A new type Rayleigh scattering of Mössbauer radiation (RSMR) spectrometer was developed, which due to favorable time scale of scattering process is suitable for the studies of complicated dynamics of biomolecules (not containing mössbauer nucleus) Densely packed iron nanowire arrays were created using template method of aluminum anodic oxide (AAO). Pore size and density of AAO template can be easily controlled by adjusting anodizing conditions. Shape and diameter of nanowires appear to be exact replicas of AAO pores. the effectiveness of different aqueous electrolytes used in nanowire deposition was investigated. Growth rate in different electrolytes was determined to be 52±2 nm/min. and 11,8±0,6 nm/min. This study has demonstrated the effects of aging of iron nanowires embedded within the pores of the AAO template. the influence of annealing parameters on the chemical composition of iron nanowires was investigated. CEMS studies have revealed. / Panaudojus puslaidininkinį γ-kvantų detektorių sukurtas naujo tipo Mesbauerio spinduliuotės Relėjaus sklaidos spektrometras, kuris dėl tinkamo γ-kvantų sklaidos laiko gali būti taikomas konformacinių judesių biologiniuose objektuose ir polimeruose, neturinčiuose mesbauerinių branduolių, tyrimams. Paruošti geležies nanosiūlų kolonijos, esančias aliuminio anodinio oksido (AAO) matricoje. Parenkant anodavimo sąlygas galima kontroliuoti, susidariusio tvarkingo porėto AAO, porų dydį ir tankį. Pagamintos AAO matricos užpildytos geležimi, taip susiformuoja žinomo dydžio nanosiūlai, kurių diametras atitinka porų diametrą. Palygintas vandeninių elektrolitų, skirtų užpildyti AAO poras, efektyvumas. Augimo greitis skirtinguose elektrolituose yra 52 ± 2 nm/min. ir 11,8 ± 0,6 nm/min. Nustatyti geležies nanosiūlų cheminės sudėties pokyčiai susidarymo ir senėjimo metu. Eksperimentiniais tyrimais įrodyta, kad geležies nanosiūlai AAO matricoje oksiduojasi ne visu tūriu, bet nuo atvirojo galo. Pakaitinus (daugiau nei 200 °C) metalinius nanosiūlus įkalintus AAO matricose, šie reaguoja su anodinio aliuminio oksidu ir sudaro špinelines struktūras.

Nanotechnology is an emerging inter-disciplinary paradigm which encompasses diverse fields of science and engineering converge at the nanoscale. This nanoscale science and nanostructure engineering have well demonstrated in the fabrication of sensors/transducers devices with faster response time and better sensitivity then the planer version of the sensor’s configurations. Nanotechnology is not just to grow/fabricate nanostructures by just mixing nanoscale materials together but it requires the ability to understand and to precisely manipulate and control of the developed nanomaterials in a useful way. Nanotechnology is aiding to substantially improve, even revolutionize, many technology and industry sectors like information technology, energy, environmental science, medicine/medical instrumentation, homeland security, food safety, and transportation, among many others. Such applications of nanotechnology are delivering in both expected and unexpected ways on nanotechnology’s promise to benefit the society. The semiconductor ZnO with wide band gap (~ 3.37 eV) is a distinguish and unique material and its nanostructures have attracted great attention among the researchers due to its peculiar properties such as large exciton binding energy (60 meV) at room temperature, the high electron mobility, high thermal conductivity, good transparency and easiness of fabricating it in the different type of nanostructures. Based on all these fascinating properties, ZnO have been chosen as a suitable material for the fabrication of photonic, transducers/sensors, piezoelectric, transparent and spin electronics devices etc. The objective of the current study is to highlight the recent developments in materials and techniques for electrochemical sensing and hetrostructure light emitting diodes (LEDs) luminescence properties based on the different ZnO nanostructures. The sensor devices fabricated and characterized in the work were applied to determine and monitor the real changes of the chemical or biochemical species. We have successfully demonstrated the application of our fabricated devices as primary transducers/sensors for the determination of extracellular glucose and the glucose inside the human fat cells and frog cells using the potentiometric technique. Moreover, the fabricated ZnO based nanosensors have also been applied for the selective determination of uric acid, urea and metal ions successfully. This thesis relates specifically to zinc oxide nanostructure based electrochemical sensors and photonic device (LED) applications.

A new class of electrodes with nanometer-scale contact spacing can be produced at the edge of patterned metal/insulator/metal this film structures. A key challenge is to produce insulator layers with low leakage current and have pristine metal contacts for controlled molecular contacts. Atomic layer deposition of high quality Al2O3 thin films onto Au electrodes was enabled by surface modification with a self-assembled monolayer of -OH groups that react with a monolayer of trimethylaluminum gas source. Ar ion milling was then used to expose the edge of the Au/dielectric/Au structure for molecular electrode contacts. The junctions are characterized by atomic force microscope and tunnel current properties. The Au/self-assembled monolayer/Al2O3/Au tunnel junction, with a very thin oxide insulator layer (15.4 Å), is stable and has a small tunneling current density of about 0.20 ~ 0.75 A/cm2 at 0.5 V. Organometalic cluster molecules were attached to bridge the electrodes. Through tunnel current modeling, low temperature and photo current measurements, molecular current was found to be consistent with direct tunneling through the organic tethers to available states at the metal center. This novel electrode was also used to study the efficiency of organic conducting thin films where the photovoltaic efficiency can be improved when the electrode separation distance is below the exciton diffusion length. Copper (II) phthalocyanine (CuPc) was thermally evaporated between the nano-gap electrodes formed by Au/Al2O3/Au tunnel junctions. A large photocurrent enhancement over 50 times that of bulk CuPc film was observed when the electrode gap distance approached 10 nm. CuPc diffusion length is seen to be 10 nm consistent with literature reports. All devices show diode I-V properties due to a large Schottky barrier contact resistance between the small top Au electrode and the CuPc film. To add another dimension of nm-scale patterning, nanowires can be used as line-of-sight shadowmasks provided that nanowire location and diameter can be controlled. Lateral ZnO nanowires were selectively grown from the edge of a Si/Al2O3/Si multi-layer structure for potential integration into devices utilizing Si processing technology. Microstructural studies demonstrate a 2-step growth process in which the tip region, with a diameter ~ 10 nm, rapidly grew from the Al2O3 surface. Later a base growth with a diameter ~ 22 nm overgrew the existing narrow ZnO nanowire halting further tip growth. Kinetics studies showed surface diffusion on the alumina seed surface determined ZnO nanowire growth rate.

A versatile AFM local oxidation lithography was developed for fabricating clean protein patterns ranging from nanometer to sub-millimeter scale on octadecyltrichlorosilane (OTS) layer of Si (100) wafer. This protein patterning method can generate bio-active protein pattern with a clean background without the need of the anti-fouling the surface or repetitive rinsing. As a model system, lysozyme protein patterns were investigated through their binding reactions with antibodies and aptamers by AFM. Polyclonal anti-lysozyme antibodies and anti-lysozyme aptamer are found to preferentially bind to the lysozyme molecules on the edge of a protein pattern before their binding to the interior ones. It was also demonstrated that the topography of the immobilized protein pattern affects the antibody binding direction. We found that the anti-lysozyme antibodies binding to the edge lysozyme molecules on the half-buried pattern started from the top but the binding on the extruded pattern started from the side because of their different spatial accessibility. In addition, after incubating lysozyme pattern with anti-lysozyme aptamer in buffer solution for enough long time, some fractal-shaped aptamer fibers with 1-6nm high and up to tens of micrometers long were formed by the self-assembling of aptamer molecules on the surface. The aptamer fibers anchor specifically on the edge of protein patterns, which originates from the biospecific recognition between the aptamer and its target protein. Once these edge-bound fibers have formed, they can serve as scaffolds for further assembly processes. We used these aptamer fibers as templates to fabricate palladium and streptavidin nanowires, which anchored on the pattern edges and never cross over or collapse over each other. The aptamer fiber scaffold potentially can lead to an effective means to fabricate and interface nanowires to existing surface patterns.

This work focuses on a simple template assisted approach for fabricating I-III-VI semiconductor nanowire arrays. Vertically aligned nanowires of p-CIS of controllable diameter and thickness are electrodeposited, from an acidic electrolyte solution, inside porous aluminum templates using a three electrode set up with saturated calomel electrode as the reference. AAO template over ITO-glass was used as starting template for the device fabrication. The deposited CIS is annealed at different temperatures in a reducing environment (95% Ar+ 5% H2) for 30 minutes. X-ray diffraction of the nanowires showed nanocrystalline cubic phase structures with a strong orientation in the <112> direction. The effective bandgap of the deposited CIS nanowires determined using the Near Infrared (NIR) Spectrometer was found to be 1.07eV. The type of CIS electrodeposited inside the porous alumina template is determined to be p-type from the Schottky diode obtained with ITO-CIS-Au structure. Schottky diodes were characterized and analyzed at room temperature.

Vertically aligned nanowire arrays of copper phthalocyanine (CuPc) and CuPc-Al Schottky diodes, of controllable diameter and length were fabricated by cathodic electrodeposition of CuPc into anodized alumina (AAO) templates, followed by annealing at 300 ºC in Argon. AAO over Aluminum tape and that over ITO-glass were both used as starting templates for the device fabrication. Depending on the dimensions of the starting AAO template, diameters of CuPc nanowires ranged from 30 nm to 40 nm and the lengths ranged from 500 nm to 1 μm. The temperature dependence of the phase and the absorption spectrum of the nanowires are reported. The electrodeposited nanowires (as prepared) had the preferred crystallite orientation of the α-phase. ITO formed the ohmic contact and Schottky contacts were formed between CuPc and aluminum. Insertion of a thin layer of PEDOT:PSS between CuPc nanowires and the ITO electrode improved the contact and reduced the series resistance by an order of magnitude. Schottky diodes were characterized and analyzed at room temperature and at cryogenic temperatures.

This work focuses on the growth of vertically aligned CdTe nanowire arrays of controllable diameter and length using cathodic electro deposition in anodized alumina templates. This step was followed by annealing at 250° C in a reducing environment (95% Ar + 5% H2). AAO template over ITO-glass was used as starting template for the device fabrication. The deposited nanowires showed nanocrystalline cubic phase structures with a strong preference in [111] direction. First gold (Au) was deposited into AAO using cathodic electro deposition. This was followed by CdTe deposition into the pore. Gold was deposited first as it aids the growth of CdTe inside AAO and it makes Schottky contact with the deposited n type CdTe. CdTe was determined to be n-type from the fact that back to back diode was obtained with Au-CdTe-Au test structure. Aluminum (Al) was sputtered on the top to make the ohmic contact to the n type CdTe deposited in AAO. Analysis of Schottky diodes yielded a diode ideality factor of 10.03 under dark and 10.08 under light and reverse saturation current density of 34.9μA/cm2 under dark and 39.7μA/cm2 under light.

Nanowires are high aspect ratio nanostructures with structural diameters on the order of nanometers to hundreds of nanometers. In this work, the optical properties of highly crystalline silicon nanowires grown by the Vapor-Liquid-Solid (VLS) method surrounded by a thin silicon shell are investigated for thin film solar cell applications. Crystalline core nanowires were surrounded by a conformal amorphous silicon shell and exhibited extremely high absorption of 95% at short wavelengths (??<550nm) and very low absorption of <2% at long wavelengths (??>780nm). Nanowires were disordered with average lengths ranging from 1.3 to 2.3 ??m. The absorption increased at longer wavelengths as a function of amorphous shell radial thickness, significantly higher than the absorption of a reference planar a-Si thin film. In addition, a new method to grow epitaxial silicon at low growth temperatures on glass substrates is demonstrated. Highly crystalline silicon nanowires with an average length of 800 nm were used as the seed crystal to grow an epitaxial silicon shell around, using a low temperature process. The nanowire core was grown at 400??C, and the shell was grown at about 150??C. Such epitaxial grown nanowire shells could be used as a building block for nanotechnology applications in which epitaxial silicon is required over large-area substrates such as glass. Furthermore, the epitaxial silicon shell nanowires exhibited absorption > 90% up to a wavelength of 600 nm, which was significantly higher than that of a planar 1 ??m nanocrystalline silicon film. The high absorption exhibited by nanowires with both amorphous and crystalline silicon shells makes them promising for use in photovoltaic and photodetector applications. Silicon nanowires were incorporated into thin film silicon n-i-p solar cells in two configurations: as a nanostructured back reflector, and in core-shell nanowire solar cells. First, domed-shaped nanostructures were fabricated by coating an array of silicon nanowires with a thick layer of amorphous silicon. After the nanostructures were coated with Ag and ZnO:Al, they were used as the backreflector in an n-i-p amorphous silicon solar cell. The nanostructured backreflector improved light scattering within the solar cell, leading to a short circuit current of 14.8mA/cm2, a 13% improvement over that of the planar device, which had a Jsc=13.1 mA/cm2. The overall conversion efficiency of nanostructured backreflector device was ?? = 8.87%, a strong improvement over that of the planar device (?? = 7.47%). Silicon nanowires were also incorporated into core-shell nanowire solar cells. The first device architecture investigated consisted of nanowires incorporated as the intrinsic absorption layer between a planar n+ layer and conformal p+ layer. However, the fabricated devices exhibited very low collection efficiencies of < 2% due to the presence of impurities incorporated by the catalyst used during nanowire growth. As a result, the device architecture was modified such that the nanowires provided high aspect ratio structure to enhance absorption in a shell material, but the nanowires themselves were not used as an active device component. Nanowire core-amorphous silicon shell solar cells, on average 525 nm long and about 350nm in total diameter, exhibited an impressive low total reflectance of <3% in the wavelength interval of 410 nm < ?? < 640nm and exceeded 10% only for ??>700 nm. As a result, the core-shell nanowire devices exhibited enhancement in quantum efficiency at low wavelengths, ?? < 500nm and high wavelengths, ?? > 600nm as compared to a planar device. The resulting short circuit current was 14.1 mA/cm2 compared to 12.3 mA/cm2 for the planar device, an improvement of ~15%. Nanowire core- nanocrystalline silicon shell solar cells were also fabricated using the same device architecture. Core-shell nanowires with an average length of 800 nm showed significant enhancement in quantum efficiency over all wavelengths as compared to a 1 ??m thick planar solar cell. The core-shell nanowire device had a short-circuit current of 16.2 mA/cm2 , a ~25% improvement over that of the planar thin film solar cell (Jsc=13.0 mA/cm2). Core-shell nanowire devices did, however, have lower open circuit voltage compared to the planar device. Non-conformal coverage was found to be a limiting factor in device performance, but further improvements can be expected with optimization of the n-i-p deposition conditions and nanowire density.

A self-terminated electrochemical method was used to fabricate microscopic-scale contacts between two Au electrodes in a microfluidic channel. The conductance of contacts varies in a stepwise fashion showing quantization near the integer multiples of the conductance quantum ( ). The mechanism works by a pressure-driven flow parallel to a pair of Au electrodes with a gap on the order of micron in an electrolyte of HCl. When applying a bias voltage between two electrodes, metal atoms are etched off the anode and dissolved into the electrolyte as metal ions, which are then deposited onto the cathode. Consequently, the gap decreases to the atomic scale and then completely closes as the two electrodes form a contact. The electrochemical fabrication approach introduces large variance in the formation and location of individual junctions. Understanding and controlling this process will enable the precise positioning of reproducible geometries into nano-electronic devices.

As CMOS manufacturing technology approaches fundamental limits, researchers are looking for revolutionary technologies beyond the end of the CMOS roadmap. Recent progress on devices, nano-manufacturing, and assembling of nanoscale structures is driving researchers to explore possible new fabrics, circuits and architectures based on nanoscale devices. Several fabric architectures based on various nanoscale devices have been proposed for nanoscale computation. These show great advantages over conventional CMOS technology but focus on FPGA-style applications. There has been no work shown for nanoscale architectures tuned for a processor application. This dissertation proposes a novel nanowire-based 2-D fabric referred to as Nanoscale Application-Specific IC (NASIC). Compared with other nanoscale fabric architectures, NASIC designs can be optimized for higher density and performance in an application-specific way (similar to ASIC in this aspect) and used as a fabric for processors. We present the design of a wire-streaming processor (WISP-0), which exercises many NASIC circuit styles and optimizations. A major goal of NASIC, and for other nanoscale architectures, is to preserve the density advantage of underlying nanodevices. Topological, doping and interconnect constraints can severely impact the effective density that can be achieved at the system level. To handle these constraints, we propose a comprehensive set of optimizations at both circuit and logic levels. Evaluations show that with combined optimizations, WISP-0 is still 39X denser than the equivalent design in 18nm CMOS technology (expected in 2018 by ITRS). Another key challenge for nanoscale computing systems is dealing with the unreliable nanodevices. The defect rate of nanodevices is expected to be orders of magnitude higher than what we are accustomed to with conventional CMOS processing based on lithography. In this dissertation, we first investigate various sources of defects/faults in NASIC circuits and analyze their impacts. Then, a hierarchical, multi-layer solution is proposed to tolerate defects/faults. Simulation shows that the yield of WISP-0 is as high as 50% even if as many as 15% transistors are defective. Estimations of the speed, power consumption of NASIC designs are also presented.