In this article we will show three recent examples of combined strategies aiming at merging top-down and bottom-up approach for nanofabrication at nanoscale level. The first example shows the fabrication of nanogaps performed by Focus Ion Beam technique that have been used to measure the conductivity of few gold nanoparticles aggregates deposited by Dip Pen lithography. The second example deals with the parallel replica of high resolution master generated by Electron Beam lithography by means of an innovative lithographic process based on DNA supramolecular nano-stamping. The latter example proposes the possibility to generate, through radiation exposure, direct patterning of hybrid sol gel material doped with fluorescent molecules. The outline of the fabrication approaches and their scientific and technical perspective are discussed.

A method for patterning biomolecules using electron beam (e-beam) lithography has been developed. First, a non-biofouling poly (ethylene glycol) terminated self-assembled monolayer (SAM) was deposited on a silicon oxide substrate. This SAM was then ablated by e-beam to create patterns aligned with the pre-existing features on the wafer. Aldehyde-terminated polyamidoamine (PAMAM) dendrimers were assembled in a layer-by-layer fashion in the ablated patterns to allow the covalent immobilization of oligonucleotide probes. The aminated oligonucleotides were attached using Schiff base chemistry followed by reductive amination. The functionality of the attached oligonucleotides was demonstrated by the hybridization of fluorescently labeled complementary target oligonucleotides. The hybridized target oligonucleotides could be stripped and the regenerated surface bound probe oligonucleotides could be rehybridized with complementary target oligonucleotide.

Biomaterials such as DNA are currently being explored as potential application in nanotechnology. DNA templates were immobilized on crystal-violet-treated mica by spin coating as a grid-like network. The DNA templates were then activated with PdCl2, followed by reduction with dimethylamine borane (DMAB) to form seeding nanoclusters on the DNA chain. Afterward the DNA chain with deposition of zero-valence Pd nanoclusters was grew in a Co electroless plating bath. SEM/EDS analysis revealed that Co nanoparticles could be assembled on the DNA template to form magnetic nanowires with a diameter of 25nm to 250nm by a conventional electroless plating. Vibrating Sample Magnetometer analysis indicated that Co-DNA nanowires showed a paramagnetic characteristic. Grid-like networks of DNA template were effectively preserved after Co electroless plating. These characteristics indicated that DNA is an ideal template for the production of magnetic nanowires, which could be useful in the development of high-density memory storage or magnetic field sensors.

Non-oxide ceramic materials like boron carbide and silicon carbide are technologically relevant as advanced high temperature materials, while boron nitride is a thermally robust low-k insulating material with electronic applications. Efficient routes to boron carbide, boron nitride, and silicon carbide ceramic nanostructures have been developed which employ molecular and polymeric precursors, including the boron carbide precursor 6, 6'-bis(decaboranyl)hexane, the boron nitride precursor polyborazylene, and a commercially available silicon carbide precursor allylhydridopolycarbosilane(AHPCS), in conjunction with colloidal silica and biological silica “diatom” templates. Layered submicron-sized ordered void structures with three-dimensional periodicity and tunable length scales were fabricated by the melt infiltration of the precursors into ordered colloidal silica bead templates. Pyrolytic ceramic conversion followed by dissolution of the silica beads by chemical treatment with aqueous HF or NaOH generated highly uniform ceramic structures with thicknesses up to 50μm and ordered voids ranging in diameter from 50-150 nm. Following on earlier work by Sandhage who generated polymer and oxide ceramic structures, vacuum filtration of the ceramic precursor solutions through bioclastic silica diatom frustule templates generated polymer coated replicas of their 3-D micro- and nanostructures. Subsequent pyrolysis and dissolution of the frustules in 48% HF yielded free-standing ceramic structures with fine features on length scales of 60-200 nm. This technique therefore provides a large scale route to nano- and micro structured non-oxide ceramic materials. Structural control of the end products was achieved by changing the concentration of the precursor solution, pore size and/or the frustule template. Characterization by XRD, DRIFT, SEM, TEM and possible uses of these uniform nano- and micro-structured ceramics will be discussed.

We present three-dimensional micro/nano-fabrication techniques to create new photonic and functional devices. We have demonstrated two-photon-induced photopolymerization for fabricating 3D micro/nano-structures [1, 2]. In this method, arbitrary three-dimensional polymer structures are fabricated by scanning tightly focused infrared femto-second laser in three dimensions. Recently, we extended this technique to fabricate functional micro devices including photonic band-gap crystals [3] and movable micro-springs. The shrinkage of polymer during polymerization is utilized to reduce the structure size beyond the diffraction limit of light [4]. A micro-lens array with 2500 lenses is used to produce a mass of structures in parallel. By using this micro-lens array system, we fabricated 800 micro-springs and micro-cubic structures by single laser scanning [5]. In this presentation, metalization of fabricated polymer structures will also be described. We coat metal on the surface of polymer by electroless metal plating, but not on the glass substrate [6]. Hydrophobic coating was pre-made on the glass substrates and polymer surface is modified with Sn2+-ions. With this method micro-coil array is metalized [7]. Micro-coil array exhibits negative refraction due to the excitation of magnetic field through coils. We would like to show our design of the structure [8]. In the end, we talk about our newly invented diffraction-free imaging with nano metal rod array [9].

A new approach to fabricate long length of gold nanorods by controlling the volume of growth solution will be reported. The shape evolutions ranging from fusiform nanoparticles to 1-D rods was observed. Increasing the addition of growth solution can control the length of nanorods. The length of rods can be extended to 2 £gm, and nanorods with aspect ratios of up to ~ 70 could be obtained. Moreover, X-ray absorption spectroscopy (XAS) is applied herein to elucidate the growth mechanism of gold nanorods. The gold ions were directly reduced to gold atoms by ascorbic acid during the reaction, and then gold atoms were deposited on the surface of gold seeds that were introduced into the reaction. Extended X-ray absorption fine structure (EXAFS) confirmed the growth of gold and the environment around Au atoms over the reaction. The XAS are expected to have wide applications in the growth of gold and other related materials.

Anodised aluminium oxide films have several applications in nanotechnology due to the ability to control the dimensions and ordering of the pores. Several techniques have been developed which allow for accurate control over the ordering of pore arrays. Examples of such techniques are the “Two-Step” method, and embossing with optical gratings or micro-machined Si templates. It will be demonstrated that it is possible to control the position of the pores using a nanoindenting device that has scratched the aluminium surface before anodising. The interpore distances accomplished via this technique were 200nm and 400nm by anodising in 0.3M (COOH)2 at 80V and 0.1M H3PO4 at 160V respectively. Hexagonal and square arrays were created by scratching the aluminium with a series of crosshatched lines.

A stressed epitaxial film can undergo surface instability. The stress field and the interface interaction have profound effects on the dynamics of surface evolution that leads to self-assembled quantum dots. In this paper, by using a nonlinear evolution equation, we investigate pattern evolution of self-assembled quantum dots under general biaxial stresses. It is found that the shape of quantum dots and their spatial ordering are strongly influenced by the relative magnitudes of the biaxial stresses. Linear perturbation analysis and nonlinear numerical simulations are conducted to elucidate the effect of stress anisotropy on the process of self-assembly that selects different patterns.

Recent studies in nanostructural characterization for on-chip interconnect applications using carbon nanofibers (CNFs) are presented. In this paper, we propose a novel technique, for the purpose of characterizing interfacial structures of vertically aligned CNFs for cross-sectional imaging with scanning transmission electron microscopy (STEM). In this technique, vertically aligned CNFs are selectively grown, by plasma-enhanced chemical vapor deposition (PECVD), on a substrate comprising a narrow strip (width ~100nm) fabricated by focused ion beam (FIB). Using high-resolution STEM, we show that CNFs with diameters ranging from 10 -100 nm exhibit very similar graphitic layer morphologies at the base contact interface.

Nanoindentations were created in the GaAs(100) surface to act as strain centers to bias the nucleation of self-assembled InAs quantum dots providing for patterned growth. Indents were generated using loads below 450 μN with a sharp cube corner indenter. Growth of InAs quantum dots on indent patterns is performed using molecular beam epitaxy (MBE). The effect of indent spacing and size on the patterned growth is investigated. The structural analysis of the quantum dots including spatial ordering, size, and shape are characterized by ex-situ atomic force microscopy (AFM). Results reveal that the indent patterns clearly bias nucleation with dot structures selectively growing on top of each indent. It is speculated that the biased nucleation is due to a combination of favorable surface strain and multi-atomic step formation at the indent sites, which leads to increased adatom diffusion on the patterned area.

We report the novel use of thermoplastic acrylic lacquer (automotive paint) in the hot embossing of nanoscale structures. Replicas of grating arrays have been produced in coatings of acrylic lacquer using a standard embossing process. The master dies for the experiments comprised grating arrays fabricated by electron beam lithography. Grating patterns with a pitch of 0.7-1.3 μm were configured to produce diffractive images over an area of ~25 × 25 mm. The embossing experiments used a replicated Ni shim as a die and were performed at 100-150 °C and 80 kN force. A temperature above the reflow range for the lacquer, T = 120-150° C, was required in order to achieve a uniform impression across the embossed area of ~80 × 80 mm. The diffractive grating patterns which were embossed into acrylic lacquer have shown optical effects suitable as a security feature including image switching and color movement.

Using solution micelles formed by a block copolymer template, a variety of highly ordered catalytically active transition metal nanoparticles, ranging from single metallic nanoparticles of Fe, Co, Ni and Au to bimetallic nanoparticles such as Ni/Fe with uniform size and periodicity, have been created. These nanoparticles are excellent catalyst systems for the synthesis of carbon nanotubes and silicon nanowires. High quality, small diameter carbon nanotubes and silicon nanowires with narrow size distribution have been successfully produced. Since this block copolymer is fully compatible with conventional top-down photolithography, spatially selective growth of carbon nanotubes and silicon nanowires on a surface or carbon nanotubes suspended across trenches have been achieved using standard semiconductor processing techniques. The ability of the block copolymer template to generate catalyst with adjustable size and composition on a variety of surfaces not only enhance the manufacturability of these 1D nanobuilding blocks but also facilitates studying the growth mechanism.

We describe that an elastomeric stamp of poly(dimethylsiloxane) (PDMS) can modify the surface energy of some surfaces when brought into conformal contact with the number of stamping. We focus on an increase of the hydrophobicity of the patterned surface due to diffusion of low molecular weight (LMW) silicone polymer chains. The transfer of PDMS to the surface during patterning is relevant to and calls for attention by those who are using this method in applications where control of the surface chemistry is of importance for the application.

We demonstrate here the use of Poly-L-lysine to mediate the mineralization of fractal titania structures.

An ion implantation-wafer bonding-layer splitting based 2-D nanostructure material fabrication method using polysilicon sacrificial layer for forming nanothick SOI materials without using post-thinning processes is presented in this paper. Polysilicon layer was initially deposited on the thermal oxidized surface of silicon wafer prior to the ion implantation step to achieve the hydrogen-rich buried layer which depth from the top surface is less than 100 nm in the as-implanted silicon wafer. Before this as-implanted wafer being bonded with a handle wafer, the polysilicon layer was removed by a wet etching method. A nanothick silicon layer was then successfully transferred onto a handle wafer after wafer bonding and layer splitting steps. The thickness of the final transferred silicon layer was 100 nm measured by transmission electron microscopy (TEM).

Planarization characteristics of ultra low diluted Ceria (CeO2) based slurry, especially a multi-layered Chemical Mechanical Polishing (CMP) process, have been studied. The multi-layer represents the polished film consists of more than two different materials, so that, more than two different materials are exposed to the polished surface. In this work, ultra low diluted ceria based slurry was introduced to minimize micro-dishing effect of the process such as a storage node contact and a bit line contact in 80nm feature sized DRAM device, which has multi-layer film surfaces. As a result, we can minimize micro dishing of silicon dioxide and polycrystalline silicon at memory cell area, and silicon dioxide dishing at peripheral area.

Biomaterials for development of resorbable, three-dimensional tissue scaffolds have been used in a modified thermal inkjet printing system to explore compatibility of materials, solvents and the printing system. The polymers included collagen (type I), sodium alginate, fibronectin, poly-lactic co-glycolic acid (PLGA), polyethylene glycol (PEG), and tetraglycol were tested. Single-walled carbon nanotubes were combined with the biopolymers to determine which systems in which they would blend well, and be able to print. Uncovering which biopolymers may be printed together offers insight into development of materials which most closely match the properties of biological tissue.

We demonstrate that hexagonally packed single-crystalline Ge rings can be grown around the contact region between self-assembled SiO2 spheres and 1.2-nm-thick chemical SiO2 on Si. When the oxide-covered Si substrate is pulled from a colloidal suspension of SiO2 spheres, the SiO2 spheres self-assemble into a hexagonally packed monolayer on the substrate. These SiO2 spheres provide a surface diffusion path to guide the Ge adspecies to reach the substrate. We have previously determined that the Ge adspecies readily desorb from the bulk SiO2 surface with a desorption activation energy of 42±3 kJ/mol. This low desorption activation energy gives rise to a low surface diffusion barrier, which in turn leads to a high diffusion length on the order of several micrometers, exceeding the dimension of the SiO2 spheres. With a flux of Ge impinging at 45° from the surface normal, the Ge beam cannot directly impinge on the underlying substrate through the openings between SiO2 spheres. The Ge adspecies diffuse around the SiO2 spheres and "touchdown"[Li et al., APL, 85(11), 1928 (2004)] through the chemical SiO2, forming epitaxial ring structures. The touchdown process anchors nanoscale Ge seed pads to the underlying Si substrate. The ring formation uniquely takes advantage of the SiO2 sphere self-assembly; the weak interaction between Ge adspecies and SiO2; and the touchdown where Ge densely nucleates on Si surface through the 1.2-nm-thick chemical oxide.

Even though viability for printed bacteria has been demonstrated, the effect of thermal ink-jet printing on cellular ultrastructures is unknown. Retention of viability is useful when colony growth is desired. However, when bacteria are isolated from a human infection they often exhibit characteristics that can be lost when grown in standard laboratory cultures. Ideally, individual bacteria from an infection could be printed and studied without extensive culturing or processing.

We have investigated the gram-positive organism Staphylococcus aureus and the extracellular polymeric ultrastructure that encapsulates the bacterial cell. The capsule is composed of cell-wall associated polysaccharides. Our goal was to use ink-jet printing to spatially control the placement of S. aureus, without affecting the extracellular ultrastructure. Observation by scanning electron microscopy comparing the integrity and uniformity of encapsulated S. aureus before and after thermal ink-jet printing suggests that the capsule is disrupted, possibly completely removed, during printing.

Composite nanofibers including ferritin nanoparticles or multiwalled carbon nanotubes (MWCNTs) were fabricated to enhance the physical properties of the nanofibers, such as the elastic modulus and electrical conductivity. The ferritin was homogeneously incorporated in the polymeric nanofibers, but excess carbon nanotubes (CNTs) added to the polymer solution resulted in the fabrication of composite nanofibers with rough surfaces. PVA/ferritin/CNT composite nanofibers were fabricated that had smooth surfaces, and had a good dispersion of ferritin and CNTs. These composite nanofibers are applicable to artificial muscles requiring enhanced physical properties.