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Directed self-assembly (DSA) of the domain structure in block copolymer (BCP) thin films is a promising approach for sub-10-nm surface patterning. DSA requires the control of interfacial properties on both interfaces of a BCP film to induce the formation of domains that traverse the entire film with a perpendicular orientation. Here we show a methodology to control the interfacial properties of BCP films that uses a polymer topcoat deposited by initiated chemical vapour deposition (iCVD). The iCVD topcoat forms a crosslinked network that grafts to and immobilizes BCP chains to create an interface that is equally attractive to both blocks of the underlying copolymer. The topcoat, in conjunction with a chemically patterned substrate, directs the assembly of the grating structures in BCP films with a half-pitch dimension of 9.3 nm. As the iCVD topcoat can be as thin as 7 nm, it is amenable to pattern transfer without removal. The ease of vapour-phase deposition, applicability to high-resolution BCP systems and integration with pattern-transfer schemes are attractive properties of iCVD topcoats for industrial applications. A thin topcoat that grafts directly to block copolymer films does not need to be removed prior to further fabrication steps.

Over the last few years, significant improvements in sources, columns, detectors, control software, and accessories have enabled a wealth of new focused ion beam applications. In addition, modeling has provided many insights into ion-sample interactions and the resultant effects on the sample. With the knowledge gained, the community has found new ion-beam induced chemistries and ion-beam sources, allowing extending nanostructure fabrication and material deposition to smaller dimensions and better control for direct write and patterning. Insignificant proximity effects in resist-based ion beam lithography, combined with the availability of sub-nm ion spot sizes, opens the way to sub-10 nm structures and dense patterns. Additionally, direct-write ion beam nanomachining can process multilevel structures with arbitrary depths in one single process step, with all the information included in a single standard design file, thus enabling fabrication applications not achievable with any other technique. © 2014 Materials Research Society.

Hard X-ray phase zone plates are focusing optics used for X-ray microscopes at synchrotron radiation facilities. The resolution is determined by the outer-most zone width (OZW) and modern lithographic techniques are capable of patterning OZW less than 100 nm. Efficiency of a phase zone plate will peak when the zones have a thickness that provides a ?-phase shift to the X-rays. Thus, a hard X-ray zone plate with ideal efficiency and sub-100-nm resolution requires fabricating high-aspect-ratio, dense-packed structures in materials suitable for exposure to synchrotron radiation. The fabrication method implemented involves an electroforming mold process where a top resist layer is lithographically patterned and used for pattern transfer into a bottom layer which acts as the electroform mold. The resulting mold is filled with Au by electroplating, and afterwards the mold is not removed but remains in place for mechanical support. Ultrananocrystalline diamond (UNCD) was used as the mold layer. UNCD is deposited by hot-filament chemical vapor deposition with well-controlled stress and thickness up to 2 μm. The top resist layer is hydrogen silsesquioxane, which is a high-contrast electron beam lithography resist and resistant to the oxygen reactive ion etching required for UNCD pattern transfer. Using this fabrication method, we successfully produced zone plates with OZW down to 80 nm and an aspect ratio up to 25 for a thickness of 2 μm. The efficiency of several fabricated zone plates were measured, demonstrating their functionality.

Nonlinear optical responses of materials play a vital role for the development of active nanophotonic and plasmonic devices. Optical nonlinearity induced by intense optical excitation of mobile electrons in metallic nanostructures can provide large-amplitude, dynamic tuning of their electromagnetic response, which is potentially useful for all-optical processing of information and dynamic beam control. Here we report on the sub-picosecond optical nonlinearity of indium tin oxide nanorod arrays (ITO-NRAs) following intraband, on-plasmon-resonance optical pumping, which enables modulation of the full-visible spectrum with large absolute change of transmission, favourable spectral tunability and beam-steering capability. Furthermore, we observe a transient response in the microsecond regime associated with slow lattice cooling, which arises from the large aspect-ratio and low thermal conductivity of ITO-NRAs. Our results demonstrate that all-optical control of light can be achieved by using heavily doped wide-bandgap semiconductors in their transparent regime with speed faster than that of noble metals., Optical nonlinearity in metallic nanostructures has been exploited for all-optical signal switching. Here, Guo et al. report on the optical nonlinearity of indium tin oxide nanorod arrays in the dielectric range induced by pumping in the metallic range, enabling modulation of the full-visible spectrum.

Researchers demonstrate coherent X-ray surface scattering imaging in a grazing-incidence geometry that takes advantage of enhanced X-ray surface scattering and interference near total external reflection. Surface patterns are reconstructed in three dimensions with nanometre resolution. The approach has applications in the analysis of buried nano-electronic and nanophotonic structures.

A sensitive and selective field-effect transistor (FET) biosensor is demonstrated using vertically-oriented graphene (VG) sheets labeled with gold nanoparticle (NP)-antibody conjugates. VG sheets are directly grown on the sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method and function as the sensing channel. The protein detection is accomplished through measuring changes in the electrical signal from the FET sensor upon the antibody-antigen binding. The novel biosensor with unique graphene morphology shows high sensitivity (down to ~2 ng/ml or 13 pM) and selectivity towards specific proteins. The PECVD growth of VG presents a one-step and reliable approach to prepare graphene-based electronic biosensors.

Electron-beam-induced deposition (EBID) using gas-phase precursor molecules is an extensively studied fabrication technique. Liquid-phase metal deposition has recently been shown to achieve higher purity levels than traditional gas-phase deposition [1]. The goal of this investigation was to characterize liquid-phase silver deposition for further studies in photonics. A Scanning Electron Microscope (SEM) (FEI Nova 600 NanoLab Dual Beam) was used to deposit silver on polyimide membranes from aqueous AgNO3 solution by accelerating electrons into the solution for silver ion reduction. Atomic Force Microscopy (AFM) and SEM were subsequently used to characterize the size dependence to electron dosage. We observed granular silver deposits with sub-75 nm particle size and 200-250 nm total aggregate diameters. The CASINO (monte CArlo SImulation of electroN trajectory in sOlids) program was used to model electron trajectory in the solution to relate the size to the electron spread.

Two dimensional photonic crystal (PhC) microcavity structures were fabricated using epitaxial ferroelectric thin film as the optical media and their resonant optical properties were measured. The PhC structures are utilized in order to achieve strong light localization to enhance the interaction between the incident light and the nonlinear optical barium titanate (BTO). Fluorescence measurements were used to assess the resonant properties. Two types of resonant structures were investigated consisting of either dopant or vacancy PhC arrays. The nano patterning on BTO thin films was achieved using dual beam focused ion beam (FIB). For the dopant type PhC microcavity structure, a larger air hole is generated in every 5 x 5 unit cells forming a super cell. The spatial profiles of PhC microcavity structures are characterized by laser scanning confocal microscopy. Structures with a feature size approaching the optical diffraction limit are clearly resolved. Fluorescence measurements on PhCs coated with a fluorescent dye were carried out to determine the relationship between the degree of light localization and the photonic band structure. Enhanced fluorescence at wavelengths 550-600 nm is observed in the dye covered PhCs with lattice period a =200 nm and a =400 nm. The large fluorescence enhancement results from the presence of PhC stop bands that increase the emission extraction efficiency due to the strong light confinement. Since the only allowed propagation direction for the scattered fluorescence light is out-of-plane, this enhances the vertically fluorescent extraction efficiency. These BTO optical microcavity structures can potentially serve as active nano-photonic components in bio-sensors and integrated photonic circuits.

In this work, we investigate the feasibility of using a surface-tethered heptapeptide sequence as the basis for a ferroelectric-actuated component in a nanofluidic device. The fluorescently-labeled peptide sequence, (CISLLHSTC) is shown by fluorescence microscopy to selectively coat the PZT patterned channel floors. The peptide binding strength to PZT is determined over a range of flow rates in the patterned channel by imaging the fluorescence intensity of the coated channel and monitoring the output spectroscopically. The peptide is found to be stripped from the PZT at flow rates exceeding 5mL/h. Initial results demonstrating the possibility of covalently integrating the short peptide sequence to larger biological components such as antibodies are also presented.

The integration of biomolecules with inorganic materials to create functional composites represents a critical step in the development of next-generation biosensors, micro/nanofluidic devices, and biochips that require a combination of abiotic (inorganics) and biotic (proteins, DNA, antibodies) components. Toward this end, we have previously applied combinatorial phage display techniques to identify a constrained heptapeptide sequence (CISLLHSTC) that selectively binds to a perovskite ferroelectric (MOCVD-deposited lead zirconium titanate, PZT). In this work, we examine the binding of this heptapeptide sequence, prepared by solid phase peptide synthesis to sol-gel PZT. In particular, the surface roughness has been examined and the long-term stability of the PZT films in biological buffered aqueous solutions by atomic force microscopy, X-ray diffraction and P-E hysteresis loop. In addition, the selectivity of the peptide binding to PZT has been determined by immunofluorescence microscopy and the nature of peptide binding to the PZT surface is probed by X-ray photoemission spectroscopy.

Electron beam lithography still represents the most effective way to pattern materials at the nanoscale, especially in the case of structures, which are not indefinitely repeating a simple motif. The success of e-beam lithography depends on the availability of suitable resists. There is a substantial variety of resist materials, from PMMA to calixarenes, to choose from to achieve high resolution in electron-beam lithography. However, these materials suffer from the limitation of poor sensitivity and poor contrast.In both direct-write and projection e-beam systems the maximum beam current for a given resolution is limited by space-charge effects. In order to make the most efficient use of the available current, the resist must be as sensitive as possible. This leads, naturally, to the use of chemically amplified (CA) systems. Unfortunately, in the quest for ever smaller feature sizes and higher throughputs, even chemically amplified materials are limited: ultimately, sensitivity and resolution are not independent. Current resists already operate in the regime of < 1 electron/nm2. In this situation detailed models are the only way to understand material performance and limits.Resist requirements, including sensitivity, etch selectivity, environmental stability, outgassing, and line-edge roughness as they pertain to, high-voltage (100 kV) direct write and projection electron-beam exposure systems are described. Experimental results obtained on CA resists in the SCALPEL® exposure system are presented and the fundamental sensitivity limits of CA and conventional materials in terms of shot-noise and resolution limits in terms of electron-beam solid interactions are discussed.

This paper will discuss aspects of resist properties required for nanolithography using high-energy electrons. A comprehensive image formation model is presented for positive and negative chemically amplified resists where most aspects have been considered (from exposure through development) for e-beam nanolithography (EPL, DWL). A series of optimization studies are performed using the modulation of soluble site density after PEB as a metric to characterize resist imaging performance. Base loading, blocking fraction and acid diffusion properties are investigated. Slower acid diffusion near regions with deprotected sites dominates during PEB and contributes to a sharp image modulation. Electron beam exposed nanostructures exhibit spatial fluctuations of soluble sites in the material left after development, which may alter etch resistance and pattern collapse. Soluble site fluctuations arise from the low statistics involved in the image formation and are significant contributors to the sidewall roughness.

This article reviews technology issues in scaling conventional planar transistors to a physical gate length of 30nm that are expected to produce an effective channel length of 10 nm. Gate fabrication features direct write e-beam lithography to form a ring structure capable of exploring the practical limits of gate processing while requiring only a single level of lithography. Other processing elements include ultra-thin gate dielectric formation (∼ 0.6nm); highly selective transformer coupled plasma (TCP) etching; and low energy ion implantation. DC electrical results obtained for high performance n-MOS and p-MOS type nanotransistors made using this process are discussed as are simulations of sub-threshold currents for n-MOS transistors with physical gate lengths down to 26nm

The study of photoelectron effects in X-ray Lithography motivates the need for modeling codes to simulate these effects to have an estimate of the influence of x-ray generated photoelectrons in the exposure of resists. We have performed a series of Monte Carlo simulations to study the spatial distribution of photoelectrons in a resist, PMMA, and parametrized this distribution with a set of energy-dependent gaussians for monochromatic X-rays within an energy range of 0.5 KeV to 2.5 KeV. We discuss the effects of the the redistribution of the photoelectron kinetic energy as a function of the electrons generated by the x-ray absorption in various atomic species.