In this study, we synthesized amphiphilic block copolymer Poly(ethylene glycol)-b-Poly(£`-caprolactone) (PEO-b-PCL), and the mesoporous silica and phenolic were synthesized by using EISA (evaporation induced self-assembly) strategy. The mesoporous carbon also obtained after carbonization. After incorporating the precursors into the mesoporous channels through incipient wetness impregnation and further hydrogen reduction, 3D body-centered cubic (BCC) metal network/silica, metal nanowires/silica, metal/phenolic, and metal/carbon nanocomposites could be obtained. Moreover, metal replica was obtained through HF etching. Transmission electron microscope (TEM) and the small angle X-ray scattering (SAXS) patterns indicate that the parent ordered mesoporous structure was well-maintained during the synthesis process. The X-ray diffraction (XRD) and selected-area electron diffraction (SAED) demonstrate that Pd and Ag were reduced within the channels of mesoporous materials. The pore size distribution and BET surface area of mesoporous materials and metal/mesoporous materials composite were recorded by N2 isotherm adsorption-desorption experiment. In the future, we expect that the mesoporous metal and mesoporous nanocomposite with specific morphologies behave excellent performance in various applications, such as catalysis, gas sensors, nano electronic/optical devices and medical diagnosis.

Bottom-up self-assembly has the potential to fabricate nanostructures with advanced electrical features. DNA templates have been used to enable such self-assembling methods due to their versatility and compatibility with various nanomaterials. This dissertation describes research to advance several different steps of biotemplated nanofabrication, from DNA assembly to characterization. I assembled different nanomaterials including surfactant-coated Au nanorods, DNA-linked Au nanorods and Pd nanoparticles on DNA nanotubes ~10 micrometer long, and on ~400 nm long bar-shaped DNA origami templates. I optimized seeding by changing the surfactant and magnesium ion concentrations in the seeding solution. After successful seeding, I performed electroless plating on those nanostructures to fabricate continuous nanowires. Using the four-point probe technique, I performed resistivity measurements for Au nanowires on DNA nanotubes and obtained values between 9.3 x 10-6 and 1.2 x 10-3 ohm meter. Finally, I demonstrated the directed placement of DNA origami using block copolymer self-assembly. I created a gold nanodot array using block copolymer patterning and metal evaporation followed by lift-off. Then, I used different ligand groups and DNA hybridization to attach DNA origami to the nanodots. The DNA hybridization approach showed greater DNA attachment to Au nanodots than localization by electrostatic interaction. These results represent vital progress in understanding DNA-templated components, nanomaterials, and block copolymer nanolithography. The work in this dissertation shows potential for creating DNA-templated nanodevices and their placement in an ordered array in future nanoelectronics. Each of the described materials and techniques further has potential for addressing the need for increased complexity and integration for future applications.

The constant trend of device miniaturization along with ever-growing list of unusual behaviour of nanoscale materials has fuelled the recent research in fabrication and applications of ultrathin (~2 nm diameter) nanowires. Although semiconductor nanowires of this dimension is well-researched, molecular-scale single-crystalline metal nanowires have not been addressed in details. Such single crystalline Au nanowires are formed by oriented attachment of Au nanoparticles along [111] direction. A very low concentration of extended defects in these wires result in a high electrical conductivity, making them ideal for nanoscale interconnects. Other metal nanowires, e.g. Ag and Cu, have very low absorption co-efficient useful for fabrication of transparent conducting films. On the other hand, because of the reduced dimensions, there exists a tantalizing possibility of dominating quantum effects leading to their application in sensing and actuation. Also, speaking in terms of atomic structure, these systems suffer from intense surface stress, and the atomistic picture can be drastically different from bulk. Thus, although a myriad of applications are possible with ultrathin metal nanowires, a rigorous systematic knowledge of their atomic and electronic structure is not yet available. This thesis is the first one to model such computationally demanding systems with emphasis on their possible applications. In this thesis, we have explored various structural and electronic aspects of one-dimensional ultrathin nanowires with ab initio density functional theory coupled with experiments. The merit of Au nanowires has been tested as nanoscale interconnects. From atomistic point of view, these FCC Au nanowires exhibit an intriguing relaxation mechanism, which has been explored by both theory and experiment. The primary factor governing the relaxation mechanism was found to be the anisotropic surface stress of the bounding facets, and it is extended to explain the relaxation of other metallic nanowires. Our studies suggest that AuNWs of this dimension show semiconductor-like sensitivity towards small chemical analytes and can be used as nanoscale sensors. Also, we have found that further reducing the diameter of the Au-nanowires leads to opening of a band gap.

Reliability, besides the performance, is one of the important key factors of success of any technology. While a product should perform at best as desired, it must also be capable of working for intended period of life without any degradation or wear-out failure, caused by any operational parameter. For example it does no good to manufacture a super fast microprocessor if that fails within few seconds. For the product to meet the intended reliability we must understand the mechanisms that lead to unreliability or failure of the devices. The efforts to understand the fundamental physics of the mechanisms that lead to the failure of the devices has developed a branch of physics named as “reliability physics” of “physics of failure”. On the basis of the understanding of failure mechanism, new design rule can be followed and new material can be applied to improve the reliability of the product. Microelectronic technology also, which is one of the fastest growing technology, has been facing challenges posed by the reliability issues from time to time. There are number of physical failure mechanisms that can affect the reliability of a microelectronic device. Time dependent dielectric breakdown (TDDB), hot carrier damage and current induced damage of interconnects are only to name a few common mechanisms. Among these, the failure of interconnects due to current has been the oldest and persistence reliability issue since the beginning of development of the microelectronic technology. Understanding the physics of the processes that lead to failure of a current carrying film is the main interest of this thesis work. In this investigation, we have carried out a systematic study to understand stability of metal nanowires against damage caused by current stressing and its size dependency. We observe the wires of smaller diameter, having an electronic mean free path larger than or comparable to its diameter are more stable against current stressing. In wires of larger diameter (100 nm or more) the probability of the damage is more. This probably is due to presence of grain boundary type extended defects that allow low energy diffusion path. To our knowledge this is the first experimental investigation to study the stability of nanowires against high current and in-situ measurement of noise during current stressing on them. In the previous investigations by other groups observed that the nanowires without any passivation got damaged by stressing current density which was even lower than the one we used for stressing. To our knowledge this is the first observation of long lasting stability of nanowires, of dimension down to 15 nm, when they are encapsulated in dielectric, an environment that an interconnect has to see in the real integrated circuit devices. In the second chapter we will describe the sample preparation method, characterization of samples and the experimental setups we had used. The results of in-situ noise measurement are described in the third chapter. We will describe our in-situ scanning thermal microscopy study in the fourth chapter. Then in the fifth chapter, we will present our simulation investigations on current induced damage of film. Finally, we will put the concluding remarks on this thesis work and the results in the sixth chapter. We have studied similar damage processes in metal nanowires also. In an appendix we will present our approach and major results of this investigation.

The principal aim of this thesis is to study the electrical transport properties of metal nanowires. Specifically, we have focussed on investigating the resistance fluctuations of Ag and Cu nanowires of diameters ranging from 15nm to 200nm and studied the instabilities that set in when the diameter is reduced below a certain range. The nanowires were grown electrochemically inside polycarbonate and alumina templates. X-ray diffraction studies on the samples showed the presence of a HCP 4H phase in the Ag nanowires in addition to the usual FCC phase, which is seen in bulk Ag. The relative ratios of these two phases were a maximum for nanowires of diameter 30nm. The X-ray diffraction studies also showed that the samples were of high chemical purity. TEM studies revealed that the wires are single crystalline in nature. Once the wires are released from the template, the wires of diameter 15nm were seen to break down spontaneously into globules due to Rayleigh instability. Wires of larger diameter tended to neck down to smaller radius but did not break down completely into globules. Both the Ag and Cu nanowire arrays had a fairly linear temperature dependence of resistance down to about 100K and reached a residual resistance below 40-50K. The temperature dependence of resistance could be fitted to a Bloch-Grüneisen formula over the entire temperature range. We found that n = 5 gave the best fit for the wires of all diameters showing that the dominant contribution to the temperature dependence of the resistivity in theses nanowires come from electron-acoustic phonon interactions. The resistivities of the wires were seen to increase as the wire diameter was decreased. This increase in the resistivity of the wires could be attributed to surface scattering of conduction electrons. In nanowires of diameter 15nm of both Ag and Cu, the relative variance of resistance fluctuations <(ΔR)2>/R2 showed a prominent peak at around ~ 220K for the Ag nanowire and ~ 260K for the Cu wire. Ag wires of diameter 20nm showed a much-reduced peak in noise at a somewhat higher temperature while this feature was completely absent in wires of larger diameter as also for the reference Ag film. The noise in wires of diameter larger than 20nm was similar to that of the reference film. For wires of diameter 15nm as we approach T*, the power spectral density showed a severe deviation from 1/f nature. We could establish that the extra fluctuation seen in the nanowires of the narrowest diameters could originate from the Rayleigh instability. The measured resistance fluctuation was found to have a magnitude similar to that estimated from a simple model of a wire showing volume preserving fluctuation. In the temperature range T ≤ 100K we observed very large non-Gaussian resistance fluctuations in a narrow temperature range for Ag and Cu wires of diameter 30nm with the fluctuations becoming much smaller as the diameter of the wires deviated from 30nm. In wires of diameter larger than 50nm the noise was almost independent of temperature in this range. The power spectrum of the resistance fluctuations also developed a large additional low frequency component near TP. We could establish that the appearance of this noise at a certain temperature (~30 – 50K) is due to the onset of martensite strain accommodation in these nanowires. To summarize, we measured the resistance and resistance fluctuations of Ag and Cu nanowires of diameters ranging from 15nm to 200nm in the temperature range 4.2-300K. The temperature dependence of resistance could be fitted to a Bloch-Grüneisen formula over the entire temperature range of measurement (4.2K-300K). The contribution of electron-phonon scattering to the resistivity was found to be similar to that of bulk. The defect free nature of our samples allowed us to identify two novel sources of noise in these nanowires. At high temperatures Rayleigh instability causes the noise levels in wires of diameter around 15nm to increase. At lower temperatures the formation of martensite state leads to an increase in noise in wires of small diameters.

Nanotechnology builds devices from the bottom up with atomic accuracy. Among the basic nano-components to fabricate such devices, semiconductor nanoparticle quantum dots (QDs), metal nanocrystals, proteins, and nucleic acids have attracted most interests due to their potential in optical, biomedical, and electronic areas. The major objective of this research was to prepare nano-components in order to fabricate functional nano-scale devices. This research consisted of three projects. In the first two projects, we incorporated two desirable characteristics of QDs, which are their abilities to serve as donors in fluorescence energy transfer (FRET) and surface energy transfer (SET) as well as to do multiplexing, to engineer QD-based nanoconjugates for optical and biomedical applications. Immobilizing luminescent semiconductor CdSe/ZnS QDs to a solid platform for QD-based biosensors offers advantages over traditional solution-based assays. In the first project, we designed highly sensitive CdSe/ZnS QD SET-based probes using gold nanoparticles (AuNPs) as FRET acceptors on polystyrene (PS) microsphere surfaces. The emission of PS-QD was significantly quenched and restored when the AuNPs were attached to and then removed from the surface. The probes were sensitive enough to analyze signals from a single bead and for use in optical applications. The new PS-QD-AuNP SET platform opens possibilities to carry out both SET and FRET assays in microparticle-based platforms and in microarrays. In the second project, we applied the QD-encoded microspheres in FRET-based analysis for bio-applications. QDs and Alexa Fluor 660 (A660) fluorophores are used as donors and acceptors respectively via a hairpin single stranded DNA. FRET between QD and A660 on the surface of polystyrene microspheres resulted in quenching of QD luminescence and increased A660 emission. QD emission on polystyrene x microspheres was restored when the targeted complementary DNA hybridized the hairpin strand and displaced A660 away from QDs. The third project involved fabrication of different nanoconjugates via self-assembly of template-based metal nanowires and metal nanoparticles using oligonucleotides as linkers. These nanoconjugates can serve as building blocks in nano-electronic circuits. The template method restricted the oligonucleotides attachment to the tip of the nanowires. Nanowires tagged with hybridizable DNA could connect to complementary DNA-modified metal crystals in a position-specific manner.

Actuellement, le développement à grande échelle des piles à combustible à membrane échangeuse de protons est limité par l’utilisation importante de platine ainsi que par une faible durabilité des dispositifs. Les électrodes conventionnelles, dénommées Pt/C, sont constituées de nanoparticules de platine déposées sur un support composé de nanoparticules de carbone. Le but de cette thèse est de proposer, élaborer et tester en pile à combustible complète des nanostructures composées de nanotubes de platine autosupportés afin d’augmenter la durée de vie des dispositifs et de réduire la quantité de platine utilisée. Afin de réaliser de telles nanostructures, un moule d’alumine nanoporeuse constitué de nanopores verticaux est élaboré par oxydation électrochimique d’aluminium. Cette matrice de nanopores permet de réaliser une croissance confinée de nanotubes de platine par évaporation de métal sous vide ou par des dépôts électrochimiques. Une membrane de Nafion® est par la suite pressée à chaud et l’alumine est dissoute. Des nanotubes de platine autosupportés sont ainsi obtenus à la surface de la membrane. Afin de comprendre le fonctionnement de ces électrodes en pile à combustible complète, une méthode de quantification des pertes limitant les performances d’électrodes standards de Pt/C a été utilisée. La nanostructuration des électrodes permet d’augmenter significativement la durée de vie des dispositifs et de diminuer les pertes de transport d’oxygène. La principale limitation mise en évidence est des pertes cinétiques importantes en raison de la faible surface spécifique de platine développée. / The two main drawbacks of Proton Exchange Membrane Fuel Cells (PEMFC) are the low electrode durability and the high platinum loading (electrocatalyst for oxygen reduction reaction). Currently, PEMFC electrodes, named as Pt/C, are made of platinum nanoparticles supported by carbon nanoparticles. The aim of this PhD work is to propose, elaborate and test in complete fuel cell new electrode nanostructure consists in self-supported platinum nanotubes. We target a reduction in the platinum loading and an increase in the electrode durability. In order to control nanostructure geometries, a porous alumina mold is used. This template is obtained by electrochemical anodization and vertically aligned nanopores are obtained. Platinum is subsequently deposited onto pore walls by e-beam evaporation or electrochemical deposition processes. After the hot pressing of the Nafion® proton exchange membrane, the porous alumina mold is etched and platinum nanotubes are stuck and self-supported onto the membrane. A part of this work is dedicated to the quantification of performances losses of Pt/C electrodes and nanostructured electrodes in complete fuel cell test operating conditions. Nanostructured electrodes exhibit high durability and easy oxygen access on catalyst surface compared to Pt/C electrodes. However, some losses kinetics remains due to the low catalyst specific area.