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Chemiresistive sensors fabricated by oleylamine-functionalized palladium nanoparticles (OLA-PdNP) have been studied in hydrogen sensing, but not so much in organic vapor sensing. Like the extensively studied gold nanoparticles-based gas sensors, palladium nanoparticles also give the ease of surface modification and large surface-area-to-volume ratio. In this study, we demonstrate an OLA-PdNP chemiresistor array with robust sensor responses (1-15% of ΔR/R₀) and accurate discrimination of six organic vapors at a concentration of p/p₀ = 0.2, using principal component analysis (PCA). Each microfabricated 36 mm² chip has 36 individual sensors. By incorporating multiple sensors on one chip, the sensor response gives a distinguishable pattern for each analyte. From this study, an electronic chemical spectrometer can be further developed by incorporating many types of ligands on palladium metal core to enhance sensor accuracy and precision.

Plasmonic nanostructures with electrical connections have potential applications as new electro-optic devices due to their strong light–matter interactions. Plasmonic dimers with nanogaps between adjacent nanostructures are especially good at enhancing local electromagnetic (EM) fields at resonance for improved performance. In this study, we use optical extinction measurements and high-resolution electron microscopy imaging to investigate the thermal stability of electrically interconnected plasmonic dimers and their optical and morphological properties. Experimental measurements and finite difference time domain (FDTD) simulations are combined to characterize temperature effects on the plasmonic properties of large arrays of Au nanostructures on glass substrates. Experiments show continuous blue shifts of extinction peaks for heating up to 210°C. Microscopy measurements reveal these peak shifts are due to morphological changes that shrink nanorods and increase nanogap distances. Simulations of the nanostructures before and after heating find good agreement with experiments. Results show that plasmonic properties are maintained after thermal processing, but peak shifts need to be considered for device design.

Modern integrated circuits have active components on the order of nanometers. However, optical devices are often limited by diffraction effects with dimensions measured in wavelengths. Nanoscale photodetectors capable of converting light into electrical signals are necessary for the miniaturization of optoelectronic applications. Strong coupling of light and free electrons in plasmonic nanostructures overcomes these limitations by confining light into sub-wavelength volumes with intense local electric fields. Localized electric fields are intensified at nanorod ends and in nanogap regions between nanostructures. Hot carriers generated within these high-field regions from nonradiative decay of surface plasmons can be injected into the conduction band of adjacent semiconductors, enabling sub-bandgap photodetection. The optical properties of these plasmonic photodetectors can be tuned by modifying antenna materials and geometric parameters like size, thickness, and shape. Electrical interconnects provide connectivity to convert light into electrical signals. In this work, interconnected nanogap antennas fabricated with 35 nm gaps are encapsulated with ALD-deposited ${\mathrm{\text{TiO}}}_2$, enabling photodetection via Schottky barrier junctions. Photodetectors with high responsivity (12$\mu$A/mW) are presented for wavelengths below the bandgap of ${\mathrm{\text{TiO}}}_2$ (3.2eV). These plasmonic nanogap antennas are sub-wavelength, tunable photodetectors with sub-bandgap responsivity for a broad spectral range.

We discuss the problem of assembling complex physical systems that are structured from the nanoscale up through the macroscale, and argue that embryological morphogenesis provides a good model of how this can be accomplished. Morphogenesis (whether natural or artificial) is an example of embodied computation, which exploits physical processes for computational ends, or performs computations for their physical effects. Examples of embodied computation in natural morphogenesis can be found at many levels, from allosteric proteins, which perform simple embodied computations, up through cells, which act to create tissues with specific patterns, compositions, and forms. We outline a notation for describing morphogenetic programs and illustrate its use with two examples: simple diffusion and the assembly of a simple spine with attachment points for legs. While much research remains to be done — at the simulation level before we attempt physical implementations — our results to date show how we may implement the fundamental processes of morphogenesis as a practical application of embodied computation at the nano- and microscale.

An atom lens generated by a near-resonant light standing wave can be used to produce nanometer-scale structures. Our calculations are based on a Monte Carlo scheme and the trajectory tracing method. The influences of optical potential and source imperfection such as velocity spread and beam spread on the shape of chromium feature are analyzed using this approach. Results have shown that the focus depth for real source is longer than that for perfect source. Feature separation can be reduced by changing the detuning of the standing wave laser field from blue to red halfway through the deposition time.

A novel nanofabrication method that combines both "bottom-up" (template-assisted peptide self-assembling) and "top-down" (replica molding) techniques is introduced. A designer peptide, GAV-9 (NH₂-VGGAVVAGV-CONH₂), can epitaxially self-assemble into nanofilaments on the surface of mica, which is further used as the diversified masters for the application of replica molding. With in situ atomic force microscopy monitoring, several typical masters are fabricated by peptide self-assembling on the surface of mica. These masters can be easily molded into hard poly(dimethylsiloxane) surfaces, and then further replica-molded into polyurethane surfaces. The polymeric surfaces with regular 1D and 2D patterns on the nanometer scale are expected to have new applications in nanostructure's fabrication.

Direct laser writing (DLW) has become a routine tool for fabricating microstructures through two photon polymerization. Due to the diffraction limit, the resolution is usually larger than a quarter of a wavelength. In this article, by using stimulated emission depletion (STED) inspired lithography, we fabricate nanodot of 81 nm in diameter and nanoline of 93 nm in width in resist with initiator of isopropyl thioxanthone (ITX). An 800 nm, 75-MHz fs laser works as the polymerization light and a 532 nm donut mode continuous wave (CW) laser as the depletion light. This technology is potentially useful for fabrication of super resolution nanostructures.

The capability of using Focused Ion Beam (FIB) for milling microchannels is experimentally and theoretically investigated. Microchannel structures are fabricated by a NanoFab 150 FIB machine, using an Arsenic (As²⁺) ion source. A beam current of 5 pA at 90 keV accelerating energy is used. Several microchannel patternings are milled at various dwell times at pixel spacing of 14.5 nm on top of a 60 nm gold-coated silicon wafer. An analytical/numerical model is developed to predict the FIB milling behavior. By comparing with the experimental measurements, the model predictions have been demonstrated to be reliable for guiding and controlling the milling processes.

To overcome the diffraction constraints of traditional optical lithography, the next generation lithographies (NGLs) will utilize any one or more of EUV (extreme ultraviolet), X-ray, electron or ion beam technologies to produce sub-100 nm features. Perhaps the most under-developed and under-rated is the utilization of ions for lithographic purposes. All three ion beam techniques, FIB (Focused Ion Beam), Proton Beam Writing (p-beam writing) and Ion Projection Lithography (IPL) have now breached the technologically difficult 100 nm barrier, and are now capable of fabricating structures at the nanoscale. FIB, p-beam writing and IPL have the flexibility and potential to become leading contenders as NGLs.

The three ion beam techniques have widely different attributes, and as such have their own strengths, niche areas and application areas. The physical principles underlying ion beam interactions with materials are described, together with a comparison with other lithographic techniques (electron beam writing and EUV/X-ray lithography). IPL follows the traditional lines of lithography, utilizing large area masks through which a pattern is replicated in resist material which can be used to modify the near-surface properties. In IPL, the complete absence of diffraction effects coupled with ability to tailor the depth of ion penetration to suit the resist thickness or the depth of modification are prime characteristics of this technique, as is the ability to pattern a large area in a single brief irradiation exposure without any wet processing steps. p-beam writing and FIB are direct write (maskless) processes, which for a long time have been considered too slow for mass production. However, these two techniques may have some distinct advantages when used in combination with nanoimprinting and pattern transfer. FIB can produce master stamps in any material, and p-beam writing is ideal for producing three-dimensional high-aspect ratio metallic stamps of precise geometry. The transfer of large scale patterns using nanoimprinting represents a technique of high potential for the mass production of a new generation of high area, high density, low dimensional structures. Finally a cross section of applications are chosen to demonstrate the potential of these new generation ion beam nanolithographies.

The progress made to resolve challenges met in using deep UV lithography for batch fabrication of pillar type nano-photonic crystals is described, using data from experiments carried out based on two degrees, full factorial design of experiments and subsequently processed using variance analysis. A binary mask without phase shift features was used to obtain information on effects of lithographic parameters such as antireflection coatings, resist preparation recipes, exposure latitude and depth of focus biases. The results derived hence enabled successful derivations of high quality arrays of dense nano-pillars.

Experimental results and techniques developed for time multiplexed deep reactive ion etching of nano-photonic crystals are presented. Specifically, the high aspect ratio pillar type two-dimensional photonic crystal (PhC) structure on silicon is fabricated and studied for its high potential in application to lightwave circuits and also for discussion of the many unique challenges involved in its fabrication process as opposed to standard larger scale devices. In the experiments, patterns of nano-dots were first obtained using deep UV lithography and transferred to a silicon oxide hardmask prior to DRIE processing. The iteration of DRIE experiments with varying process parameters then allowed for a characterization of the varying impact of each etching parameter such as coil/ platen/ etch power, multiplexing cycling gas flows and timing patterns etc. After much optimization of sidewall etch angle and also reduction of the scalloping effect, the latest result obtained for such nano-pillar type PhC designed for application in communication is derived to have a high AR of 33.

Unique features and benefits of the plasma-aided nanofabrication are considered by using the "plasma-building block" approach, which is based on plasma diagnostics and nanofilm characterization, cross-referenced by numerical simulation of generation and dynamics of building blocks in the gas phase, their interaction with nanostructured surfaces, and ab initio simulation of chemical structure of relevant nanoassemblies. The examples include carbon nanotip microemitter structures, semiconductor quantum dots and nanowires synthesized in the integrated plasma-aided nanofabrication facility.

We propose a model on the interface constrained growth in a-SiN_x/a-Si:H/a-SiN_x sandwich structures to make uniform nc-Si grains. Based on the classical growth thermodynamic theory, we study quantitatively the effect of the interface and shape of the nc-Si on the crystal growth in relation to the Gibbs free energy. From our model, we have theoretically determined the critical a-Si sublayer thickness of 34 nm for the interface constrained growth and interpreted the increase of the crystallization temperature in the ultra thin a-Si sublayer. In order to examine the model, a series of samples of a-SiN_x/a-Si:H/a-SiN_x with a-Si sublayer thickness from 2 nm to 40 nm were fabricated and then annealed at 1000°C, for 30, 120, and 240 min, respectively. The results of microstructure characterization supported our model and indicated that the critical a-Si sublayer thickness is between 20 nm and 40 nm which is coincidence with the theoretical value estimated from our model.

Recently it has been elaborated an approach to decrease depth of diffusive- and implanted-junction rectifiers by manufacturing the rectifiers in a semiconductor heterostructure and optimization of annealing of dopant and radiation defects. At the same time with decreasing of depth of the p-n-junction homogeneity of dopant distribution in doped area increases. In this paper we analyzed possibility to increase both the effects at one time by radiation processing of materials of the heterostructure.

Aquatic pteridophyte (Azolla sp.) was taken to assess its potential to synthesize the metal (Au) nanoparticles. The synthesized particles were characterized using X-ray, UV-visible, scanning and transmission electron microscopy analyses. Nanoparticles almost spherical in shape having the sizes of 5–17nm are found. UV-visible study revealed the surface plasmon resonance at 538nm. Responsible phytochemicals for the transformation were principally phenolics, tannins, anthraquinone glycosides and sugars present abundantly in the plant thereby bestowing it adaptive prodigality. Also, the use of Azolla sp. for the synthesis of gold nanoparticles offers the benefit of eco-friendliness.

Noble metal nanoparticles (NPs) have unique optical, electronic and catalytic properties. Dome-like gold (Au) NPs having a size as small as $\sim 16$nm and a high density of $\sim 10^{11}$cm${}^{-2}$ were prepared by very high frequency (VHF) hydrogen (H${}_2)$ plasma-assisted radio frequency magnetron sputtering (RFMS) technique. The influence of RF power and sputtering time on the morphology and structure of islands-like Au nanostructures (NSs) were determined. Besides, optimum sputtering sample (OSS) was treated by VHF H₂ plasma technique to fabricate dense Au NPs with great uniformity. Prepared samples were studied by atomic force microscope (AFM), energy dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscope (HR-TEM). AFM images of the sputtering samples show a good density of islands-like Au NSs ($\sim 10^{10}$cm${}^{-2})$ with relatively homogeneous distribution. VHF H₂ plasma treatment dependent alterations in the surface morphology of the OSS (shape, size, distribution, number density and average surface roughness) were clearly manifested in the AFM images. EDX spectra disclosed prominent Au peaks highly sensitive to the H₂ plasma treatment. Our novel fabrication method may contribute to the development of Au NPs based nanodevices.

Nanotechnology is vital to the fabrication of integrated circuits, memory devices, display units, biochips and biosensors. Scanning probe microscope (SPM) has emerged to be a unique tool for materials structuring and patterning with atomic and molecular resolution. SPM includes scanning tunneling microscopy (STM) and atomic force microscopy (AFM). In this chapter, we selectively discuss the atomic and molecular manipulation capabilities of STM nanolithography. As for AFM nanolithography, we focus on those nanopatterning techniques involving water and/or air when operated in ambient. The typical methods, mechanisms and applications of selected SPM nanolithographic techniques in nanoscale structuring and fabrication are reviewed.

EUV lithography is the exposure technology in which even 15 nm node which is the limit of Si device can be achieved. Unlike the conventional optical lithography, this technology serves as a reflection type optical system, and a multilayer coated mirror is used. Development of manufacturing equipment is accelerated to aim at the utilization starting from 2011. The critical issues of development are the EUV light source which has the power over 115 W and resist with high sensitivity and low line edge roughness (LER).

X-ray lithography with synchrotron radiation is an important nanolithographic tool which has unique advantages in the production of high aspect ratio nanostructures. The optimum synchrotron radiation spectrum for nanometer scale X-ray lithography is normally in the range of 500 eV to 2 keV. In this paper, we present the main methods, equipment, process parameters and preliminary results of nanofabrication by proximity X-ray lithography within the nanomanufacturing program pursued by Singapore Synchrotron Light Source (SSLS). Nanostructures with feature sizes down to 200 nm and an aspect ratio up to 10 have been successfully achieved by this approach.

This article reviews the progress made in the sub-10 nm electron beam patterning of metal oxides over the last thirty years. The patterning of inorganic resists began with metal halides, they were soon taken over by metal oxides due to their excellent environmental stability. However, these inorganic materials, both halides and oxides, suffered from the requirement of very steep dose, thus rendering them useless for practical applications. This gave way to highly electron beam-sensitive stabilized metal alkoxides and metal naphthenates, with sensitively close to conventional electron beam resists such as poly(methylmethacrylate) (PMMA) and calixarene. Furthermore, they show excellent line edge roughness characteristics at sub-10 nm scale, which is currently unmatched by any other electron beam resist. Recent applications of these resists such as an etch mask and their suitability as gate oxides will be highlighted.