In this thesis, we will discuss how to grow InN nanorods. We have tried different parameters to grow InN nanorods on silicon (111) substrate by plasma assisted molecular beam epitaxy (PAMBE). The growth temperature and V/III ratio are the most important factors in growth. By changing these two factors, we can grow InN into different forms. Another factor of forming InN nanorod is AlN buffer layer. Growing without AlN buffer layer, InN nanorods can be removed from substrate very easily. Growing with AlN buffer layer, the interface between InN nanorods and silicon substrate seems stronger. After a long time growth, the bottoms of InN nonarods combine together. Therefore, the morphology of this sample seems like InN nanorods grown on InN film. From XRD measurement, we can know the InN nanorod is growing alone the c-axis. Without the signal of In metal shows InN nanorod were grown under the N-rich condition. We found that the peak position of PL spectra is about 0.66 eV. And did not have any shift while the temperature changing. Measuring CL spectra of areas with different diameters of single InN nanorod, we got almost the same result. The peak positions are around 0.63 eV. We calculate the quantum size of InN for having quantum effect is about 17 nm. Maybe it is one of the reasons of peak positions did not get shift while diameter changing. In Raman spectra, the E2(high) peak of InN nanorod is 488.23 cm-1, it is closer to the unstrained InN (488 cm-1) than InN film.

The goal of this thesis is to grow InGaN at different temperatures in the form of GaN/InGaN double-heterojunction nanorods. XRD is used to analyze the In composition of film. PL, £g-PL, and CL are used to study the luminescence of InGaN and GaN, and calculation of In composition. For nanorods, the TEM and EDS are the tools to study the In composition and InGaN thickness. SEM is used to study the sample morphology. The work of EL has also been done in this thesis.

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At this study three samples of hematite nanorods were deposited on the silicon substrates with different varieties of glancing angle deposition techniques. One sample (S1) was prepared by using thermal deposition with partially ionized beam (PIB) and substrate rotation. The second sample (S2) was synthesized by using thermal deposition with PIB and no substrate rotation. The third sample (S3) was obtained by using E-beam deposition, PIB and rotating substrate. In addition, one sample of magnetite nanorods (S4) has been prepared in order to compare the magnetic properties of the two different iron oxides. S4 was prepared by using thermal deposition and fixed glancing angle deposition, but no PIB was applied. The hysteresis loop has been studied for all samples and the temperature dependent magnetic properties of one of the hematite samples and the magnetite been studied, too. The studies of the magnetic hysteresis for S1, S2, S3 and S4 showed that all of the samples have hysteresis loops but with dissimilar values of the saturation magnetization Ms, remanence MR, and coercivity HC. Furthermore, the hysteresis loops of all four samples showed different behaviors as the nanorods of the samples change the orientation with respect to the magnetic field. In addition to that fact, the hysteresis loop demonstrated that samples that have similar morphology have like behavior of the hysteresis loop. Also, it has found that S2 has the largest hysteresis loop of all hematite samples and it has large hysteresis loop in the perpendicular and parallel directions with the field as well. However, the magnetite hysteresis loops are significant larger than the ones of the hematite. Likewise, the studies of the temperature dependence magnetic properties of S2 and S4 showed that the ZFC and FC M-T curves of S1and S4 behaved differently when the direction of the nanorods changed from perpendicular to parallel with the field. In addition, the ZFC and FC M-T curves of hematite were different than the ZFC and FC M-T curves of magnetite.

"“One-dimensional” nanostructures like nanotubes and nanorods hold great potential for a wide variety of applications. In particular, one-dimensional nanostructures may be able to provide many significant advantages over traditional spherical particles for drug delivery applications. Recent studies have shown that long, filamentous particles circulate longer within the body than spherical particles, giving them more time to reach the target area and deliver their payload more efficiently. In addition, studies investigating the diffusion of drugs through nanochannels have shown that the drug diffusion profiles can be controlled by varying the nanochannel diameter when the drug diameter and nanochannel diameter are close in size. The combination of increased circulation time and controllable drug release profiles give onedimensional nanostructure great potential for future drug release applications. To fully realize this potential, a simple, low cost, and versatile fabrication method for one-dimensional nanostructures needs to be developed and exploited. The objective of this work is to demonstrate the versatility of template-assisted nanofabrication methods by fabricating a variety of unique protein and polymer one-dimensional nanostructures. This demonstration includes the adaptation of two different template-assisted methods, namely layer-by-layer assembly and template wetting, to fabricate glucose oxidase nanocapsules with both ends sealed, segmented polystyrene and poly(methyl methacrylate) nanorods, and poly(L-lactide)-poly(methyl methacrylate) core-shell nanowires with adjustable shell layer thicknesses. The unique nanostructure morphologies that were achieved using our novel fabrication methods will open the arena for future research focused on process control and optimization for specific applications."

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In this work, Mn atoms are doped into GaN nanorods by two doping types, homogeneous and delta doping, and GaN nanorods are grown on Si (111) substrate using plasma-assisted MBE. The GaMnN nanorods are characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), high-resolution x-ray diffraction (HR-XRD), Raman scattering, Transmission electron microscopy (TEM), superconducting quantum interference device (SQUID), and x-ray photoelectron spectroscopy (XPS). The Mn delta-doping GaN nanorods with Ga/Mn growth time ratio 20 are approximately 1500 nm in height, grown along the c-axis. The Mn concentration in nanorods is determined to be 0.83% by EDS, without secondary phase formation. The Mn atoms substitute Ga sites in the GaN wurtzite hexagonal structure and, according to the results of Raman, there is no observable Mn-N cluster formation existed. The delta-doping structure, without secondary phase inclusions, can be observed under TEM imaging of the nanorods. The nanorods appear to show ferromagnetic behavior at room temperature, as judged by the M-H with hysteresis curve, however the small the loops are. The delta-doping is adopted in this thesis work to fabricate GaMnN DMS nanorods without secondary phase formation.

Nearly dislocation-free vertical GaN pillars in nanoscale were grown on Si (111) surface through self-assembly by molecular-beam epitaxy. No extra catalytic or nanostructural assistance has been employed. These nanorods have a lateral dimension from 10 nm to ~ 800 nm and a height of 50 nm to 3

Coherent injection, detection and manipulation of spins in semiconductor nansotructures can herald a new genre of information processing devices that are extremely energy-efficient and non-volatile. For them to work reliably, spin coherence must be maintained across the device by suppressing spin relaxation. Suppression can be accomplished by structural engineering, such as by confining spin carriers to the lowest subband in a semiconductor quantum wire. Accordingly, we have fabricated 50-nm diameter InSb nanowire spin valves capped with Co and Ni nanocontacts in which a single conduction subband is occupied by electrons at room temperature. This extreme quantum confinement has led to a 10-fold increase in the spin relaxation time due to dramatic suppression of the D’yakonov -Perel’ (DP) spin relaxation mechanism. We have observed the spin-valve and Hanle effects at room temperature in these systems. Observing both effects allowed us to estimate the carrier mobility and the spin relaxation length/time and we found that the latter is ~10 times larger than the value reported in bulk InSb despite a four orders of magnitude decrease in the carrier mobility due to surface roughness scattering. We ascribe this dramatic increase in spin relaxation time to the suppression of the DP relaxation mode due to single subband occupancy. Modulation of spin relaxation rate by an external agent can open new possibilities for spintronic devices. Any agent that can excite electrons from the lowest subband to higher subbands will dramatically increase the DP spin relaxation rate. We have shown that the spin relaxation rate in InSb nanowires can be modulated with infrared light. In the dark, almost all the electrons in the nanowires are in the lowest conduction subband, resulting in near-complete absence of DP relaxation and long spin coherence length. This results in a high resistance state in a spin valve whose ferromagnetic contacts have anti-parallel spin polarizations. Under infrared illumination, higher subbands get populated and the DP spin relaxation mechanism is revived, leading to a three-fold decrease in the spin relaxation length. As a result, injected spins flip in the spacer layer of the spin valve and this causes the spin valve resistance to drop. Therefore, this effect can be exploited to implement an infrared detector. We also studied the transport behavior of a single nanowire (~50 nm diameter) captured between two non-magnetic contact pads. The wire was attached between the pads using dielectrophoresis. A giant (∼10,000,000%) negative magnetoresistance at 39 mT field was observed at room temperature in Cu nanowires contacted with Au contact pads. In these nanowires, potential barriers form at the two Cu/Au interfaces because of Cu oxidation that results in an ultrathin copper oxide layer forming between Cu and Au. Current flows when electrons tunnel through, and/or thermionically emit over these barriers. A magnetic field applied transverse to the direction of current flow along the wire deflects electrons toward one edge of the wire because of the Lorentz force, causing electron accumulation at that edge and depletion at the other. This makes the potential barrier at the accumulated edge shorter and at the depleted edge taller. The modulation of the potential barrier height with a magnetic field dramatically alters the tunneling and/or thermionic emission rate causing a giant magnetoresistance. Currently, effort is underway to demonstrate strain sensitive anisotropic magnetoresistance (AMR) in a single Co-Cu-Co nanowire spin valve. AMR is caused by spin-orbit coupling effects which makes the resistance of a ferromagnet depend on the angle between the direction of current flow and the magnetization. The resistance maximizes when the angle is 00 or 1800 and minimizes when the angle is 900. When an external magnetic field is applied in a direction opposite to a ferromagnet’s magnetization, the latter begins to rotate in the direction of the field and hence its resistance continuously changes. This results in a trough in the magnetoresistance of a spin valve structure between the two fields when the magnetization starts to rotate and when the magnetization completes the rotation. We have observed a magnetoresistance peak (instead of trough) in the Co-Cu-Co spin valve, which is due to the normal spin valve effect that overshadows AMR. However, when an intense infrared light source is brought close to the sample, the peak gets overshadowed by a trough, showing that the AMR effect becomes dominant. We attribute this intriguing feature to the fact that the AMR effect is strongly influenced by strain. Heating by the light source generates strain in the Co contacts owing to unequal thermal expansion of Co and the underlying substrate. We also observed that the AMR effect becomes more pronounced as the light source is brought closer to the sample, resulting in increased heating and hence increased strain generation.

Nanomaterials are widely used in many different products, such as electronics, cosmetics, industrial goods, biomedical uses, and other material applications. The heavy emission of nanomaterials into the environment has motived increasing concern regarding the effects on ecosystems, food chains, and, human health. Plants can tolerate a certain amount of natural nanomaterials, but large amounts of ENMs released from a variety of industries could be toxic to plants and possibly threaten the ecosystem. Employing phytoremediation as a contamination treatment method may show promise. However a pre-requisite to successful treatment is a better understanding of the behavior and effects of nanomaterials within plant systems. This study is designed to investigate the uptake, translocation, bioavailability, and toxicity of gold nanorods in maize plants. Maize is an important food and feed crop that can be used to understand the potential hazardous effects of nanoparticle uptake and distribution in the food chain. The findings could be an important contribution to the fields of phytoremediation, agri-nanotechnology, and nanoparticle toxicity on plants. In the first experiment, hydroponically grown maize seedlings were exposed to similar doses of commercial non-coated gold nanorods in three sizes, 10x34 nm, 20x75 nm, and 40x96 nm. The three nanorod species were suspended in solutions at concentrations of 350 mg/l, 5.8 mg/l, and 14 mg/l, respectively. Maize plants were exposed to all three solutions resulting in considerably lower transpiration and wet biomass than control plants. Likewise, dry biomass was reduced, but the effect is less pronounced than that of transpiration and wet biomass. The reduced transpiration and water content, which eventually proved fatal to exposed plants, were most likely a result of toxic effect of gold nanorod, which appeared to physically hinder the root system. TEM images proved that maize plants can uptake gold particles and accumulate them in root and leaf cells. However, the translocation factor of gold nanorods from root to leaf was very low in this experiment. In the second experiment, maize seedlings were exposed to different (lower) concentrations of gold nanorods measured at 4.5x10-3 mg/l, 0.45 mg/l, and 2.25 mg/l for 10 days. Transpiration and biomass measurements demonstrated that the higher concentration of gold nanorods caused lower water uptake and growth, but lower concentrations did not show a significant toxic effect. According to ICP-MS results, root systems of the exposed plants were surrounded by high concentrations of sorbed nanorods, which physically interfered with uptake pathways and, thus, inhibited plant growth and nutritional uptake.