbon cross-bar electrode structure comprised of a graphene-graphite heterojunction. Initially, a graphene field effect transistor is fabricated using electron beam and optical lithography. The top graphite electrode is sculpted from a bulk piece of highly oriented pyrolytic graphite with the aid of a focused ion beam (FIB) and integrated micromanipulator system. This requires real-time shaping, cutting, accurate positioning (circa 100 nm precision) and wiring of the graphite top electrode. Electron transport characteristics of each electrode component and the final heterostructure have been measured. We show that this process is effective for the production of micron and submicron-scale multi-layer device structures including other materials such as gold. This fabrication scheme could be extended to produce novel structures such as mechanical resonators, and provide a foundation for combining fragile materials that have otherwise been incompatible with traditional fabrication techniques. / Graduate

The field of plasmonics has offered the promise to combine electronics and photonics at the nanometer scale for ultrafast information processing speeds and compact integration of devices. Various plasmonic waveguide schemes were proposed with the potential to achieve switching functionalities and densely integrated circuits using optical signals instead of electrons. Among these, the hybrid plasmonic waveguide stands out thanks to two sought-out properties: long propagation lengths and strong modal confinement. In this work, hybrid plasmonic waveguides and passive devices were theoretically investigated and experimentally demonstrated on an integrated silicon platform. A thin SiO2 gap between a gold conductive layer and a silicon core provides subwavelength confinement of light inside the gap. A long propagation length of 40µm was experimentally measured. A system of taper coupler connects the plasmonic waveguide to conventional photonic waveguides at a high efficiency of 80%. Passive devices were also fabricated and characterized, including S-bends and Y-splitters. / Microsystems and Nanodevices

Micro-electromechanical systems (MEMS) are electrically controlled micro-machines which have been widely used in both industrial applications and scientific research. This technology allows us to use macro-machines to build micro-machines (MEMS) and then use micro-machines to fabricate even smaller structures, namely nano-structures. In this thesis, the concept of Fab on a Chip will be discussed where we construct a palette of MEMS-based micron scale tools including lithography tools, novel atomic deposition sources, atomic mass sensors, thermometers, heaters, shutters and interconnect technologies that allow us to precisely fabricate nanoscale structures and conduct in-situ measurements using these micron scale devices. Such MEMS devices form a novel microscopic nanofabrication system that can be integrated into a single silicon chip. Due to the small dimension of MEMS, fabrication specifications including heat generation, patterning resolution and film deposition precision outperform traditional fabrication in many ways. It will be shown that one gains many advantages by doing nano-lithography and physical vapor deposition at the micron scale. As an application, I will showcase the power of the technique by discussing how we use Fab on a Chip to conduct quench condensation of superconducting Pb thin films where we are able to gently place atoms upon a surface, creating a uniform, disordered amorphous film and precisely tune the superconducting properties. This shows how the new set of techniques for nanofabrication will open up an unexplored regime for the study of the physics of devices and structures with small numbers of atoms.