The molecular/crystal orientation and morphology of active molecular structures is a key determinant for the function of nanoscaled organic devices. In π-conjugated systems, both charge transport and optical properties will strongly depend on the molecular orientation due to the highly anisotropic charge carrier mobility in these organic crystals and the anisotropic absorption and luminescence behavior of the molecules. Although the importance of organic on inorganic interface formation and thin film growth is widely acknowledged, little is known regarding the growth kinetics. A better understanding of the processes driving molecular self-assembly is necessary if the self-assembly process is to be controlled. Moreover, it is interesting as the anisotropy of the molecular building blocks presents a fundamental difference from what is known from inorganic growth. Here we show that either sticking or diffusion anisotropy can control the growth depending on preparation conditions. This is illustrated by an investigation into the growth of sexiphenyl (6P) on the anisotropic TiO2(110)-(1×1) surface for temperatures between 80K and 400K using in-situ UHV photoemission, x-ray absorption spectroscopy, synchrotron x-ray diffraction and ex-situ atomic force microscopy. For 6P adsorption even at 80K we found that the molecules orient parallel to the TiO2 oxygen rows and form small crystallites. At 300K this molecular orientation is retained and large micrometer sized 6P(203) oriented needles running perpendicular to oxygen substrate rows are formed. In contrast, for growth at elevated temperatures the 6P molecular axis is near perpendicular to the surface and large islands elongated parallel to the substrate rows are formed. These differences in crystallite orientation and morphology can be explained by the domination of the growth kinetics by either sticking or diffusion anisotropy depending on growth temperature.

We have fabricated three-dimensional (3D) colloidal crystals containing a two-dimensional (2D) defect as the middle layer by the Langmuir-Blodgett (LB) technique. Either a homogeneous sheet made of hundreds layers of behenic acid or a single monolayer of silica colloidal particles of various sizes was inserted between two opal films of silica spheres. The presence of the extrinsic defect led to an impurity mode within the photonic stop band, which was observed as a pass band in the near-infrared (NIR) spectra. The position of this defect mode was found to vary periodically with the value of the ratio of the thickness of the defect layer to the diameter of the colloids of the upper and lower opals.

Titanium dioxide macro-cellular monolith-type materials have been obtained with emphases toward controlling porosity at the meso- and macroscopic length scales, leading thus to hierarchically organized porous architectures. First, at the microscopic length scale, either monophasic Anatase, biphasic Anatase-Rutile or monophasic Rutile allotropic forms are generated by varying the applied thermal treatment. At the meso- and/or nanoscopic length scales either lyotropic templates or latex colloids have been used to promote meso- or super-mesoporosity. Particularly, a Pluronic copolymer P-123 combined with cationic surfactant (TTAB) induces vermicular-like mesoporosity associated with a specific surface area around 450 m2·g-1. At the macroscopic length scale a non-static air-liquid foam strategy allows a strong control over the open-cell morphologies.

Using readily available materials and equipment we are able to sculpture aluminium wires into cylindrical, bi-directional templates for the synthesis and contacting of nanowires as field-effect transistors. The nanowire template is made by partial anodization of the wire perpendicular to its axis as an isolating layer for a gate electrode, vapour deposition of a metal on this layer as a gate, cutting the wire perpendicular to its axis, and finally anodizing the newly exposed area parallel to the wire axis as a template for nanowires. This results in a nanowire template surrounded by a gate electrode that is isolated from the template by the first anodisation layer.

The utility of this structure is demonstrated by a ZnO nanowire field-effect transistor. The ZnO was made by electrodeposition of Zn nanowires in the interior nanoporous template during which an anodic pulse was applied to form a layer of ZnO in the middle of the zinc nanowires. The IV and transfer plots indicate that the ZnO is p-type in depletion mode.

This 3-D transistor is unique in that it can be totally fabricated in a beaker without the need for costly clean room and lithography facilities. The ease and low cost of this new approach to nanodevices will have the effect of liberating nanoscience for scientists of moderate means. As a result this will open nanoscience to new ideas and more inputs.

A mathematical model describing how a cell membrane with diffusive mobile receptors wraps around a ligand coated cylindrical or spherical particle has been recently developed to model particle size effects in receptor mediated endocytosis. The model predicted an optimal particle size for the smallest wrapping time, as well as a minimum and a maximum particle size for successful wrapping. The results showed that particles in the size range of tens to hundreds of nanometers can enter cells even in the absence of clathrin or caveolin coats. Here we report some further progresses on modeling a spontaneous membrane curvature induced by clathrin or caveolin coats at the inner membrane leaflet as well as simultaneous entry of many particles into cells. It is found that a spontaneous membrane curvature narrows the particle size range for successful wrapping and there exists an optimal particle density for maximum particle adsorptivity.

Synthetic opals serve as templates for the most promising three-dimensional photonic crystals, so-called inverted opals. The time consuming growth of artificial opals by self-assembly of monodisperse sub-micron spheres made of silica or organic materials resulting in fcc and hcp colloidal crystals usually yields in limited crystal qualities. The large scale fabrication and thus their application in photonics suffer from the reproducible growth of defect-free extended bulk crystals. In this paper we propose a sonic wave supported fast colloidal crystal growth in a centrifugal field. White noise acoustic irradiation is thought to realize an artificial temperature allowing particle diffusion during crystal growth.

Quantum dots (QDs) have been shown to improve the efficiency and optical properties of opto- electronic devices compared to two dimensional quantum wells in the active region. The formation of self-assembled GaN nanostructures on aluminum nitride (AlN) grown on sapphire substrates by Metal Organic Chemical Vapor deposition (MOCVD) was explored. This paper reports on the effect of in-situ activation in nitrogen atmosphere on MOCVD grown GaN nanostructures. The effect of introducing manganese in these nanostructures was also studied. Optically active nanostructures were successfully obtained. A blue shift is observed in the photoluminescence data with a decrease in nanostructure size.

Carbon nanotubes (CNT) have been studied intensively for its unique electrical and mechanic properties and numerous applications. However, electronical integration of carbon nanotubes with silicon to form an electronically functional entity or device, though highly desirable, has remained a great challenge. Whereas vertical aligned bundles of nanotubes have been grown directly on silicon, the integration is mechanical, rather than electronical, in nature. In the present work, we report on Controlled growth of vertical and highly-ordered array of ’carbon nanotube silicon’ (CNS) heterojunction diodes of uniform diameter, length, and alignment. The as grown CNS heterojunction structure is not only electronically functional but also strongly rectifying with an on off ratio as high as five orders of magnitude in current voltage characteristics measured at room temperature. The controlled direct growth of the CNS hetero junction array of such high uniformity is enabled by the formation of a highly ordered nanopore array alumina matrix directly on the silicon, following a precisely controlled anodization of an aluminum thin film evaporated on silicon. Iterations of development and optimization of the anodization process conditions and real time monitoring and control of the anodization process were required for the formation and adhesion of the alumina growth matrix directly on silicon. Under carefully controlled and optimized conditions developed in this work, we are able to obtain an abrupt heterointerface between a terminal end of the carbon nanotube and the silicon substrate, without an intermediate barrier layer, as required for an electronically functional CNS hetero junction. The growth process is applicable to silicon doped in either type, enabling access to another critical parameter of the electronic function.

The hierarchical design of well-defined and highly oriented two- and three-dimensional arrays of conventional semiconductor nanomaterials and their large scale manufacturing at low cost remain a crucial challenge to unfold the very promising future of nanodevices. In addition to economical manufacturing of nanostructured semiconductors, better fundamental knowledge of their electronic structure, physical, interfacial and structural properties and stability, is required to fully exploit their fascinating potentials. To combine such essential requirements, the predictive creation of structurally well-defined and well-ordered functional and multi-functional materials is essential. As an attempt to achieve such ambitious goals, a novel strategy to thin film metal oxide semiconductor nanotechnology processing has been developed and investigated. A thermodynamic growth control concept based on the chemical and electrostatic minimization of the surface energy as well as a thin film growth technique have been developed. Such original approach allows the generation of nanomaterials with novel and functional morphologies. Advanced metal oxide nanostructures consisting of oriented multi-dimensional arrays featuring building blocks of controlled morphologies, sizes, aspect ratios and orientations at nano-, meso-, and microscale are genuinely fabricated directly onto various substrates of large physical areas without template, surfactant, undercoating or applied field from the hydrolysis-condensation of aqueous metal salts solutions at mild temperatures (below 100°C). A survey of the innovative advances in the fabrication of highly oriented and functional nanostructure arrays of transition and post-transition metal oxides are presented as well as one-dimensional confinement effects in purpose-built bundled iron oxide quantum rods.

Amorphous niobium oxide (Nb2O5) nano-tubes were fabricated inside anodic alumina templates using atomic layer deposition (ALD). The nanoporous templates were in-house fabricated anodic alumina membranes having an inter-pore distance of about 100 nm with pores lengths of 2 µm. The pores were parallel and well ordered in a hexagonal pattern. Atomic layer deposition was performed using gas pulses of niobium iodide (NbI5) and oxygen separated by purging pulses of argon. By employing long gas pulses (30 s) it was possible to get coherent and amorphous Nb2O5 films conformally covering the pore-walls of the alumina template. The outer diameter of the nano-tubes was tailored between 40 and 80 nm by using alumina templates with different pore sizes. By using template membranes with pores not opened in the bottom, nano-tubes with one side closed could be fabricated. Free-standing, and still parallel, nano-tubes could be obtained by selectively etching away the alumina template using phosphoric acid. Using the above mentioned procedure it was possible to fabricate unsurpassed parallel niobium oxide nano-tubes of equal length, diameter and wall-thickness, ordered in a perfect hexagonal pattern. The samples were analysed using high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), electron diffraction and x-ray fluorescence spectroscopy (XRFS).

Nanoparticles thin films have wide range of applications such as nanoelectronics, magnetic storage devices, SERS substrate fabrication, optical grating and antireflective coating. Present work describes a method to prepare large area nanoparticles thin film of the order of few square centimeters. Thin film deposition has been done successfully on a wide range of conducting as well as non conducting substrates such as carbon-coated copper grid, silicon, m-plane of alumina, glass and (100) plane of NaCl single crystal. SEM, TEM and AFM studies have been done for microstructural characterization of the thin films. A basic mechanism has been proposed towards the understanding of the deposition process.

Highly crystalline zinc oxide (ZnO) nanomaterials are synthesized using a seeded growth sol-gel method. In order to control the morphology and the organization of the ZnO nanomaterials, a double hydrophilic block copolymer has been introduced during the seeded growth synthesis: the Polyacrylic acid-Polyacrylamide (PAA-PAM). Depending on the amount of PAA-PAM copolymers, different morphologies were obtained, such as ZnO nanostructured spheres or flat hexagonal crystals. Thus, systematic studies have been done to investigate the influence of the copolymer addition on ZnO nanomaterial morphologies and explain the mechanisms of the morphological modifications.

Directed assembly of nanoparticles and single wall carbon nanotubes (SWNTs) using electrostatically addressable templates has been demonstrated. Nanoparticles down to 50 nm are assembled on the Au micro and nanowires of the templates in a DC and AC electric fields. The nanoparticles can be assembled in monolayers and thicker layers. Single wall carbon nanotubes (SWNTs) are also assembled without alignment on Au wires using the nanotemplate. As the size of the template wires is reduced to nanoscale dimensions, an AC electric field proves to be more effective for nanoparticle assembly than a DC electric field.

Combining inorganic and organic components to create functional materials has been an active area of research in recent years. Inorganic components possess useful electric, photonic, or magnetic properties while organic components can self-assemble into a variety of morphologies on the nanoscale. We describe a novel approach for arraying nanoparticles using a modified diblock copolymer scaffold. Thin (30 nm) films of poly(styrene-block-methylmethacrylate) (PS-b-PMMA) copolymer were used as a substrate. Upon annealing, PS-b-PMMA forms lying-down cylinders of PMMA in a matrix of PS. These thin films were modified by exposure to ultraviolet light in vacuum which photochemically thinned the PMMA, creating a more highly corrugated surface. We find that colloidal superparamagnetic FePt nanodots and semiconducting CdSe nanodots deposited on this surface show a strong preference for the photochemically modified phase. This hierarchical self-assembly method may prove useful for many nanomaterials-based applications.

Layer-by-layer films incorporating single-wall carbon nanotubes (SWNTs) with anionic or cationic coatings have been prepared. The process of self-assembly was monitored using the quartz microbalance technique, while the morphology of the resulting thin layers was studied with atomic force microscopy. A variety of different architectures have been built up. The dc conductivities of the thin films, in-plane and out-of-plane, were measured at room temperature and contrasted with reference architectures. The results show clearly that the incorporation of SWNTs into the multilayers resulted in electrically conductive thin films.

Arrays of multi-walled carbon nanotunbe (CNT) bundles were fabricated on silicon [100] substrate with iron-nitrate sol-gel catalyst patterned via standard photolithographic techniques. Nanotube bundles with diameters ranging from 400µm to 15µm were grown in a chemical vapor deposition reactor and electrically characterized using a scanning-anode probe apparatus. Results showed a relatively low number of graphitic layers in individual nanotubes and a definite increase in field emission performance with decreasing bundle diameter. A 400µm wide matt of CNTs yielded a turn-on field of 6.7 V/µm and field enhancement of 602 while 15µm bundles performed significantly better with turn-on fields of 1.6 V/µm and field enhancement factors of 2425. The overall trend strongly suggests that the field emission character of CNT based aggregate structures such as those presented here is proportional to their aspect ratio.

Controlled defects were created on DNA linked 2-D colloidal photonic crystals using a Nd:YAG pulsed laser. The 2-D photonic crystals were self-assembled using 1.8 μm polystyrene (PS) microspheres on functionalized glass substrates. To synthesize the hexagonal close packed crystalline samples, both substrate and particles attached single-strand DNA, sequence A on the substrate and sequence B on the particles. The DNA was hybridized using the DNA linker with complementary single-strand A’B’ that anchored the particles to the substrate during self-assembly. The 532 nm second harmonic wavelength beam of the pulsed Nd:YAG laser (1064 nm) with a pulse width of 10 ns was used for the removal of individual colloidal particles from the self assembled photonic crystals. In the present tests, the diameter of the laser beam was optically reduced from 7 mm to about 1.8 μm. Controlled line defects and geometrical shapes (e.g., hexagonal and triangle) were created in the 2D arrays in an aqueous medium.

We here demonstrate the use of semiconductor chalcogenide nanocrystals as single-source precursors for the one-step formation of flexible functional films. By taking advantage of the surface chemistry of these “zero-dimensional” building blocks we obtain close-packed three-dimensional arrays of nanocrystals interconnected by oxide sheaths. The films are obtained by exposing oxidation-resistant nanocrystals to an air plasma treatment. This treatment does not significantly influence the photoluminescence efficiency of the individual nanocrystal building blocks but confers them resilience to bending as well as resistance to acidic environments, hot solvents, annealing, and UV irradiation.

The epitaxial growth of InAs nanowires on an InAs (111) substrate in a sealed quartz tube is described. The method is quite simple and fast, and uses only a bare InAs substrate and a gold colloid coated InAs (111) substrate. High quality InAs nanowires can be produced by this technique.

Carbon coated nanoparticles were synthesized by laser-assisted (ArF excimer laser, λ = 193 nm) chemical vapor deposition (LCVD). The particles were formed in the gas-phase by photolytic dissociation of cobaltocene in argon and the particles were deposited onto a silicon substrate. The particles were deposited at two different laser fluencies, 70 and 300 mJ/cm2.

Single crystalline spherical cobalt particles with a well-defined carbon shell were observed by transmission electron microscopy (TEM) for the highest fluence, 300 mJ/cm2. The metallic nucleus phase were identified as either β-Co or Co3O4. Polycrystalline particles were deposited at 70 mJ/cm2, these particles contained α-Co, β-Co, CoO and Co3O4. The particles deposited at 300 mJ/cm2 were log-normally distributed and the total diameter had a mean geometric size of 25 nm while the nuclei had a mean diameter of 10 nm. X-ray photoelectron spectroscopy (XPS) measurements showed that the particles had a carbon content roughly ten times the amount of cobalt. Sputtering showed that both cobalt oxide and metallic cobalt was present. HRTEM micrographs of the particles revealed that only one phase was present in the whole nucleus, proving the nuclei were either oxide or metallic. Raman spectroscopy showed that that the carbon shell contained mostly amorphous carbon. Small domains of carbon of more graphitic character was embedded in the amorphous carbon shell in the 300 mJ/cm2 sample.