In this thesis, the growth and fabrication of the self-assembly ordered porous alumina have been investigated. First, well-ordered honeycomb array can be obtained in large area under well-anodizing condition. The diameter of formed porous alumina was about 40 to 80 nm. Pore diameter can be tuned by different voltage and electrolyte. After we got such an ordered-arrangement porous alumina array, the following analysis of the material optical properties were characterized. In the luminescence behavior, photoluminescence (PL) measurements showed a strong PL peak in blue. The PL peak was at 420 nm excited by He-Cd laser. Material transmittance was also detected, the result showed that material was transparent above 400 nm. On the other hand, the porous alumina membrane can be used as a mask. For working as negative mask, we evaporated the metal such as Au or Ti into the membrane and the metal filled into the porous to adhere to the semiconductor substrate. After lifting-off the membrane, the metal nanadots was formed on the substrate. The size and the position of these metal nanodots were distinctly-controlled by the mask. For working as replica mask, we have used the membrane as an etching mask to transfer the pattern to the semiconductor substrate successfully. This technique has the advantages of low cost and large area for nano-fabrication.

Abstract The AAO membrane with nanopore arrays were fabricated by anodizing highly pure aluminum foils (99.9995%) in electrolyte under steady voltage. Pore diameter can be controlled by different anodic voltage(from 30 to 50 V) and electrolyte, on the other hand, thickness is proportioned to anodizing time , and interpore could follow this rule(a = 15.4+2.63¡Ñv) , and minimum radius of pore could reach 15nm . The XRD spectra of AAO without and with annealing, both showed the diffraction peaks of (311)¡B(400)¡B(440), corresponding to the £^-Al2O3 phase . Before fabricating AAO, we would polish under low temperature and then clean alumina foil in order to reduce surface roughness that is good for better order and regular. Through the use of porous anodic alumina masks, Au nanodot arrays deposited on Si by E-gun with AAO mask. Subsequently, the AAO mask was removed by H3PO4. Under the same procedure, we can fabricate 80nm of the diameter of pore and apply this mask on wafer of laser constructure . Because of regular hexagonal pore array, we may get the photonic crystal effect. During PL experiment, we got the result that AAO could increase light extraction of quantum dot from C237 wafer and controlled emission peak from C238 and C196 wafer and position of peak could shift to 1140nm. We hope nanodot array on wafer of laser structure could control emission peak.

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

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

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

GaN nanopore arrays with pore diameters of approximately 75 nm were fabricated by inductively coupled plasma etching (ICP) using anodic aluminum oxide (AAO) films as etch masks. Nanoporous AAO films were formed on the GaN surface by evaporating an Al film onto a GaN epilayer and subsequently anodizing the aluminum. To minimize plasma-induced damage, the template was exposed to CF4-based plasma conditions. Scanning electron microscopy (SEM) analysis shows that the diameter and the periodicity of the nanopores in the GaN were directly transferred from the original anodic alumina template. The pore diameter in the AAO film can be easily controlled by tuning the anodization conditions. Atomic force microscopy (AFM), photoluminescence (PL) and micro-Raman techniques were employed to assess the quality of the etched GaN nanopore surface. Such a cost-effective method to produce nano-patterned GaN template would be useful for growth and fabrication of III-Nitrides based nanostructures and photonic band gap materials. / Singapore-MIT Alliance (SMA)

Dans cette thèse, le concept d’électrochimie bipolaire qui permet de réaliser des réactions électrochimiques par l’application d’un champ électrique, sur un objet conducteur placé dans une solution électrolytique sans aucun contact avec les électrodes, a été utilisé pour générer des objets Janus possédant une partie organique et une partie inorganique. Comme preuve de principe, des billes de carbone vitreux de taille micrométrique ont été modifiées de manière asymétrique par électrochimie bipolaire en réduisant un sel d’aryl diazonium. La couche organique ainsi greffée a pu être observée après interaction avec des nanoparticules d’or, ou des molécules fluorescentes. Les résultats ont montré que la moitié de la surface des billes a pu être modifiée de manière sélective et avec une grande précision. En ajustant le temps et/ou le champ électrique utilisé pour la réduction du sel de diazonium, la surface greffée peut être modulée. Ce concept a été généralisé à l’échelle nanométrique sur des nanotubes de carbone alignés verticalement. Ces nanotubes de carbone ont été préparés par un dépôt chimique en phase gazeuse en utilisant un template d’oxyde d’aluminium poreux. L’électrogreffage bipolaire d’une couche organique uniquement sur une extrémité des nanotubes et uniquement sur la face interne de ces tubes, a été possible en conservant les nanotubes piégés dans le template d’oxyde d’aluminium. Cette technique ouvre donc la voie d’applications dans le domaine des piles à combustible, des bio-capteurs, et également pour la délivrance contrôlée de médicaments. / In this thesis, the concept of bipolar electrochemistry, which allows carrying out electrochemical reactions on a free-standing conductive object in an electric field, was employed to generate Janus-type objects with a hybrid organic-inorganic composition. As a proof-of-concept micrometer-sized glassy carbon beads were modified asymmetrically via the bipolar electrochemical reduction of aryl diazonium salts. The grafted organic layers can be probed either with gold nanoparticles (AuNPs) or with fluorescent molecules. The results show that one-half sphere of the beads was modified selectively and with high precision. This concept was then generalized to vertically aligned carbon nonotubes (VACNTs). They were prepared via chemical vapor deposition using porous anodic aluminum oxide (AAO) as template. The bipolar electrografting of an organic layer onto the inner surface of the VACNTs was performed by using the tubes that were still embedded in the pores of the AAO membrane as the starting material. The grafted results can be visualized by coupling them with AuNPs. After the AAO removal, the results reveal a grafting of organic layers only at one end of the tubes along the inner wall. For both cases, fine tuning of the deposition time and/or the electric field used for the reduction of diazonium salts can control the geometric area of the grafting. This technique opens up applications of these objects in the fields of controlled drug delivery and storage.

Цель магистерской диссертации состояла в изучении влияния режимов анодирования и условий последующей температурной обработки на структурные и люминесцентные свойства нанопористого оксида алюминия. Рассмотрены основные структурные особенности анодированного оксида алюминия (АОА) и методики получения его упорядоченных структур, его области применения и люминесцентные свойства. Успешно синтезирована серия из 20 образцов АОА в условиях варьирования электрохимических, временных и температурных режимов. Проведена аттестация полученных образцов методами сканирующей электронной микроскопии и рентгеноструктурного анализа. Проведена статистическая обработка полученных снимков с помощью анализатора изображений SIAMS 700. Проанализированы зависимости среднего диаметра пор от напряжения анодирования и толщины оксидного слоя от времени анодирования. Рассчитана средняя скорость роста АОА для гальвано- и потенциостатических режимов. Изучены особенности и трансформация спектров диффузного отражения, фото- и катодолюминесценции образцов АОА в зависимости от условий электрохимического окисления и последующей термообработки. На основе сравнительного анализа литературных данных проведена идентификация активных центров свечения собственной (F-, F+-центры) и примесной (комплексы C2O42- и HC2O4-, ионы Cr3+ и Mn4+) природы. Рассмотрены перспективы дальнейших исследований и возможных применений синтезируемых мембран анодированного оксида алюминия. / The aim of this Master paper is to study the effect of anodizing modes and subsequent temperature treatment on structural and luminescent properties of nanoporous anodic alumina. Structural features of anodic aluminum oxide (AAO), its ordered structures obtaining methods, fields of application and luminescent properties were discussed. A series of twenty samples varying electrochemical, time and temperature regimes was obtained. Obtained samples were characterized by scanning electron microscopy and X-ray diffraction analysis techniques. Images of structures were quantitavely analyzed using SIAMS 700 software package. It was studied how average pore diameter and oxide layer thickness depend on anodizing voltage and duration accordingly. Average AAO growth rate for galvanostatic and potentiostaic modes was calculated. Features and transformation of diffuse reflection, photo- and cathodoluminescence of AAO samples obtained under various electrochemical oxidation conditions and after subsequent temperature treatment were studied. Active emission centers of intrinsic (F-, F+-centers) and impurity (C2O42- and HC2O4- complexes, Cr3+ и Mn4+ ions) nature were identified on the basis of literature data comparative analysis. Further promising directions of studies and possible applications of synthesized AAO membranes were discussed.

В работе проведено исследование оптических характеристик коллоидных квантовых точек (КТ) InP/ZnS различных размеров (QD-1, QD-2, QD-3) и композитных наноструктур анодированного оксида алюминия (AAО) с КТ методами спектрофотометрии и люминесцентной спектроскопии. Выполнен литературный обзор, касающийся электронных состояний в идеальном нанокристалле (НК), синтеза КТ на основе InP, использования НК для создания нанокомпозитов и расчёта цветовых характеристик излучателей. Описаны методики подготовки образцов и проведения измерений спектров оптического поглощения (ОП) и фотолюминесценции (ФЛ). По анализу спектров ОП КТ определены значения энергий оптических переходов. Полосы с наименьшей энергией соответствуют первому экситонному пику поглощения ядра InP. Другие могут быть приписаны оболочке из ZnS. По синему сдвигу осуществлена оценка размера ядер образцов КТ. Для QD-1 исследована температурная зависимость первого экситонного пика поглощения. Спектры ФЛ позволяют предположить, что полосы свечения формируются как экситонными переходами, так и дефектами кристаллической решётки ядра InP. Синтезирован ряд структур нанопористого оксида алюминия, отожженного при различных температурах, с осаждёнными КТ и исследована их ФЛ. Показано, что после осаждения в AAО НК InP/ZnS, сохраняют свои флуоресцентные свойства, следовательно, можно говорить об успешном создании композитных люминофоров InP/ZnS@AAO. Обсуждаются цветовые характеристики изучаемых образцов. / This study deals with the investigation of optical characteristics of differently sized InP/ZnS colloidal quantum dots (QD-1, QD-2, QD-3) and composite nanostrucrures of anodic aluminum oxide with QDs by means of spectrophotometry and luminescence spectroscopy techniques. The literature review concerning electronic states in an ideal nanocrystal (NC), synthesis of InP-based QDs, use of NCs for creating nanocomposites and calculating color characteristics of emitters was carried out. The methods of sample preparation and measurements of optical absorption (OA) and photoluminescence (PL) spectra are described. Values of optical transition energies are determined according to the analysis of QD OA spectra. The bands with the lowest energy correspond to the first exciton absorption peak of the InP core. The other transitions can be attributed to the ZnS shell. The core size of the QD samples was evaluated using the blue shift. The temperature dependence of the first exciton absorption peak was investigated for the QD-1. PL spectra of QDs indicate that the emission bands are formed by exciton transitions and defects of the InP crystal lattice. A series of structures of nanoporous aluminum oxide, annealed at different temperatures, with deposited QDs were synthesized and their PL were studied. Fluorescent properties of the QDs are found to be retained after the deposition, therefore, InP/ZnS@AAO composite phosphors were successfully created. Сolor characteristics of the samples under study are discussed.