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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.

Microelectronic fabrication of Si typically involves high-temperature or high-energy processes. For instance, wafer fabrication, transistor fabrication, and silicidation are all above 500°C. Contrary to that tradition, we believe low-energy processes constitute a better alternative to enable the industrial application of single-molecule devices based on 2D materials. The present work addresses the postsynthesis processing of graphene at unconventional low temperature, low energy, and low pressure in the poly methyl-methacrylate- (PMMA-) assisted transfer of graphene to oxide wafer, in the electron-beam lithography with PMMA, and in the plasma patterning of graphene with a PMMA ribbon mask. During the exposure to the oxygen plasma, unprotected areas of graphene are converted to graphene oxide. The exposure time required to produce the ribbon patterns on graphene is 2 minutes. We produce graphene ribbon patterns with ∼50 nm width and integrate them into solid state and liquid gated transistor devices.

Field-effect transistor (FET) sensors based on reduced graphene oxide (rGO) for detecting chemical species provide a number of distinct advantages, such as ultra-sensitivity, label-free, and real-time response. However, without a passivation layer, channel materials directly exposed to an ionic solution could generate multiple signals from ionic conduction through the solution droplet, doping effect, and gating effect. Therefore, a method that provides a passivation layer on the surface of rGO without degrading device performance will significantly improve device sensitivity, in which the conductivity changes solely with the gating effect. In this work, we report rGO FET sensor devices with Hg2+-dependent DNA as a probe and the use of an Al2O3 layer to separate analytes from conducting channel materials. The device shows good electronic stability, excellent lower detection limit (1 nM), and high sensitivity for real-time detection of Hg2+ in an underwater environment. Our work shows that optimization of an rGO FET structure can provide significant performance enhancement and profound fundamental understanding for the sensor mechanism. Keywords: Field-effect transistor, Graphene oxide, Au nanoparticle, Passivation layer

This article reports that it is possible to make multifunctional sensing devices with ZnO infiltrated polymers while the sensing interactions could occur throughout the polymer. As such, we find that infiltrated devices with SU-8 polymer can result in highly sensitive UV sensors. Mesh dielectric core devices were found to make sensitive gas sensors with a better than 5 ppm sensitivity for formaldehyde and NO2. A new type of p-n junction device is further demonstrated that is sensitive to UV illumination, thus making it an enhanced UV sensor. Sensing devices relying on volume interactions, such as light absorption, can significantly benefit from the infiltrated polymer. In contrast, devices that rely on surface interactions, such as gas sensors, do not gain performance in any significant way with or without the infiltrated polymer.

We demonstrate a practical sensing platform, consisting of SnO2 nanoparticle-decorated semiconducting single-walled carbon nanotubes assembled on gold electrodes via a dielectrophoretic process, for highly sensitive CO detection with fast response at room temperature. The highest sensitivity obtained was 0.27 and the response time was ˜2 s for 100 ppm CO detection. The lower detection limit was ˜1 ppm. These results indicate that the sensing performance of our device is among the best of CO sensors implemented with SWNTs. Further, we observed a significant increase in sensitivity to 0.67 after subjecting the device to an electrical breakdown at 8 V. We also proposed a theoretical model to reveal the relationship between the sensitivity and the gas concentration. The new model not only resulted in a nice fit to our data, but also allowed us to estimate the contact resistance between an individual SWNT and the gold electrodes. [ABSTRACT FROM AUTHOR]

Etch resistance of two commonly used lithography resists is increased significantly by sequential infiltration synthesis (SIS). Exposing films to trimethyl-aluminum and water with long dosage times infiltrates the bulk of the film with alumina, which renders them dramatically more resistant to plasma etching with no degradation to the patterns. Enhanced etch resistance eliminates the need for an intermediate hard mask and the concomitant costs and pattern fidelity losses. Moreover, by allowing for thinner resist films, this approach can improve the final pattern resolution. [ABSTRACT FROM AUTHOR]

Poly methyl methacrylate (PMMA) is the most widely used resist in electron beam lithography. This paper reports on a lithography and Raman spectroscopy study of development characteristics of PMMA in methanol, ethanol and isopropanol mixtures with water as developers. We have found that ethanol/water mixtures at a 4:1 volume ratio are an excellent, high resolution, non-toxic developer for exposed PMMA. We have also found that the proper methodology to use so that contrast data can be compared to techniques used in polymer science is not to rinse the developed resist but to immediately dry with nitrogen. Our results show how powerful simple lithographic techniques can be used to study ternary polymer solvent solutions when compared to other techniques used in the literature. Raman data show that both tightly bonded –OH groups and non-hydrogen bonded –OH groups play a role in the development of PMMA. Tightly hydrogen bonded –OH groups show pure Lorentzian Raman absorption only in the concentration ranges where ethanol/water and IPA/water mixtures are effective developers of PMMA, pointing to possible ordering or reduced amorphization due to the liquid state. The impact of understanding these interactions may open doors to a new developers of other electron beam resists that can reduce the toxicity of the waste stream. [ABSTRACT FROM AUTHOR]

The optical properties of BaTiO3 two dimensional photonic crystal (PhC) nanocavities were investigated. Two types of nanocavities consisting of dopants and vacancies with PhC periodicities ranging from 200 to 550 nm were evaluated. The images from laser scanning confocal microscopy show the optical scattering of the PhC cavities is highly wavelength dependent. An optical intensity reversal is observed when the wavelength of probe light shifts by 29 nm. Meanwhile, intensity contrast between the nanocavity and its adjacent PhCs is enhanced as the PhC periodicity becomes shorter than the probe wavelength. To determine the photonic band structures fluorescence from dye covered PhCs were imaged and analyzed. A strong enhancement of fluorescence is observed for the PhC with a period of 200 nm. Upon comparison to the 2D finite difference time domain calculations, the enhancement is attributed to strong light localization within the PhC nanocavity. As a result, the in-plane lightwave propagation is prohibited that results in an increase in the vertical light scattering. [ABSTRACT FROM AUTHOR]