The quality of GaN template layer plays a very important role in high electron mobility transistors. We proposed a special method in the growth of molecular beam epitaxy to deal with the dilemma between structure and the morphology of GaN. In our study, we used a nitrogen-rich GaN growth condition to deposit the initial varied layer. After that, we changed the N/Ga ratio stepwise to the growth condition of gallium-rich GaN and grew the epitaxy layer right away. In X-ray diffraction analysis, the full width at half-maximum (FWHM) value of rocking curves of GaN(002) was improved relatively to gallium-rich sample from 531.69 arcsecond to 59.43 arcsecond. In atomic force microscopy (AFM) analysis, the root mean square (rms) roughness of sample surface was improved relatively to nitrogen-rich sample from 18.28 nm to 1.62 nm over 5 £gm ¡Ñ 5 £gm area. The Raman scattering shows there is a slightly tilted plane in gradient layer and the gradient layer can also slash the strain force which is caused from Ga-rich GaN epitaxy layer and AlN buffer layer. A series high mobility AlxGa1-xN/GaN heterostructures samples were grown on MOVPE-grown GaN templates substrate by molecular beam epitaxy with different Al concentrations (x = 0.017~0.355). The quality checked by XRD and AFM indicated that the excellent properties agreed with the GaN-template. The highest mobility in this series samples at 8 K is 19593 cm2/Vs with carrier concentration 3.13 ¡Ñ 1012 cm-2 and Al concentration x = 0.017. In our experiments, the carrier density decreases as Al concentration reduces. In the illuminated Hall measurement, there are only few electrons increased following blue LED illumination. It shows that there are only few deep level defects existing near the heterointerface. From temperature-depended Shubnikov-de Haas (SdH) oscillations, the electron effective mass m* in 2DEG are evaluated as 0.213 mo and for x = 0.207 0.227 moand 0.136 respectively. The high mobility AlxGa1-xN/GaN was fabricated to a series of wires by focused ion beam (FIB) equipment, and the width of the active channel is ranged from 900 nm to 50 nm (900 nm, 500 nm, 300 nm, 200 nm, 100 nm, 80 nm and 50 nm) with the channel orientation in [11 0] direction. The largest spin-splitting energy in the series of wires is 2.14 meV. Due to larger spin-splitting energy and quasi-ballistic transportation, the 200 nm wire is the best candidate to be the channel of the quantum-ring interferometer in our case.

FIB is currently the economic methods to produce nano-structure below 100nm. In the past, FIB manufactures nano-structure patterns also unsatisfactory. In this study, the influence of twice deposited mask layer on the aspect ratio of nano-structure and verticality of side wall contour was discussed. The single mask layer is used for pattern transfer. Pattern distortion may occur during etching due to several factors like improper parameter setting, limitation of machine table, etc. The most common situations are aciculate and salient shape on the top and angle of slope which is too big to be vertical. In order to improve above-mentioned situations, a mask layer of multi-deposition was designed to protect the side wall so that it could retard etching. In addition to modifying verticality of side wall, the aspect ratio could be raised indirectly because the second deposition had reduced the interval between patterns. In the aspect of using machine table, the first mask layer, chromium, which was deposited by the sputtering machine. And the etching pattern was directly written on the first mask layer by focused ion beam. The silicon was uncovered at etched place, and then the second mask layer, silica (SiO2), which was deposited by the sputtering machine. The surface contour was directly covered with silica layer. Right after that, the top and bottom of silica were removed through vertical etching by inductively coupled plasma machine. The silica on the side wall of structure was retained to protect the side wall and raise aspect ratio. Eventually, the silicon was etched by the same way of inductively coupled plasma machine that it was researched on the difference in etching gas. And there was a comparison between chlorine and fluorine gases. After optimizing parameters, the nano-structure was made under 100nm.

Interest in the fabrication of nano-optical structures has increased dramatically in recent years, due to advances in lithographic resolution. In particular, metallic nanostructures are of interest because of their ability to concentrate light to well below the diffraction limit. Such structures have many potential applications, including nanoscale photonics, quantum information processing and single molecule detection/imaging. In the case of quantum computing and quantum communication, plasmon-based metal nanostructures offer the promise of scalable devices. This is because the small optical mode volumes of such structures give the large atom-photon coupling needed to interface solid-state quantum bits (qubits) to photons. The main focus of this dissertation is on fabrication and testing of surface plasmon-based metal nanostructures that can be used as optical wires for effciently collecting and directing an isolated atom or molecule's emission. In this work, Ag waveguides having 100nm£50nm and 50nm£50nm cross sections have been fabricated ranging from 5¹m to 16¹m in length. Different types of coupling structures have also been fabricated to allow in-coupling and out-coupling of free space light into and out of the nanometric waveguides. The design of waveguides and couplers have been accomplished using a commercial finite difference in time domain (FDTD) software. Different nanofabrication techniques and methods have been investigated leading to robust and reliable process conditions suitable for very high aspect ratio fabrication of metal structures. Detailed testing and characterization of the plasmon based metal waveguides and couplers have also been carried out. Test results have revealed effective surface plasmon propagation range. 0.5dB/¹m and 0.07dB/¹m transmission losses have been found for 100nm and 50nm wide waveguides respectively, which correspond to 1/e propagation lengths of 9¹m and 60¹m. Input coupling effciency was found to be 2% and output coupling effciency was found to be 35%. The fabrication and testing results presented provide critical demonstrations to establish the feasibility of nanophotonic integrated circuits, scalable quantum information processing devices, as well as other devices, such as single molecule detectors and imaging systems.

Transparent conductive aluminum-doped zinc oxide(AZO) thin films were synthesized by reactive RF magnetron co-sputtering system with metallic zinc and aluminum targets under oxygen atmosphere. Systematic study on the fixed sputtering power of the Zinc target (PZn) and the variation of the sputtering power of the Aluminum target (PAl) on structural, electrical and optical properties of AZO thin film was mainly investigated in this work. We found that the microstructure of AZO films would be obviously transformed from rice-like crystalline structure to nanocrystalline (nano-column) structure with the increasing of the sputtering power of the Aluminum target (PAl) . Nanocrystalline AZO films were formed at the specific sputtering power ratio of metallic targets (PAl/ PZn=1) . X-ray diffraction (XRD) spectra revealed that nanocrystalline AZO films highly preferred c-axis orientation (002) was growth in perpendicular to the substrate. The optical refractive index (n) of nanocrystalline AZO films had significantly lower values than others of microstructure AZO films, and this suggested the low optical dispersion in nano-column structure . Furthermore, the electronic properties of AZO films with the proper sputtering power of the Aluminum target (PAl) evidently improved under rapid temperature annealing (RTA) process. It suggested that both high annealing temperature(400¢J) and rapid cooling time(15min) are main factors to decrease the sheet resistances due to the maintenance of high temperature structural phase. The results of X-ray photoelectron spectroscopy (XPS) show that RTA process can decrease oxidized Al in order to decrease the sheet resistances.

The surface phenemona in polishing process induced by nano-particle was studied in this thesis. The properties of particle, rigidity and geometry, are forced. A perfect polished surface includes lower roughness and thinner damage layer. Besides a perfect surface, how we get higher rate of remove is also an important thing. The goal is to get the relation between induced surface phenomena and properities of nano-particle. The M.D. (Molecular Dynamic) simulation is uesed in this thesis. The specicaly lowered integral timestep is second for simulating the rigidity of nano-particle with saving simulation time and geting accurate in simulation results. In order to simuate the nano-particle rigidity and adhesive effects between nanoparticle and work surface, the modified potential function is used. Considering the types of nano-particle motion which are pure rolling and sliding, the different geometric shapes are used . In the results of simulation about the rigidity of particles, the phenomena induced by rolling particles and rigidity don¡¦t have apparent correlation. For sliding particles, the lower rigidity and lower thick damage layer was. However, if the rigidity is too weak to hold the particle geometric shape, the damage layer thickness is larger. In the results of simulation about particle shapes, the sliding particle with larger front angle will indcue deeper damager layer. It¡¦s because the more workpiece atoms could move to the bottom or rear of the particles to make more damaged atoms. If the length of particle bottom be increased, the interactive behavior between particle and work surface would become more violently to make deeper damaged layer. The rolling particle with scraggy surface can cohere more atoms than the ball particle even in the lower adhesive coefficient, but induced roughness will be higher .

In this thesis, we study the electrical characteristics of a series of polysilicon thin-film transistors (poly-Si TFTs) with different numbers of multiple channels of various widths, with lightly-doped drain (LDD) structures. Among all investigated TFTs, the nano-scale TFT with ten 67 nm-wide split channels (M10) has superior and more uniform electrical characteristics than other TFTs, such as a higher ON/OFF current ratio (>109), a steeper subthreshold slope (SS) of 137 mV/decade, an absence of drain-induced barrier lowering (DIBL) and a suppressed kink-effect. These results originate from the fact that the active channels of M10 TFT has best gate control due to its nano-wire channels were surrounded by tri-gate electrodes. Additionally, experimental results reveal that the electrical performance of proposed TFTs enhances with the number of channels from one to ten strips of multiple channels sequentially, yielding a profile from a single gate to tri-gate structure. In addition, we have also studied the multi-gate combining the pattern-dependent nickel (Ni) metal-induced lateral crystallization (Ni-MILC) polysilicon thin-film transistors (poly-Si TFTs) with ten nanowire channels. Experimental results reveal that applying ten nanowire channels improves the performance of Ni-MILC poly-Si TFT, which thus has a higher ON current, a lower leakage current and a lower threshold voltage (Vth) than single-channel TFTs. Furthermore, the experimental results reveal that combining the multi-gate structure and ten nanowire channels further enhances the entire performance of Ni-MILC TFTs, which thus have a low leakage current, a high ON/OFF ratio, a low Vth, a steep subthreshold swing (SS) and kink-free output characteristics. The multi-gate with ten nanowire channels NI-MILC TFTs has few poly-Si grain boundary defects, a low lateral electrical field and a gate channel shortening effect, all of which are associated with such high-performance characteristics. The PDMILC TFTs process is compatible with CMOS technology, and involves no extra mask. Such high performance PDMILC TFTs are thus promising for use in future high-performance poly-Si TFT applications, especially in AMLCD and 3D MOSFET stacked circuits. Otherwise, we have investigated the mechanism of the leakage currents in polysilicon TFT with different temperature and applied biases. Moreover, we have simulated the electric fields in different structure polysilicon TFT to explain the mechanism of the leakage currents. By comparing the leakage currents in different channel structures, the leakage current in nanowire channel structure is higher than that in non-nanowire channel structure. Moreover, the leakage current in multiple gate structure is lower than that in single gate structure. Therefore, these two experimental results are caused by high electric field in the drain-to-gate overlap and drain-to-body depletion region respectively.

The mechanical properties of the amorphous bulk metallic glassy (BMG) alloy, Mg58Cu31Y11, are examined by a non-traditional analytic method - nanoindentation scratch test. This thesis will discuss the influences of friction force, and fracture surface geometry on the BMG surface for load, depth of scratch, scratch velocity, and test temperature of the nano-scratch process. In this study, experimental factors, including load, depth of scratch, scratch velocity, and test temperature, are taken into consideration to investigate the effects of the friction force. And then, this research utilizes regression analysis to establish BMG machining experience formula. The significant parameters of the friction force on nano-scratch and the reliability of the prediction model are investigated by statistical software. According to the results, the friction force is nearly proportional to power of the load. The friction force exhibits a slightly dependence on the test temperature. Besides, the nano-scratch results show that the friction coefficient also increases as the load and test temperature increases. The results associated with the analysis of the variance can be practiced to assess the prominence among experimental factors. The analysis indicates that the load, test temperature play significant factors on the friction force. The results of the regression analysis using a statistical software can be applied to model the mathematical relationship between machining factors and friction force. It anticipates that the model is able to predict friction force over a wide variety of scratching conditions. The model is also proved in good agreement with experimental results.

Cette thèse, effectuée dans le cadre du projet Européen MEDEA+, PICS, porte sur la conception d'imageurs CMOS destinés aux applications de sécurité automobile et de surveillance. Le travail s'est focalisé sur l'amélioration de la dynamique de fonctionnement des imageurs CMOS tout en conservant des valeurs de bruit spatial fixe, une consommation et une surface de pixel minimales. Plusieurs solutions ont été explorées, les pixels à compresseur logarithmique, les pixels à temps d'intégration et les pixels intégrant une adaptation aux conditions lumineuses. Ces études ont abouties à la conception et la fabrication de quatre imageurs CMOS. Ces capteurs ont été testés et ont permis de valider les approches choisies.

Manipulating electromagnetic fields with plasmonic nanostructures has attracted researchers from interdisciplinary areas and opened up a wide variety of applications. Despite the intriguing aspect of inducing unusual optical properties such as negative indices and indefinite permittivity and permeability, engineered plasmonic nanostructures are also capable of concentrating electromagnetic waves into a diffraction-unlimited volume, thus induce incredible light-matter interaction. In this dissertation, I’ll discuss about a class of plasmonic structures that exhibit the Fano resonance. The Fano resonance is in principle the interference between two resonant modes of distinct lifetimes. Through the Fano resonance, the electromagnetic energy can be trapped in the so called “dark” mode and induce strong local field enhancement. A variety of Fano resonant nanostructures ranging from periodic planar arrays to simple clusters composed of only two particles are demonstrated in this dissertation. By artificially designing the dimensions of the structures, these Fano-resonant materials can be operated over a broad frequency range (from visible to mid-IR) to target the specific applications of interest. In this dissertation, I’ll show the following research results obtained during my PhD study: (1) the double-continuum Fano resonant materials that can slow down the speed of light over a broad frequency range with little group velocity dispersion. (2) Ultra-sensitive detection and characterization of proteins using the strong light-matter interaction provided by the Fano-reonant asymmetric metamaterials. (3) Metamaterials absorbers with nearly 100 % absorbance, tunable spectral position, expandable bandwidth, and wide angle absorption. These Fano-resonant materials can have profound influences in the areas of optical signal processing, life science, bio-defense, energy harvesting and so on. / text

Metals interact very differently with light than with radio waves and finite conductivities and losses often limit the way that RF concepts can be directly transferred to higher frequencies. Plasmonic materials are investigated here for various optical applications, since they can interact, confine and focus light at the nanoscale; however, regular plasmonic devices are severely limited by frequency dispersion and absorption, and confined signals cannot travel along plasmonic lines over few wavelengths. For these reasons, novel concepts and materials should be introduced to successfully manipulate and radiate light in the same flexible way we operate at lower frequencies. In line with these efforts, optical metamaterials exploit the resonant wave interaction of collections of plasmonic nanoparticles to produce anomalous light effects, beyond what naturally available in optical materials and in their basic constituents. Still, these concepts are currently limited by a variety of factors, such as: (a) technological challenges in realizing 3-D bulk composites with specific nano-structured patterns; (b) inherent sensitivity to disorder and losses in their realization; (c) not straightforward modeling of their interaction with nearby optical sources. In this study, we develop a novel paradigm to use single-element nanoantennas, and composite nanoantenna arrays forming two-dimensional metasurfaces and three-dimensional metamaterials, to control and manipulate light and its polarization at the nanoscale, which can possibly bypass the abovementioned limitations in terms of design procedure and experimental realization. The final design of some of the metamaterial concepts proposed in this work was inspired by biological species, whose complex structure can exhibit superior functionalities to detect, control and manipulate the polarization state of light for their orientation, signaling and defense. Inspired by these concepts, we theoretically investigate and design metasurfaces and metamaterial models with the help of fully vectorial numerical simulation tools, and we are able to outline the limitations and ultimate conditions under which the average optical surface impedance concept may accurately describe the complex wave interaction with planar plasmonic metasurfaces. We also experimentally explore various technological approaches compatible with these goals, such as the realization of lithographic single-element nanoantenna and nanoantenna arrays with complex circuit loads, periodic arrays of plasmonic nanoparticles or nanoapertures, and stacks of rotated plasmonic metasurfaces. At the conclusion of this effort, we have theoretically analyzed, designed and experimentally realized and characterized the feasibility of using discrete metasurfaces to realize phenomena and performance that are not available in natural materials, oftentimes inspired by the biological world. / text