Dissertations / Theses on the topic 'Nanoscale Dimensions'

The extraordinary magnetoresistance (EMR) in metal-semiconductor hybrid structures was first demonstrated using a van der Pauw configuration for a circular semiconductor wafer with a concentric metallic inclusion in it. This effect depends on the orbital motion of carriers in an external magnetic field, and the remarkably high magnetoresistance response observed suggests that the geometry of the metallic inclusion can be optimized to significantly enhance the EMR. Here we consider the theory and simulations to achieve this goal by comparing both two-dimensional as well as three-dimensional structures in an external magnetic field to evaluate the EMR in them. Examples of structures that are compatible with present day technological capabilities are given together with their expected responses in terms of EMR. For a 10 micron 2D square structure with a square metallic inclusion, we see a MR up to 10^7 percent for an applied magnetic field of 1 Tesla.

In this study, the thermal properties of low dimensional materials such as graphene and boron nitride nanotube were investigated. As one of important heat transfer characteristics, interfacial thermal resistance (ITR) between graphene and Cu film was estimated by both experiment and simulation. In order to characterize ITR, the micropipette sensing technique was utilized to measure the temperature profile of suspended and supported graphene on Cu substrate that is subjected to continuous wave laser as a point source heating. By measuring the temperature of suspended graphene, the intrinsic thermal conductivity of suspended graphene was measured and it was used for estimating interfacial thermal resistance between graphene and Cu film. For simulation, a finite element method and a multiparameter fitting technique were employed to find the best fitting parameters. A temperature profile on a supported graphene on Cu was extracted by a finite element method using COMSOL Multiphysics. Then, a multiparameter fitting method using MATLAB software was used to find the best fitting parameters and ITR by comparing experimentally measured temperature profile with simulation one. In order to understand thermal transport between graphene and Cu substrate with different interface distances, the phonon density of states at the interface between graphene and Cu substrate was calculated by MD simulation.As another low dimensional material for thermal management applications, the thermal conductivity of BNNT was measured by nanoscale thermometry. For this work, a noble technique combining a focused ion beam (FIB) and nanomanipulator was employed to pick and to place a single BNNT on the desired location. The FIB technology was used to make nanoheater patterns (so called nanothermometer) on a prefabricated microelectrode device by conventional photolithography processes. With this noble technique and the nanoheater thermometry, the thermal conductivity of BNNT was successfully characterized by temperature gradient and heat flow measurements through BNNT.

This project is a systematic study regarding the discovery and design of nanomaterials with potential applications in electronic devices. It reveals several promising candidates such as a new phase of transition metal dichalcogenides and the two-dimensional ionic boron sheet with novel electronic properties, which enrich the family of two-dimensional materials. The comprehensive calculations would also be a good guidance for the experimental realisation in the near future.

In this study, the thermal properties of low dimensional materials such as graphene and boron nitride nanotube were investigated. As one of important heat transfer characteristics, interfacial thermal resistance (ITR) between graphene and Cu film was estimated by both experiment and simulation. In order to characterize ITR, the micropipette sensing technique was utilized to measure the temperature profile of suspended and supported graphene on Cu substrate that is subjected to continuous wave laser as a point source heating. By measuring the temperature of suspended graphene, the intrinsic thermal conductivity of suspended graphene was measured and it was used for estimating interfacial thermal resistance between graphene and Cu film. For simulation, a finite element method and a multiparameter fitting technique were employed to find the best fitting parameters. A temperature profile on a supported graphene on Cu was extracted by a finite element method using COMSOL Multiphysics. Then, a multiparameter fitting method using MATLAB software was used to find the best fitting parameters and ITR by comparing experimentally measured temperature profile with simulation one. In order to understand thermal transport between graphene and Cu substrate with different interface distances, the phonon density of states at the interface between graphene and Cu substrate was calculated by MD simulation.As another low dimensional material for thermal management applications, the thermal conductivity of BNNT was measured by nanoscale thermometry. For this work, a noble technique combining a focused ion beam (FIB) and nanomanipulator was employed to pick and to place a single BNNT on the desired location. The FIB technology was used to make nanoheater patterns (so called nanothermometer) on a prefabricated microelectrode device by conventional photolithography processes. With this noble technique and the nanoheater thermometry, the thermal conductivity of BNNT was successfully characterized by temperature gradient and heat flow measurements through BNNT.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.
Page 138 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (pages 121-137).
The advent of a broad class of two-dimensional (2D) electronic materials has provided avenues to create and study designer electronic quantum phases. The coexistence of superconductivity, magnetism, density waves, and other ordered phases on the surfaces and interfaces of these 2D materials are governed by interactions which can be experimentally tuned with increasing precision. This motivates the need to develop spectroscopic probes that are sensitive to these tuning parameters, with the objective of studying the electronic properties and emergence of order in these materials. In the first part of this thesis, we report on spectroscopic studies of the topological semimetal antimony (Sb). Our simultaneous observation of Landau quantization and quasiparticle interference phenomena on this material enables their quantitative reconciliation - after two decades of their study on various materials. We use these observations to establish momentum-resolved scanning tunneling microscopy (MR-STM) as a robust nanoscale band structure probe, and reconstruct the multi-component dispersion of Sb(111) surface states. We quantify surface state parameters relevant to spintronics applications, and clarify the relationship between bulk conductivity and surface state robustness. At low momentum, we find a crossover in the single particle behavior from massless Dirac to massive Rashba character - a unique signature of topological surface states. In the second part of this thesis, we report on the spectroscopic study of charge density wave (CDW) order in the dichalcogenide 2H-NbSe2 - a model system for understanding the interplay of coexisting CDW and superconducting phases. We detail the observation of a previously unknown unidirectional (stripe) CDW smoothly interfacing with the familiar triangular CDW on this material. Our low temperature measurements rule out thermal fluctuations and point to local strain as the tuning parameter for this quantum phase transition. The distinct wavelengths and tunneling spectra of the two CDWs, in conjunction with band structure calculations, enable us to resolve two longstanding debates about the anomalous spectroscopic gap and the role of Fermi surface nesting in the CDW phase of NbSe2. Our observations motivate further spectroscopic studies of the phase evolution of the CDW, and of NbSe 2 as a prototypical strong coupling density wave system in the vicinity of a quantum critical point.
by Anjan Soumyanarayanan.
Ph.D.

We report the design and assembly of three-dimensional (3D) multi-cellular liver models comprised of primary rat hepatocytes, liver sinusoidal endothelial cells (LSECs), and Kupffer cells (KCs). LSECs and KCs in the liver model were separated from hepatocytes by a nanoscale, detachable, optically transparent chitosan and hyaluronic acid (HA) polyelectrolyte multilayer (PEM) film. The properties of the PEM were tuned to mimic the Space of Disse found in liver. The thickness of the detachable PEM was 650 to 1000 nm under hydrated conditions. The Young's modulus of the PEM was approximately 42 kPa, well within the range of modulus values reported for bulk liver. The 3D liver models comprised of all three cell types and a detachable PEM exhibited stable urea production and increased albumin secretion over a 12 day culture period. Additionally, the 3D liver model maintained the phenotype of both LSECs and KCs over the 12 day culture period, verified by CD32b and CD163 staining, respectively. Additionally, CYP1A1 enzyme activity increased significantly in the 3D liver models. The number of hepatocytes in the 3D liver model increased by approximately 60% on day 16 of culture compared to day 4 indicating. Furthermore, only the 3D hepatic model maintained cellular compositions virtually identical to those found in vivo. DNA microarray measurements were conducted on the hepatocyte fractions of the 3D liver mimic to obtain insights into hepatic processes. Gene sets up-regulated in the 3D liver model were related to proliferation, migration, and deposition of extracellular matrix, all functions observed in regenerating hepatocytes. Taken together, these results suggest that inter-cellular signaling between the different cell types in the 3D liver model led to increased hepatic functions. To the best of our knowledge, this is the first study where three of the major hepatic cell types have been incorporated into a model that closely mimics the structure of the sinusoid. These studies demonstrate that the multi-cellular liver models are physiologically relevant. Such models are very promising to conduct detailed investigations into hepatic inter-cellular signaling.
Ph. D.

One dimensional carbon nanotubes (CNTs) and two-dimensional layered materials like graphene, MoS2, hexagonal boron nitride (hBN), etc. with different electrical and mechanical properties are great candidates for many applications in the future. In this study the synthesis and growth of carbon nanotubes on both conducting graphene and graphite substrates as well as insulating hBN substrate with precise crystallographic orientation is achieved. We show that the nanotubes have a clear preference to align to specific crystal directions of the underlying graphene or hBN substrate. On thicker flakes of graphite, the edges of these 2D materials can control the orientation of these carbon nanotubes. This integrated aligned growth of materials with similar lattices provides a promising route to achieving intricate nanoscale electrical circuits. Furthermore, short channel nanoscale devices consisting of the heterostructure of 1D and 2D materials are fabricated. In these nanoscale devices the nanogap is created due to etching of few layer graphene flake through hydrogenation and the channel is either carbon nanotubes or 2D materials like graphene and MoS2. Finally the transport properties of these nanoscale devices is studied.

The properties of a broad range of materials are due to processes which occur at the nanoscale. Recently, an increasing interest has been devoted to nanostructured materials, in which the basic components are nanoscopic, and low-dimensional nanomaterials such as nanoparticles, nanowires and layered materials, in which one or more dimensions are confined. This thesis deals with nanostructured materials, in particular based on graphene, such as Graphene Nanofoams and Pillared Graphene Frameworks, and low dimensional nanomaterials such as SiC/SiO2 core/shell nanowires and graphene layers. The work is divided in four parts treating four different topics with the underlying theme of material modeling, the first two parts deal with mechanical properties and gas treatment applications, for which a description at the atomistic level is adequate, while the third and the forth focus on X-ray spectra and electron holography simulations for which electronic structure calculations are needed. The present thesis gives a general overview on various computational approaches that are useful in modeling novel low dimensional and nanostructured materials, using these approaches in dealing with specific systems.

The properties of a broad range of materials are due to processes which occur at the nanoscale. Recently, an increasing interest has been devoted to nanostructured materials, in which the basic components are nanoscopic, and low-dimensional nanomaterials such as nanoparticles, nanowires and layered materials, in which one or more dimensions are confined. This thesis deals with nanostructured materials, in particular based on graphene, such as Graphene Nanofoams and Pillared Graphene Frameworks, and low dimensional nanomaterials such as SiC/SiO2 core/shell nanowires and graphene layers. The work is divided in four parts treating four different topics with the underlying theme of material modeling, the first two parts deal with mechanical properties and gas treatment applications, for which a description at the atomistic level is adequate, while the third and the forth focus on X-ray spectra and electron holography simulations for which electronic structure calculations are needed. The present thesis gives a general overview on various computational approaches that are useful in modeling novel low dimensional and nanostructured materials, using these approaches in dealing with specific systems.

Hybrid bio-robotics is a discipline that aims at integrating biological entities with synthetic materials to incorporate features from biological systems that have been optimized through millions of years of evolution and are difficult to replicate in current robotic systems. We can find examples of this integration at the nanoscale, in the field of catalytic nano- and micromotors, which are particles able to self-propel due to catalytic reactions happening in their surface. By using enzymes, these nanomotors can achieve motion in a biocompatible manner, finding their main applications in active drug delivery. At the microscale, we can find single-cell bio-swimmers that use the motion capabilities of organisms like bacteria or spermatozoa to transport microparticles or microtubes for targeted therapeutics or bio-film removal. At the macroscale, cardiac or skeletal muscle tissue are used to power small robotic devices that can perform simple actions like crawling, swimming, or gripping, due to the contractions of the muscle cells. This dissertation covers several aspects of these kinds of devices from the nanoscale to the macro-scale, focusing on enzymatically propelled nano- and micromotors and skeletal muscle tissue bio-actuators and bio-robots. On the field of enzymatic nanomotors, there is a need for a better description of their dynamics that, consequently, might help understand their motion mechanisms. Here, we focus on several examples of nano- and micromotors that show complex dynamics and we propose different strategies to analyze their motion. We develop a theoretical framework for the particular case of enzymatic motors with exponentially decreasing speed, which break the assumptions of constant speed of current methods of analysis and need different strategies to characterize their motion. Finally, we consider the case of enzymatic nanomotors moving in complex biological matrices, such as hyaluronic acid, and we study their interactions and the effects of the catalytic reaction using dynamic light scattering, showing that nanomotors with negative surface charge and urease-powered motion present enhanced parameters of diffusion in hyaluronic acid. Moving towards muscle-based robotics, we investigate the application of 3D bioprinting for the bioengineering of skeletal muscle tissue. We demonstrate that this technique can yield well-aligned and functional muscle fibers that can be stimulated with electric pulses. Moreover, we develop and apply a novel co-axial approach to obtain thin and individual muscle fibers that resemble the bundle-like organization of native skeletal muscle tissue. We further exploit the versatility of this technique to print several types of materials in the same process and we fabricate bio-actuators based on skeletal muscle tissue with two soft posts. Due to the deflection of these cantilevers when the tissue contracts upon stimulation, we can measure the generated forces, therefore obtaining a force measurement platform that could be useful for muscle development studies or drug testing. With these applications in mind, we study the adaptability of muscle tissue after applying various exercise protocols based on different stimulation frequencies and different post stiffness, finding an increase of the force generation, especially at medium frequencies, that resembles the response of native tissue. Moreover, we adapt the force measurement platform to be used with human-derived myoblasts and we bioengineer two models of young and aged muscle tissue that could be used for drug testing purposes. As a proof of concept, we analyze the effects of a cosmetic peptide ingredient under development, focusing on the kinematics of high stimulation contractions. Finally, we present the fabrication of a muscle-based bio-robot able to swim by inertial strokes in a liquid interface and a nanocomposite-laden bio-robot that can crawl on a surface. The first bio-robot is thoroughly characterized through mechanical simulations, allowing us to optimize the skeleton, based on a serpentine or spring-like structure. Moreover, we compare the motion of symmetric and asymmetric designs, demonstrating that, although symmetric bio-robots can achieve some motion due to spontaneous symmetry breaking during its self-assembly, asymmetric bio-robots are faster and more consistent in their directionality. The nanocomposite-laden crawling bio-robot consisted of embedded piezoelectric boron nitride nanotubes that improved the differentiation of the muscle tissue due to a feedback loop of piezoelectric effect activated by the same spontaneous contractions of the tissue. We find that bio-robots with those nanocomposites achieve faster motion and stronger force outputs, demonstrating the beneficial effects in their differentiation. This research presented in this thesis contributes to the development of the field of bio-hybrid robotic devices. On enzymatically propelled nano- and micromotors, the novel theoretical framework and the results regarding the interaction of nanomotors with complex media might offer useful fundamental knowledge for future biomedical applications of these systems. The bioengineering approaches developed to fabricate murine- or human-based bio-actuators might find applications in drug screening or to model heterogeneous muscle diseases in biomedicine using the patient’s own cells. Finally, the fabrication of bio-hybrid swimmers and nanocomposite crawlers will help understand and improve the swimming motion of these devices, as well as pave the way towards the use of nanocomposite to enhance the performance of future actuators.
La bio-robótica híbrida es una disciplina cuyo objetivo es la integración de entidades biológicas con materiales sintéticos para superar los desafíos existentes en el campo de la robótica blanda, incorporando características de los sistemas biológicos que han sido optimizadas durante millones de años de evolución natural y no son fáciles de reproducir artificialmente. Esta tesis cubre varios aspectos de este tipo de dispositivos desde la nanoescala a la macroescala, enfocándose en nano- y micromotores propulsados enzimáticamente y bio-actuadores y bio-robots basados en tejido muscular esquelético. En el campo de nanomotores enzimáticos, existe la necesidad de encontrar mejores modelos que puedan describir la dinámica de su movimiento para llegar a entender sus mecanismos de propulsión subyacentes. Aquí, nos enfocamos en diversos ejemplos de nano- y micromotores que muestran dinámicas de movimiento complejas y proponemos diferentes estrategias que se pueden utilizar para analizar y caracterizar este movimiento. Moviéndonos hacia robots basados en células musculares, investigamos la aplicación de la técnica de bioimpresión en 3D para la biofabricación de músculo esquelético. Demostramos que esta técnica puede producir fibras musculares funcionales y bien alineadas que puede ser estimuladas y contraerse con pulsos eléctricos. Investigamos la versatilidad de esta técnica para imprimir varios tipos de materiales en el mismo proceso y fabricamos bio-actuadores basados en músculo esquelético. Debido a los movimientos de unos postes gracias a las contracciones musculares, podemos obtener medidas de la fuerza ejercida, obteniendo una plataforma de medición de fuerzas que podría ser de utilidad para estudios sobre el desarrollo del músculo o para testeo de fármacos. Finalmente, presentamos la fabricación de un bio-robot basado en músculo esquelético capaz de nadar en la superficie de un líquido y un bio-robot con nanocompuestos incrustados que puede arrastrarse por una superficie sólida. El primer de ellos es minuciosamente caracterizado a través de simulaciones mecánicas, permitiéndonos optimizar su esqueleto, basado en una estructura tipo serpentina o muelle. El segundo bio-robot contiene nanotubos piezoeléctricos incrustados en su tejido, los cuales ayudan en la diferenciación del músculo debido a una retroalimentación basada en su efecto piezoeléctrico y activada por las contracciones espontáneas del tejido. Mostramos que estos bio-robots pueden generar un movimiento más rápido y una mayor generación de fuerza, demostrando los efectos beneficiales en la diferenciación del tejido.

The use of full wave electromagnetic modeling and simulation tools allows for accurate performance predictions of unique RF structures that exhibit multi-dimensional scales. Full wave simulation tools need to cover the broad range of frequency including RF and terahertz bands that is focused as RF technology is developed. In this dissertation, three structures with multi-dimensional scales and different operating frequency ranges are modeled and simulated. The first structure involves nanostructured solar cells. The silicon solar cell design is interesting research to cover terahertz frequency range in terms of the economic and environmental aspects. Two unique solar cell surfaces, nanowire and branched nanowire are modeled and simulated. The surface of nanowire is modeled with two full wave simulators and the results are well-matched to the reference results. This dissertation compares and contrasts the simulators and their suitability for extensive simulation studies. Nanostructured Si cells have large and small dimensional scales and the material characteristics of Si change rapidly over the solar spectrum. The second structure is a reconfigurable four element antenna array antenna operating at 60 GHz for wireless communications between computing cores in high performance computing systems. The array is reconfigurable, provides improved transmission gain between cores, and can be used to create a more failure resilient computing system. The on-chip antenna array involves modeling the design of a specially designed ground plane that acts as an artificial magnetic conductor. The work involves modeling antennas in a complex computing environment. The third structure is a unique collar integrated zig-zag antenna that operates at 154.5 MHz for use as a ground link in a GPS based location system for wildlife tracking. In this problem, an intricate antenna is modeled in the proximity of an animal. Besides placing a low frequency antenna in a constricted area (the collar), the antenna performance near the large animal body must also be considered. Each of these applications requires special modeling details to take into account the various dimensional scales of the structures and interaction with complex media. An analysis of the challenges and limits of each specific problem will be presented.

Nanostructures were formed on diced specimens of several silicon carbide polytypes and silicon using electron beam lithography. A general introduction to nanostructure synthesis and electron beam lithography,are presented. A scanning electron microscope was retrofitted with a commercially available electron beam lithography package and an electrostatic beam blanker to permit nanoscale lithography to be performed. A process was first developed and optimized on silicon substrates to expose, poly-methyl-methacrylate (PMMA) resist with an electron beam to make nanoscale nickel masks for reactive ion etching. The masks consist of an array of nickel dots that range in size from 20 to 100 nm in diameter. Several nanoscale structures were then fabricated in silicon carbide using electron beam lithography. The structures produced are characterized by field emission Scanning Electron Microscopy.

Single-molecule DNA experiments dealing with statics and dynamics in nanoconfined systems are typically performed via fluorescence microscopy, yielding access to information regarding molecule conformation but no direct information regarding nanoscale forces. In this experiment, two single-molecule manipulation tools were combined, optical trapping and nanoconfinement, to develop a novel assay that can yield information regarding both molecule conformation and forces experienced in confinement. Single 200nm polystyrene beads are trapped inside 340x340nm silica nanochannels with an entropic nano-slit barrier. These beads are then used as "nano-pistons" or "nanodozers," to apply compressive forces to single-molecules confined inside the nanochannels. In particular, a single nanodozer is used to push a DNA molecule against the barrier, enabling measurements of force versus molecule compression. By carefully calibrating the trap via assessing Brownian motion of an oscillating bead confined in a nanochannel, force-compression curves were obtained and were compared to polymer physics models for a cavity confined chain.
Les experiences traitant de la statique et de la dynamique d'une seule molecule d'ADN dans des systemes nanoconfines sont generalement effectuees par microscopie de fluorescence, donnant acces a l'information concernant la conformation moleculaire, mais aucune information directe concernant les forces a l'echelle nanometrique. Dans cette experience, nous combinons deux outils de manipulation d'une seule molecule, le piegeage optique et le nanoconfinement, an de developper un nouveau test pouvant donner des informations a la fois sur la conformation de la molecule et sur les forces subies en confinement. Des billes de polystyrene de 200nm sont piegees a l'interieur de nanocanaux de silice de dimensions 340x340nm avec une barriere entropique a nano-fente. Ces billes sont ensuite utilisees en tant que "nano-pistons" ou "nanodozers" pour appliquer des forces de compression aux molecules individuelles confinees a l'interieur des nanocanaux. En particulier, un nanodozer unique est utilise pour pousser une molecule d'ADN contre la barriere, permettant une mesure de la force en fonction de la compression moleculaire. En prenant soin de calibrer notre trappe l'aide du mouvement Brownien d'une bille oscillant dans un nanocanal, nous obtenons une courbe force-compression que nous comparons a des modeles physiques de polymeres pour une chaine confinee dans une cavite.

Pillared-graphene structure (PGS) is a novel three-dimensional structure consists of parallel graphene sheets that are separated by carbon nanotube (CNT) pillars that is proposed for efficient thermal management of electronics. For microscale simulations, finite element analyses were carried out by imposing a heat flux on several PGS configurations using a Gaussian pulse. The temperature gradient and distribution in the structures was evaluated to determine the optimum design for heat transfer. The microscale simulations also included conducting a mesh-independent study to determine the optimal mesh element size and shape. For nanoscale simulations, Scienomics MAPS software (Materials And Processes Simulator) along with LAMMPS (Large-scale Atomic/ Molecular Massively Parallel Simulator) were used to calculate the thermal conductivity of different configurations and sizes of PGS. The first part of this research included investigating PGS when purely made of carbon atoms using non-equilibrium molecular dynamics (NEMD). The second part included investigating the structure when supported by a copper foil (or substrate); mimicking production of PGS on copper. The micro- and nano-scale simulations show that PGS has a great potential to manage heat in micro and nanoelectronics. The fact that PGS is highly tunable makes it a great candidate for thermal management applications. The simulations were successfully conducted and the thermal behavior of PGS at the nanoscale was characterized while accounting for phonon scattering the graphene/CNT junction as well as when PGS is supported by a copper substrate.

At the beginning of this thesis, basic and advanced device fabrication process which I haveexperienced during study such as top-down and bottom-up approach for the nanoscale devicefabrication technique have been described. Especially, lithography technology has beenfocused because it is base of the modern device fabrication. For the advanced device structure,etching technique has been investigated in detail.The characterization of FET has been introduced. For the practical consideration in theadvanced FET, several parameter extraction techniques have been introduced such as Yfunction,split C-V etc.FinFET is one of promising alternatives against conventional planar devices. Problem ofFinFET is surface roughness. During the fabrication, the etching process induces surfaceroughness on the sidewall surfaces. Surface roughness of channel decreases the effectivemobility by surface roughness scattering. With the low temperature measurement andmobility analysis, drain current through sidewall and top surface was separated. From theseparated currents, effective mobilities were extracted in each temperature conditions. Astemperature lowering, mobility behaviors from the transport on each surface have differenttemperature dependence. Especially, in n-type FinFET, the sidewall mobility has strongerdegradation in high gate electric field compare to top surface. Quantification of surfaceroughness was also compared between sidewall and top surface. Low temperaturemeasurement is nondestructive characterization method. Therefore this study can be a propersurface roughness measurement technique for the performance optimization of FinFET.As another quasi-1 D nanowire structure device, 3D stacked SiGe nanowire has beenintroduced. Important of strain engineering has been known for the effective mobility booster.The limitation of dopant diffusion by strain has been shown. Without strain, SiGe nanowireFET showed huge short channel effect. Subthreshold current was bigger than strained SiGechannel. Temperature dependent mobility behavior in short channel unstrained device wascompletely different from the other cases. Impurity scattering was dominant in short channelunstrained SiGe nanowire FET. Thus, it could be concluded that the strain engineering is notnecessary only for the mobility booster but also short channel effect immunity.Junctionless FET is very recently developed device compare to the others. Like as JFET,junctionless FET has volume conduction. Thus, it is less affected by interface states.Junctionless FET also has good short channel effect immunity because off-state ofjunctionless FET is dominated pinch-off of channel depletion. For this, junctionless FETshould have thin body thickness. Therefore, multi gate nanowire structure is proper to makejunctionless FET.Because of the surface area to volume ratio, quasi-1D nanowire structure is good for thesensor application. Nanowire structure has been investigated as a sensor. Using numericalsimulation, generation-recombination noise property was considered in nanowire sensor.Even though the surface area to volume ration is enhanced in the nanowire channel, devicehas sensing limitation by noise. The generation-recombination noise depended on the channelgeometry. As a design tool of nanowire sensor, noise simulation should be carried out toescape from the noise limitation in advance.The basic principles of device simulation have been discussed. Finite difference method andMonte Carlo simulation technique have been introduced for the comprehension of devicesimulation. Practical device simulation data have been shown for examples such as FinFET,strongly disordered 1D channel, OLED and E-paper
At the beginning of this thesis, basic and advanced device fabrication process which I haveexperienced during study such as top-down and bottom-up approach for the nanoscale devicefabrication technique have been described. Especially, lithography technology has beenfocused because it is base of the modern device fabrication. For the advanced device structure,etching technique has been investigated in detail.The characterization of FET has been introduced. For the practical consideration in theadvanced FET, several parameter extraction techniques have been introduced such as Yfunction,split C-V etc.FinFET is one of promising alternatives against conventional planar devices. Problem ofFinFET is surface roughness. During the fabrication, the etching process induces surfaceroughness on the sidewall surfaces. Surface roughness of channel decreases the effectivemobility by surface roughness scattering. With the low temperature measurement andmobility analysis, drain current through sidewall and top surface was separated. From theseparated currents, effective mobilities were extracted in each temperature conditions. Astemperature lowering, mobility behaviors from the transport on each surface have differenttemperature dependence. Especially, in n-type FinFET, the sidewall mobility has strongerdegradation in high gate electric field compare to top surface. Quantification of surfaceroughness was also compared between sidewall and top surface. Low temperaturemeasurement is nondestructive characterization method. Therefore this study can be a propersurface roughness measurement technique for the performance optimization of FinFET.As another quasi-1 D nanowire structure device, 3D stacked SiGe nanowire has beenintroduced. Important of strain engineering has been known for the effective mobility booster.The limitation of dopant diffusion by strain has been shown. Without strain, SiGe nanowireFET showed huge short channel effect. Subthreshold current was bigger than strained SiGechannel. Temperature dependent mobility behavior in short channel unstrained device wascompletely different from the other cases. Impurity scattering was dominant in short channelunstrained SiGe nanowire FET. Thus, it could be concluded that the strain engineering is notnecessary only for the mobility booster but also short channel effect immunity.Junctionless FET is very recently developed device compare to the others. Like as JFET,junctionless FET has volume conduction. Thus, it is less affected by interface states.Junctionless FET also has good short channel effect immunity because off-state ofjunctionless FET is dominated pinch-off of channel depletion. For this, junctionless FETshould have thin body thickness. Therefore, multi gate nanowire structure is proper to makejunctionless FET.Because of the surface area to volume ratio, quasi-1D nanowire structure is good for thesensor application. Nanowire structure has been investigated as a sensor. Using numericalsimulation, generation-recombination noise property was considered in nanowire sensor.Even though the surface area to volume ration is enhanced in the nanowire channel, devicehas sensing limitation by noise. The generation-recombination noise depended on the channelgeometry. As a design tool of nanowire sensor, noise simulation should be carried out toescape from the noise limitation in advance.The basic principles of device simulation have been discussed. Finite difference method andMonte Carlo simulation technique have been introduced for the comprehension of devicesimulation. Practical device simulation data have been shown for examples such as FinFET,strongly disordered 1D channel, OLED and E-paper

碩士
國立清華大學
電子工程研究所
101
Recently, optical tweezers has been created various dimensions of periodic potential lattice for affecting the behavior of particles. According to the limitation of diffraction limit, it is difficult to shrink the experiment into nanoscale. In recent, plasmanic enhanced optical trapping can overcome the limitation of traditional optical tweezers because the surface plasmon concentrate light far below the diffraction limits and enhance optical intensity by resonance. In this thesis, we research the transport and trapping behavior of nanospheres of diameter 500 nm and 100 nm in two-dimensional nanoscale plasmanic optical lattice. Optical potential of the lattice is created by a two-dimensional of gold nanostructure array, and the plasmon resonance is illuminated by Gaussian beam. We observe the transport and trapping behavior of nanospheres in this optical potential. The stacking of diameter 500 nm spheres into hexagonal closed pack crystalline in this potential is also observed clearly. In this thesis, we introduce the setup of optical system clearly and make an explanation about the calculation and fabrication process of plasmonic structures.

碩士
國立成功大學
機械工程學系碩博士班
97
In this study, we apply the modified discrete ordinates method (MDOM) and the discrete ordinates method (DOM) to two-dimensional phonon radiative transport. Two cases, one with a hot boundary and the other with an internal heat source, are considered. The results of the two cases, respectively, obtained by the MDOM and the DOM are compared. In the hot-boundary case, the ray effect caused by the DOM is more obvious for the cases with a smaller width of hot boundary, while the MDOM may remedy ray effects and generate more accurate results in acoustically thin media. Furthermore, the MDOM predicts the velocity of phonon transport more accurately than the DOM does. However, the MDOM takes much more computational time as the simulation time or the acoustically thickness increases. From the results, we have seen that it is suitable to use the MDOM in all range of acoustic thickness, especially in acoustically thin media or the case with a smaller width of hot boundary for shorter simulation time. In the heat-source case, the DOM with approximation returns acceptable results for the situations with longer duration of heat source and a larger acoustical thickness; however, in acoustically thin media, the MDOM with S8 approximation is the better choice. In conclusion, the MDOM with S8 approximation returns satisfying results in all range of acoustic thickness or different duration of heat source; however, it is more suitable to be used in acoustically thin media or shorter simulation time.

Oxide heterostructures are attracting huge interest in recent years due to the special functionalities of quasi two-dimensional quantum gases. In this thesis, the electronic states at the interface between perovskite oxides and pyrite compounds have been studied by first-principles calculations based on density functional theory. Optimization of the atomic positions are taken into account, which is considered very important at interfaces, as observed in the case of LaAlO3/SrTiO3. The creation of metallic states at the interfaces thus is explained in terms of charge transfer between the transition metal and oxygen atoms near the interface. It is observed that with typical thicknesses of at least 10-12 °A the gases still extend considerably in the third dimension, which essentially determines the magnitude of quantum mechanical effects. To overcome this problem, we propose incorporation of highly electronegative cations (such as Ag) in the oxides. A fundamental interest is also the thermodynamic stability of the interfaces due to the possibility of atomic intermixing in the interface region. Therefore, different cation intermixed configurations are taken into account for the interfaces aiming at the energetically stable state. The effect of O vacancies is also discussed for both polar and non-polar heterostructures. The interface metallicity is enhanced for the polar system with the creation of O vacancies, while the clean interface at the non-polar heterostructure exhibits an insulating state and becomes metallic in presence of O vacancy. The O vacancy formation energies are calculated and explained in terms of the increasing electronegativity and effective volume of A the side cation. Along with these, the electronic and magnetic properties of an interface between the ferromagnetic metal CoS2 and the non-magnetic semiconductor FeS2 is investigated. We find that this contact shows a metallic character. The CoS2 stays quasi half metallic at the interface, while the FeS2 becomes metallic. At the interface, ferromagnetic ordering is found to be energetically favorable as compared to antiferromagnetic ordering. Furthermore, tensile strain is shown to strongly enhance the spin polarization so that a virtually half-metallic interface can be achieved, for comparably moderate strain. Our detailed study is aimed at complementing experiments on various oxide interfaces and obtaining a general picture how factors like cations, anions, their atomic weights and elecronegativities, O vacancies, lattice mismatch, lattice relaxation, magnetism etc play a combined role in device design.

博士
國立成功大學
土木工程學系
106
A three-dimensional (3D) asymptotic theory is reformulated for the structural analysis of simply-supported, isotropic and orthotropic single-layered nanoplates and graphene sheets (GSs). Eringen’s nonlocal elasticity theory is used to capture the small length scale effect on the static behaviors of these. The interactions between the nanoplates (or GSs) and their surrounding medium are modelled as a two-parameter Pasternak foundation. The perturbation method is used to expand the 3D nonlocal elasticity problems as a series of two-dimensional (2D) nonlocal plate problems, the governing equations of which for various order problems retain the same differential operators as those of the nonlocal classical plate theory (CPT), although with different nonhomogeneous terms. Expanding the primary field variables of each order as the double Fourier series functions in the in-plane directions, we can obtain the Navier solutions of the leading-order problem, and the higher-order modifications can then be determined in a hierarchic and consistent manner. Therefore, some benchmark solutions for the static analysis of isotropic and orthotropic nanoplates and GSs subjected to sinusoidally and uniformly distributed loads are given to demonstrate the performance of the 3D nonlocal asymptotic theory. The nonlocal elasticity solutions of the natural frequency parameters of nanoplates and GSs with and without being embedded in the elastic medium and their corresponding through-thickness distributions of modal field variables are given to demonstrate the performance of the 3D asymptotic nonlocal elasticity theory. The nonlocal elasticity solutions of the critical load parameters of simply-supported, biaxially-loaded single-layered nanoplates and graphene sheets with and without being embedded in the elastic medium are given to demonstrate the performance of the 3D asymptotic nonlocal elasticity theory.

A new frontier of research at the interface of material science and mechanics of solids has emerged with the current focus on the development of nanomaterials such as nanotubes, nanowires and nanoparticles. As the dimensions of a structure approach the nanoscale, its properties can be size-dependent. The classical continuum theory, however, does not admit an intrinsic size, and is not applicable to the analysis of nanoscale materials and structures. Mechanics of nanomaterials-based composites can be understood by incorporating the effects of surface and interfacial energy. A fundamental problem in the study of behaviour of such materials is the examination of size-dependent elastic field of an elastic matrix with nanoscale inhomogeneities. Classical inhomogeneity problems have a rich history since the celebrated work of Eshelby. However, the classical solutions cannot be applied to study nanoscale inhomogeneity problems and new solutions accounting for surface/interface energy have to be derived. This thesis therefore presents an analytical scheme and a finite element formulation to study the size-dependent elastic field of an elastic matrix containing two-dimensional nanoscale inhomogeneities. The Gurtin-Murdoch surface/interface elasticity model is applied to incorporate the surface/interface energy effects. By using the complex potential technique of Muskhelishvili, a closed-form analytical solution is obtained for the elastic field of a nanoscale circular inhomogeneity in an infinite matrix under arbitrary remote loading and a uniform eigenstrain. In the case of an elliptical inhomogeneity, the analytic potential functions are obtained approximately. A new finite element formulation that takes into account the surface stress effects is presented. Elastic field is found to depend on the characteristic dimensions of the inhomogeneity, surface elastic constants and surface residual stress. A striking feature of the new solutions is the existence of singular elastic fields below some dimensions of the inhomogeneity. This phenomenon requires careful further investigation. Eshelby tensor of a nanoscale circular inhomogeneity in an infinite matrix due to a uniform eigenstrain is uniform but becomes size-dependent; however, the tensor is size-dependent and non-uniform in the case of an elliptical inhomogeneity.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

碩士
中原大學
機械工程研究所
104
A Fuzzy-PID controller was proposed design in this paper for a nanoscale platform positioning system. The target nanoscale X-Y platform is mounted on a pantograph mechanism and restricts the rotation by two small sliders , and is driven by a traditional X-Y platform with common precision. The goal of this study is to drive the target platform to move in the region of 20mm  20mm for the positioning, and repeatedly positioning accuracy error is less than 800 nm by the traditional X-Y platform. Due to the different PID parameters will affect platform positioning accuracy and system response for the two axes, the Fuzzy-PID controller were training to fit the mechanism to promote the positioning precision and path control effect. The simulation and experimental results indicated that the proposed method is feasible for the nano-scale micro-platform positioning.

碩士
國立臺灣科技大學
機械工程系
100
The quasi-steady molecular statics orthogonal nanocutting model of single-crystal silicon developed by the paper not only can calculate the cutting force, equivalent stress and equivalent strain, but also can calculate the temperature rise of the cut workpiece, and furthermore, can analyze the temperature distribution of the cut workpiece. The paper supposes that the temperature rise of the cut workpiece during orthogonal nanocutting is produced by two heat sources, namely plastic deformation heat and friction heat. The calculation method of equivalent stress and equivalent strain of single-crystal silicon developed by the paper is the use of three-dimensional quasi-steady nanostatics nanocutting model to simulation calculation. The paper applies the concept of force balance, and Hooke-Jeeves search method to solve the force balance equation, solve the newly displaced position of each atom of the cut workpiece, and then calculate the shape of chips and size of cutting force during cutting. After the position where the atoms are deformed and displaced is acquired, and employing the paper’s finite-element shape function concept, the paper develops cutting of single-crystal silicon material. Atoms are regarded as nodes, and lattices are regarded as elements. The paper conducts numbering of each node in the single-crystal silicon, and carries out cutting of lattices. The paper cuts lattices into 36 constant -strain tetrahedron, and conducts numbering of each of the cut lattices. Then the three-dimensional equivalent strain of the cut workpiece can be obtained. Using the flow stress-strain relational equation acquired after regression treatment of stress-strain curve in nanoscale thin-film tensile numerical experiment, the paper uses flow curve to calculate the equivalent stress produced under equivalent strain of elements. The flow deformation heat developed by the paper can be calculated by the equivalent stress and equivalent strain of the single-crystal silicon workpiece being cut. Furthermore, the paper develops the calculation method for temperature rise of the cut workpiece produced by flow deformation heat. Besides, the paper additionally develops the method of friction heat produced by workpiece atoms on the tool flank performing orthogonal nanocutting of single-crystal silicon, and the calculation method of temperature rise of workpiece atoms on tool flank. Regarding these methods, Morse force is decomposed to be friction force on tool flank, and the heat produced from the power of friction force is calculated. Such heat is then distributed to workpiece atoms on tool flank and to atoms of cutting tool. Furthermore, the numerical value of temperature rise of workpiece atoms on tool flank is calculated. The temperature rise produced from those two heat sources are added up, and the total temperature rise of the various atoms of the cut single-silicon workpiece can be obtained for making analysis of temperature field. Besides, the paper also further substitutes the total temperature rise of the various atoms of the cut single-crystal silicon workpiece in the three-dimensional finite-difference heat transfer equation in order to perform heat transmission. It refers that the workpiece temperature, calculated by substituting the numerical value of total temperature produced at each step in the heat transfer equation, is just the initial temperature of workpiece at the next step. This method is used to calculate the temperature field of the single-crystal silicon workpiece having undergone orthogonal nanocutting at each step, and further analysis is made. Finally, comparison is made with the numerical values of temperature rise of the various atoms of the cut single-crystal silicon workpiece being calculated above without consideration of finite-difference heat transfer.

博士
國立交通大學
材料科學與工程系所
96
Material with nanometer-scale size have large ratio of surface to bulk atoms. Large surface always gives high active behavior and changes in both physical and chemical properties. Nanomaterials such as nanoparticles, nanotubes, nanorods and nanowires having size generally smaller than 100nm exhibit superior photoelectronic and magnetic properties in various applications. Therefore, in this thesis, the studies will be focused on the synthesis, structure analysis and property characterization of zero-/one dimensional nanoscaled materials. In chapter 2, ZrO2, TiO2, ZnO and Al2O3, were chosen as raw materials to synthesize a target for laser ablation. The formed nanoparticles exhibit two kinds of particle size distribution with 7~15 nm (70~90%) and 40~100 nm (10~30%). Nanoparticles synthesized at lower fluence laser ablation are rich in Zn composition and show more narrow distribution. While increasing laser fluence, the composition of the collected nanoparticles is primarily composed of Zr. A model based on composition and morphology of both nanoparticles and target with changing laser fluence was proposed to explain the phase evolution of nanoparticles. The average far-infrared emissivity of the nanoparticles based on ZrTiO4--ZnAl2O4 system is measured to be more than 80﹪(wavelength range from 4 to 12 μm) and varies with crystal phase ratio. In chapter 3, a highly dispersed nano-TiO2/Ag catalyst is synthesized in an alkaline solution. Nearly all of the dimethy-blue target pollutant at high concentration was removed when the photoreaction was performed in a short period. This novel nano TiO2 photocatalyst exhibits excellent photocatalytic activity because it is well dispersed. Since no dispersant or organic binder was used, this synthetic process has the advantages of low cost and convenience. In chapter 4, One-dimensional nanotube arrays of nickel-phosphate have been developed by electroless deposition into sub-micro to nanometer sized pores of the porous alumina templates. The dimension of the formed nanotubes has 1μm in length, 200~300nm in diameter and 80~150nm in thickness of tube walls. Transmission electron microscopy examination of the nanotubes clearly show amorphous hallow structure with a average grain size of ~5 nm. The hysteresis loops of the nanotube arrays show a coercive field of about 200Oe under treatment in 95%N2/5%H2 atmosphere at 500 oC as the magnetic field was applied along parallel and perpendicular to tube axis. The nanotube arrays also exhibit an anisotropic magnetic property with easier saturation along the perpendicular direction. However, both coercive field and saturation of remanent magnetization of the nanotube arrays become lower while continually increasing heat treatment temperature up to 900oC. In chapter 5, ordered silver- nickel core-shell nanowire arrays were successfully fabricated by electrodeposition. The ordered silver nanowire arrays embedded in a porous alumina template were first fabricated from an aqueous solution of Ag(NO3)2 and Ac(NH3). After removing out the template, the obtained silver nanowire arrays were subsequently electrodeposited with nickel at 1.6~2.6V and 60oC using the electrolyte composed of NiSO4, NiCl2 and H3BO3. Transmission electron microscopy (TEM) observation reveals that a 15 nm thick nickel film was coated on the surface of the silver nanowires with about 200 nm in diameter. It was found that the silver nanowires with nickel coating showed enhanced magnetic properties in comparison to that of pure silver nanowires. The Magnetic Force Microscope (MFM) image of silver- nickel core-shell nanowires exhibits magnetic domain state. In addition, the hysteresis loops of the silver-nickel nanowire arrays show a coercive field of 180Oe, almost independent of the applied magnetic field parallel and perpendicular to nanowires. However, it was observed that a larger magnetic domain was found in parallel direction than that in perpendicular direction. In chapter 6, a single bath electrodeposition method was developed to integrate nanowires of Ag/Co with multi-layer structures within a commercial AAO (anodic alumina oxide) template, with a pore diameter 100~200 nm. An electrolyte system containing silver nitride and cobalt sulfide was explored by using cyclic-voltammetry and electrodeposition rate to optimize electrodeposition conditions. A designed step-wise potential and different cations ratio [Co2+] / [Ag+] were adopted for the electrodeposition. After dissolution by NaOH, Ag/Co multilayered nanowires were obtained with a composition {[Co]/[Ag80Co20]}30 identified by XRD and TEM when [Co2+] / [Ag+] = 150. By annealing at 200oC for 1hr, the uniformly structured {Co99.57/Ag100}30 nanowires were obtained. Compared with pure Co nanowire, the magnetic hysteresis loops showed manifest magnetic anisotropy for {Co99.57/Ag100}30 nanowires than that of pure Co nanowires corresponding to a change of easy axis upon magnetization. In chapter 7, The heterojunction photovoltaic devices consist of hybrid p-type organic Cu-phthalocyanine and inorganic n-type semiconductor ZnO nanostructures which include vertically aligned nanorods, randomly oriented nanorods and nanoparticles. The strong absorption of ZnO appears in 250~460nm wavelength and Cu-phthalocyanine exhibits broad absorption in 440-700nm with an absorption maximum at 630nm. The incorporation of partial Al into ZnO leads to the shift of absorb light from UV region to visible light and subsequently causes more charge generation. Charge recombination from hybrid devices of vertically aligned ZnO nanorods was more efficient than that fabricated from the other types. The maximum incident photon to electron conversion and energy conversion efficiencies under simulated sunlight AM1.5 (10mW/cm2) in aligned ZnO are 0.036mA and 1.32%, respectively. In chapter 8, a new 1 and 2 dimension nano structure for making solar cell or TFT module have been researched by adopting low cost coated glass substrate with polysilicon instead of silicon wafer. Meanwhile, laser annealing is used as the unique method to melt primal amorphous silicon thin film and promote it recrystalize under low temperature. Particularly, the new thermal conducting layers are patterned under the silicon layer to enhance the lateral giant grain growth. The important processes are represented as follows: 1. A electrical conducting layer are formed on the glass substrate. 2. Photolithographic process is executed to pattern the thermal conducting layer and form many variable thermal conducting zone. 3. An about 200nm amorphous silicon film is formed on the patterned thermal conductive layer. 4. A thermal isolation layer such as SiO2 is deposited for keeping laser annealing temperature. 5. While the pulse excimer laser is injected the structure, the amorphous silicon film can absorb laser energy instantaneously and transform it to crystalline type. Moreover, the temperature gradient could be generated on the silicon layer and cause the uniform polysilicon growth of 1~2μm giant grains under about 450-475mJ/cm2 laser fluence. A unique method of multiple laser fluence have been executed to increase the crystalline orientation of Si(111).

碩士
嘉南藥理大學
應用空間資訊系
106
A study of nanoscale aluminum powder applied on the laser powder bed fusion additive manufacturing process by the molecular dynamics simulation method performed. Three nanoscale aluminum powders with different geometric shape selected and utilized to explore the morphological effect. Morphology of aluminum powder includes solid sphere, hollow sphere, and solid ellipsoid. Various diameters of solid sphere powder made up to six study cases, and similar combinations applied to hollow sphere powder, as well. Moreover, four types of solid ellipsoidal powder, such as parallel, skew, end-to-side, and side-to-side was composed to twelve study cases. Heating rates were properly monitored and analyzed auxiliary conditions such as neck width, potential energy, and gyration radius to observe the coalescence and melting temperature of nanoscale aluminum in the room temperature environment or high-temperature laser sintering process. Results reviled the solid state sintering automatically took place at room temperature in case of solid spherical, hollow spherical, or solid ellipsoidal aluminum powder. In constant nanoscale size sintering process, the coalescence and melting temperature of nanoscale aluminum powder decreased with shrinking size or the reducing number of atoms. On the other hand, the coalescence and melting temperature of nanoscale aluminum rose with increasing the heating rate in the constant heating rate. In thermal equilibrium or high-temperature laser sintering process, the parallel type with a largest value of neck width, while that value of end-to-end type was the smallest for solid ellipsoidal aluminum powder. Outcome also demonstrated the size of powder dominated meting temperature; melting point of nanoscale aluminum is significantly lower than macroscopic aluminum. In this study, metallic powder particle size and heating rate obviously affect the physical properties of additive manufacturing, the geometries and morphologies of nanoscale metallic powder play another effective role to the process.

Tesis (Doctor en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2015.
Esta tesis está dedicada al estudio teórico del grafeno iluminado por un láser intenso. Nos enfocamos en efectos no perturbativos de la luz sobre el material, utilizando la teoría de Floquet. Mostramos cómo un láser puede modificar la estructura electrónica del grafeno, alterando sus propiedades de conducción, y generando también características topológicas de otra manera ausentes en el material no iluminado. Verificamos la existencia de estados topológicos de Floquet con cálculos espectrales y de los invariantes topológicos, dándole especial importancia al caso más realista y más complejo de radiación bajas frecuencias.

Tesis (Doctor en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2017.
Los descubrimientos experimentales del grafeno y de los materiales aislantes topológicos han suscitado un gran interés en la comunidad científica. El objetivo de la presente tesis es estudiar los estados topológicos de borde del grafeno y otros materiales de baja dimensión, y analizar diferentes formas de manipulación y dirección de los mismos para obtener sistemas con nuevas propiedades. Para ello, empleamos como base el modelo SSH para polímeros conductores (presenta carácter topológico nativo), y el grafeno. A este último se le inducen propiedades topológicas a partir de perturbaciones externas como ser campos magnéticos, términos de acoplamiento de tipo Haldane o irradiación con luz láser (teoría de Floquet). Entre los resultados encontrados podemos destacar la posibilidad de destruir y crear selectivamente estados de borde topológicos, y de dirigir la corriente eléctrica a través de los mismos. Estos efectos resultan atractivos para el diseño de futuros nanodispositivos y sus posteriores aplicaciones.
The experimental discoveries of graphene and topological insulator materials have aroused great interest in the scientific community. The aim of this thesis is to study the topological edge states of graphene and others low dimensional materials, and to analyze different ways of manipulating and directing them to achieve systems with new properties. In order to do this, we employ the SSH model for conducting polymers (it has a native topological character) and graphene as a base. Topological properties are induced to the latter through external perturbations such as magnetic fields, Haldane coupling terms or irradiation with laser light (Floquet theory). Among the results found we can highlight the possibility of selectively destroying and creating topological edge states, and of directing the electrical current through them. These effects are attractive for the design of future nanodevices and their subsequent applications.