In this thesis, we study a series of Si-doped GaN thin films and nanodots. These samples are growth on c-face sapphire substrate by Molecular Beam Epitaxy. In Si-doped GaN thin film growth, different Si cell temperature are used to control the dopant concentration. Van der Pauw hall measurement is used to measure the carrier concentrations and the mobilities. As increase Si cell temperature, the carrier concentration and the mobility increase. The maximum carrier concentration is 8 ¡Ñ 1019 cm-3, and the maximum mobility is 194 cm2/V-s. As increasing the Si dopant concentration, the near band edge photoluminescence emission peak intensity increases, but the full width at half maximum broaden from 47 meV to 117 meV. In Raman measurement result, with the increasing of Si dopant concentration, the E2(high) mode shifts from 569.4 cm-1 to 567.9 cm-1. The A1(LO) mode disappears gradually. In the nanodot growth, the AFM images show that the nanodots size become large as increasing the growth time. The nanodots size is change from 1.2 nm to 5.6 nm high and 40 nm to 110 nm wide, but the density of the nanodots decreases from 1.9 ¡Ñ 1010 cm-2 to 6 ¡Ñ 109 cm-2 at 15 sec and 90 sec growth, respectively. According to the AFM image of the nanodots surface morphology, the nanodots growth mode should be the Stranski-Krastanow mode.

The image resolution of atomic force microscopy (AFM) is still less superior to that of the electron microscopy (EM). However AFM operated in liquids complemented by Tapping-mode (TM) detection proves to be more suitable for imaging biomolecules in physiological-like environments. Nevertheless, manipulation of AFM in solution turned out to be non-trivial, several technical difficulties were encountered. In the thesis, I report using divalent cation-containing buffer as a feasible method to immobilize DNA molecules effectively for imaging in liquid media. AFM operating conditions, such as cantilever oscillating drive frequency, setpoint amplitude, feedback control parameters and scan rates were studied to obtain the optimized function. Various AFM images of Ssp I-linearized pUC19 DNA/EcoR I restriction enzyme complexes were captured, revealing the molecular details of their complex machineries. For example, the intermediate stage of the enzyme cleavage action was displayed by images showing that DNA was bent by an acute angle at the active site in the presence of one single EcoR I molecule. Some evidence for a jumping, sliding or intersegmental transfer mechanism is achieved. To trace the enzyme-DNA interaction dynamic in real time, preliminary results were obtained, but further improvements are required.

This study is focused on the technique for fabrication of high aspect ratio nanostructures by combining both the advantages of maskless patterning of focused ion beam (FIB) and anisotropic etching of inductively coupled plasma etcher (ICP) in CF4 atmosphere. The materials contain p-type (100) single crystal silicon and thermal silicon dioxide. The study details include¡G (1) The reliability of AFM when scanning isotropic and anisotropic nanostructures with high aspect ratio tip in tapping mode. (2) FIB direct writing test. (3) The influences of ICP parameters including ICP power, bias power, content of oxygen, and process pressure. After completion of above-mentioned items, an optimized condition is used to get the anisotropic Si-based high aspect ratio nanostructures of holes array, gratings and cylinder under 100nm. The smallest line width of single crystal silicon gratings is 48nm, and aspect ratio up to 2.36. The smallest line width of silicon dioxide gratings is about 100nm, height is 410nm and aspect ratio up to 2.36 measured by SEM. By combining both advantages of different systems, we can provide another simple and rapid method for nanofabrication.

Growth and dissolution of the mineral calcite is important for prediction and control of surface and subsurface water quality, calculation of past sea-surface temperatures using paleoenvironmental proxies, and sequestration of contaminants through engineered calcite precipitation. At high concentrations of strontium, calcite growth is known to be inhibited, but the mechanism by which strontium inhibits growth is not well understood. Seeking to better understand this mechanism, atomic force microscopy is used with a flow-through fluid cell to measure real time growth rates of the obtuse and acute monomolecular step orientations on the calcite surface. Growth was measured at two saturation indices as a function of the ratio of the concentrations of aqueous calcium-to-carbonate and varying aqueous strontium concentration. It was found that the amount of strontium required to inhibit growth correlated with the aqueous calcium concentration, but did not correlate with carbonate concentration. This suggests that strontium inhibits attachment of calcium, but not carbonate, during growth. Analytical models of nucleation and propagation of steps are expanded from previous studies to capture multiple saturation indices.

No description available.

Organic photovoltaics (OPVs) offer the prospect of inexpensive processing compared with conventional crystalline semiconductor cells. These cells are still lower in efficiency than their inorganic counterparts, in part because a detailed understanding of the role that interfaces play in these devices is lacking. The electronic properties of the surface of the common transparent electrode Indium:Tin Oxide (ITO) have been studied both on a macroscopic and nanoscopic scale, and the interface between ITO and organic materials has been studied on a macroscopic scale as well. Little work has been done on the nanoscopic properties of the ITO/organic interface. This dissertation introduces a new conducting-probe atomic force microscope (CP-AFM) technique, Scanning Current Spectroscopy (SCS), for probing the nanoscopic lateral variation in the electronic properties of this interface, and demonstrates its utility by examining the ITO/copperphthalocyanine (CuPc) interface. SCS demonstrates large lateral variations in the hole collection efficiency at that interface on a nanometer length scale, and that the distribution of these variations is affected by ITO pretreatment. Measurements on OPVs demonstrate that the performance of these devices is dependant on the nanoscopic lateral variation in surface properties that SCS measures, and that in the case of the ITO/CuPcinterface SCS explains the observed device behavior better than techniques that yield macroscopic average electronic properties, such as photoelectron spectroscopy. Additionally, this dissertation discusses advances made in the design of an integrated optical refractive index sensor. The sensor uses organic light-emitting diodes (OLEDs) and OPVs as integrated light-sources and detectors on top of a slab waveguide substrate. The platform offers potentially high sensitivities to refractive index changes (and the selective binding of chemical and biological analytes), and is amenable to largescale integration for on-chip multiplexed detection. The refractive index response has been demonstrated previously, but the performance was limited by electrical noise and OLED drift. The use of different absorbing species in the OPV, integration of multiplesensors on a single substrate, addition of a reference channel to monitor OLED drift andthe use of lock-in amplification for signal processing allow the sensor to detect changesof 10-4 refractive index units.

In this thesis we describe two separate experiments involving the use of gold nanoparticles. The first experiment looks at the use of gold nanoparticles as a localized heat source and the potential application as a cancer treatment. The second experiment, which is the real focus of this thesis, applies gold nanoparticles in the study of the free surface dynamics of glassy thin films. Gold nanoparticles have the ability to strongly absorb the energy in an incident laser beam and convert that energy into heat. Photothermal therapy is a proposed cancer treatment which exploits this ability to irreparably damage cancerous tissues surrounding gold nanoparticles. In the first chapter of this thesis we explain an experiment designed to probe the local temperatures achieved in such a process. Gold nanoparticles are used to stabilize the boundary of an inverse micelle system which contains an aqueous fluorescent dye solution on it's interior. A temperature dependent fluorescence intensity allows us to probe the temperature changes induced by laser irradiation. In the remainder of this thesis we describe a separate experiment involving the use of gold nanoparticles to study the free surface dynamics of thin glassy films. There is a growing body of evidence in the literature that thin polymer films in the glassy state exhibit heterogeneous dynamics; specifically that the first few nanometers from an air-polymer interface exhibit enhanced mobility relative to the interior of the film. The underlying mechanism responsible for this enhanced mobility remains elusive, however some believe it to be a direct consequence of the polymeric nature of these films. We describe in detail an experiment aimed at addressing this concern. We deposit gold nanoparticles onto the surface of a molecular (non-polymeric) glassy film and monitor their behaviour upon heating using atomic force microscopy. Our results clearly show the existence of enhanced surface mobility in the system studied and provide strong evidence that enhanced surface mobility should be expected in all glass forming systems.

Marine biofouling is the accumulation of marine species on surfaces submerged in seawater leading to unwanted problems for man-made surfaces such as hulls of ships and aquaculture nets. Historically, the amount of biofouling was regulated using metal based coatings whose usage have been disused lately due to adverse toxic effects. Alternative environmentally friendly coatings are currently avidly being pursued. Nanopatterned polymer thin films were investigated as potential candidates for marine antifouling coatings. Polystyrene-block-poly(2-vinyl pyridine) and polystyrene-block-poly(methyl methacrylate) diblock copolymer thin films self-assembled using vapor solvent annealing into cylinders perpendicular to the substrate composed of poly(2-vinyl pyridine) or poly(methyl methacrylate) respectively with diameters between 30 nm to 82 nm and center-to-center spacing between 46 nm to 113 nm in a polystyrene matrix on various substrates such as silicon or nylon. Polystyrene-block-poly(2-vinyl pyridine) copolymers were also mixed with the photoinitiator benzophenone and irradiated with ultraviolet light to crosslink the polymer chains and decrease the surface hydrophobicity. In the case of polystyrene-block-poly(methyl methacrylate), the yield of these nanopatterned films increased with the modification of the vapor annealing method. A low temperature vapor annealing technique was developed in which the annealing occurs at 2 °C. In another strategy, polystyrene and poly(2-vinyl pyridine) homopolymers were nanopatterned with alternating lines and grooves with widths between 200 nm and 900 nm and depths between 15 nm to 100 nm using Thermal Nanoimprint Lithography. Poly(2-vinyl pyridine) films were synthesized as brushes using surface initiated Atom Transfer Radical Polymerization to produce robust polymer films. The chemical and/or the topographical heterogeneity of the polymer surfaces influenced the settlement of Ulva linza algae zoospores. Overall, the incorporation of nanoscale features enhanced the antifouling properties of the samples. Further exploration of these types of coatings is highly encouraged.

Marine biofouling is the accumulation of marine species on surfaces submerged in seawater leading to unwanted problems for man-made surfaces such as hulls of ships and aquaculture nets. Historically, the amount of biofouling was regulated using metal based coatings whose usage have been disused lately due to adverse toxic effects. Alternative environmentally friendly coatings are currently avidly being pursued. Nanopatterned polymer thin films were investigated as potential candidates for marine antifouling coatings. Polystyrene-block-poly(2-vinyl pyridine) and polystyrene-block-poly(methyl methacrylate) diblock copolymer thin films self-assembled using vapor solvent annealing into cylinders perpendicular to the substrate composed of poly(2-vinyl pyridine) or poly(methyl methacrylate) respectively with diameters between 30 nm to 82 nm and center-to-center spacing between 46 nm to 113 nm in a polystyrene matrix on various substrates such as silicon or nylon. Polystyrene-block-poly(2-vinyl pyridine) copolymers were also mixed with the photoinitiator benzophenone and irradiated with ultraviolet light to crosslink the polymer chains and decrease the surface hydrophobicity. In the case of polystyrene-block-poly(methyl methacrylate), the yield of these nanopatterned films increased with the modification of the vapor annealing method. A low temperature vapor annealing technique was developed in which the annealing occurs at 2 °C. In another strategy, polystyrene and poly(2-vinyl pyridine) homopolymers were nanopatterned with alternating lines and grooves with widths between 200 nm and 900 nm and depths between 15 nm to 100 nm using Thermal Nanoimprint Lithography. Poly(2-vinyl pyridine) films were synthesized as brushes using surface initiated Atom Transfer Radical Polymerization to produce robust polymer films. The chemical and/or the topographical heterogeneity of the polymer surfaces influenced the settlement of Ulva linza algae zoospores. Overall, the incorporation of nanoscale features enhanced the antifouling properties of the samples. Further exploration of these types of coatings is highly encouraged.

No description available.