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We demonstrated here for the first time that the stereochemistry of polylactide (PLA) blocks affected the assembly behaviors of PS

An alternative method to fabricate T- and Γ-gates used for special geometry compound semiconductor high electron mobility transistors is presented. This method utilizes an acrylate/methylstyrene triple resist stack, a single ternary developer consisting of an acetate/alcohol/water mixture, and a proximity effect correction (PEC) image superposition approach that treats the exposed regions in the different resists as independent images and combines them afterward with weighted factors. In the past, most available options required multiple developers or ebeam exposures to form the resist structure of the gate. In this paper, we present a single developer capable of discriminating among three different resists to form the optimal structure for T- and Γ-gates. The PEC image superposition approach approximates that the exposed regions in each resist layer (or image) can be PEC corrected independently from the other images. The use of a gap between images allows for critical dimension control as image edges are not double exposed due to beam spread. Following gap formation and PEC, the corrected images are superimposed on each other after selectively removing areas of common exposure, using the highest dose as the determining dose. This allows a flexible means to accurately provide PEC to complex structures beyond “simple” T-gates and Γ-gates, as demonstrated in this paper.

Resistance switching in metal-insulator-metal structures has been extensively studied in recent years for use as synaptic elements for neuromorphic computing and as nonvolatile memory elements. However, high switching power requirements, device variabilities, and considerable trade-offs between low operating voltages, high on/off ratios, and low leakage have limited their utility. In this work, we have addressed these issues by demonstrating the use of ultraporous dielectrics as a pathway for high-performance resistive memory devices. Using a modified atomic layer deposition based technique known as sequential infiltration synthesis, which was developed originally for improving polymer properties such as enhanced etch resistance of electron-beam resists and for the creation of films for filtration and oleophilic applications, we are able to create ∼15 nm thick ultraporous (pore size ∼5 nm) oxide dielectrics with up to 73% porosity as the medium for filament formation. We show, using the Ag/Al

Photonic ring resonator arrays used as notch filters are a promising novel solution to improve the signal-to-noise ratio of ground-based astronomical observations by suppressing OH emission lines in the near-infrared (NIR) wavelength range (0.9-2.5 μm). We aim to fabricate a series of ring resonators connected by a waveguide, each with its resonance wavelength and full-width-half-maximum (FWHM) matched with one of the OH emission lines.

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. )e submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract DE-AC02-06CH11357. )e U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the government. Funding text #2 )e Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357. )e authors also acknowledge financial support from Argonne National Laboratory’s Laboratory-Directed Research and Development Strategic Initiative. Revisión por pares

A Permalloy (Py) thin film enabled tunable 3-D solenoid inductor is designed and fabricated. The special configuration of magnetic core is discussed and by selectively patterning Py thin film, the proposed tunable inductor can work at frequency up to several GHz range. The inductance of the solenoid inductor can be electrically tuned by dc current and the tunability is above 10%. Utilizing the implemented Py enabled tunable solenoid inductor and Lead Zirconate Titanate thin film enabled metal-insulator-metal capacitor, a compact fully electrically tunable lumped elements phase shifter is achieved. The tunable phase shifter has both inductive and capacitive tunability and the dual tunability significantly improves the tuning range and design flexibility. Moreover, the dual tunability is able to retain the equivalent characteristic impedance of the device in the process of the phase being tuned. The phase of the device can be tuned by fully electrical methods and when dc current and dc voltage are provided, the length normalized phase tunability is up to 210°/cm.

In exploiting topological defects of liquid crystals as the targeting sites for trapping colloidal objects, previous work has relied on topographic features with uniform anchoring to create defects, achieving limited density and spacing of particles. We report a generalizable strategy to create topological defects on chemically patterned surfaces to assemble particles in precisely defined locations with a tunable interparticle distance at nanoscale dimensions. Informed by experimental observations and numerical simulations that indicate that liquid crystals, confined between a homeotropic-anchoring surface and a surface with lithographically defined planar-anchoring stripes in a homeotropic-anchoring background, display splay-bend deformation, we successfully create pairs of defects and subsequently trap particles with controlled spacing by designing patterns of intersecting stripes aligned at 45° with homeotropic-anchoring gaps at the intersections. Application of electric fields allows for dynamic control of trapped particles. The tunability, responsiveness, and adaptability of this platform provide the opportunities for assembly of colloidal structures toward functional materials.

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.

Characterization of the three-dimensional (3D) structure in directed self-assembly (DSA) of block copolymers is crucial for understanding the complex relationships between the guiding template and the resulting polymer structure so DSA could be successfully implemented for advanced lithography applications. Here, we combined scanning transmission electron microscopy (STEM) tomography and coarse-grain simulations to probe the 3D structure of P2VP-b-PS-b-P2VP assembled on prepatterned templates using solvent vapor annealing. The templates consisted of nonpreferential background and raised guiding stripes that had PS-preferential top surfaces and P2VP-preferential sidewalls. The full 3D characterization allowed us to quantify the shape of the polymer domains and the interface between domains as a function of depth in the film and template geometry and offered important insights that were not accessible with 2D metrology. Sidewall guiding was advantageous in promoting the alignment and lowering the roughness of the P2VP domains over the sidewalls, but incommensurate confinement from the increased topography could cause roughness and intermittent dislocations in domains over the background region at the bottom of the film. The 3D characterization of bridge structures between domains over the background and breaks within domains on guiding lines sheds light on possible origins of common DSA defects. The positional fluctuations of the PS/P2VP interface between domains showed a depth-dependent behavior, with high levels of fluctuations near both the free surface of the film and the substrate and lower fluctuation levels in the middle of the film. This research demonstrates how 3D characterization offers a better understanding of DSA processes, leading to better design and fabrication of directing templates.

We have investigated the growth of zinc oxide in a polymer matrix by sequential infiltration synthesis (SiS). The atomic cycle-by-cycle self-terminating reaction growth investigation was done using photoluminescence (PL), Raman, and X-ray photoemission spectroscopy (XPS). Results show clear differences between Zn atom configurations at the initial stages of growth. Mono Zn atoms (O–Zn and O–Zn–O) exhibit pure UV emission with little evidence of deep level oxygen vacancy states (VO). Dimer Zn atoms (O–Zn–O–Zn and O–Zn–O–Zn–O) show strong UV and visible PL emission from VO states 20 times greater than that from the mono Zn atom configuration. After three precursor cycles, the PL emission intensity drops significantly exhibiting first evidence of crystal formation as observed with Raman spectroscopy via the presence of longitudinal optical phonons. We also report a first confirmation of energy transfer between polymer and ZnO where the polymer absorbs light at 241 nm and emits at 360 nm, which coincides with...

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.

Optical trapping has been implemented in many areas of physics and biology as a noncontact sample manipulation technique to study the structure and dynamics of nano- and mesoscale objects. It provides a unique approach for manipulating microscopic objects without inducing undesired changes in structure. Combining optical trapping with hard X-ray microscopy techniques, such as coherent diffraction imaging and crystallography, provides a nonperturbing environment where electronic and structural dynamics of an individual particle in solution can be followed in situ. It was previously shown that optical trapping allows the manipulation of micrometer-sized objects for X-ray fluorescence imaging. However, questions remain over the ability of optical trapping to position objects for X-ray diffraction measurements, which have stringent requirements for angular stability. Our work demonstrates that dynamic holographic optical tweezers are capable of manipulating single micrometer-scale anisotropic particles in a microfluidic environment with the precision and stability required for X-ray Bragg diffraction experiments-thus functioning as an "optical goniometer." The methodology can be extended to a variety of X-ray experiments and the Bragg coherent diffractive imaging of individual particles in solution, as demonstrated here, will be markedly enhanced with the advent of brighter, coherent X-ray sources.

Artificial polariton bandgaps at infrared frequencies are investigated by exploiting the strong coupling of electromagnetic waves with induced electric dipoles in two-dimensional (2D) indium tin oxide nanorod arrays (ITO-NRAs). The electric dipoles originate from the collective oscillations of free electrons within the individual ITO nanorods undergoing plasmonic resonance. Controlling the near-field interactions among the neighboring electric dipoles allows for manipulation of the collective polariton modes that are manifested as a polariton bandgap. A theoretical model is developed to understand the coupled phenomena underlying the unique characteristics of plasmon–polariton bandgaps. With high-degree geometric control of the ITO-NRAs, it is experimentally demonstrated that reducing the spacing between ITO nanorods in a square array strengthens the near-field interactions and thus results in a redshift as well as broadening of the polariton bandgap. Furthermore, arranging ITO-NRAs in a rectangular lattice breaks the symmetry with respect to the principle axis, which leads to a splitting of the collective polariton modes owing to the competition between the quasi-longitudinally and quasi-transversely coupled plasmon–polariton modes. The work highlights the use of a classical dipole coupling method for scaling polariton bandgaps to the infrared in artificial plasmonic lattices, thereby offering a new design dimension for infrared sensing, absorbers, and optical communications.

Active control of light is important for photonic integrated circuits, optical switches, and telecommunications. Coupling light with acoustic vibrations in nanoscale optical resonators offers optical modulation capabilities with high bandwidth and small footprint. Instead of using noble metals, here we introduce indium-tin-oxide nanorod arrays (ITO-NRAs) as the operating media and demonstrate optical modulation covering the visible spectral range (from 360 to 700 nm) with ∼20 GHz bandwidth through the excitation of coherent acoustic vibrations in ITO-NRAs. This broadband modulation results from the collective optical diffraction by the dielectric ITO-NRAs, and a high differential transmission modulation up to 10% is achieved through efficient near-infrared, on-plasmon-resonance pumping. By combining the frequency signatures of the vibrational modes with finite-element simulations, we further determine the anisotropic elastic constants for single-crystalline ITO, which are not known for the bulk phase. This technique to determine elastic constants using coherent acoustic vibrations of uniform nanostructures can be generalized to the study of other inorganic materials.

We demonstrated here for the first time that the stereochemistry of polylactide (PLA) blocks affected the assembly behaviors of PS-b-PLA on chemical patterns. Two PS-b-PLA block copolymers, where the PLA block is either racemic (PDLLA) or left-handed (PLLA), were synthesized and directed to assemble on chemical patterns with a wide range of Ls/L0. PS-b-PDLLA was stretched up to 70% on chemical patterns, while PS-b-PLLA was only stretched by 20%. The assembly behavior of PS-b-PDLLA was different from AB diblock copolymer, but similar to that of ABA triblock copolymer. The high stretchability might be attributed to the formation of stereocomplexes in PDLLA blocks. Compared to ABA triblock copolymers, stereocomplexed diblock copolymers have much faster assembly kinetics. This observation provides a new concept to achieve large process windows by the introduction of specific interactions, for example, H-bonding, supramolecular interaction, and sterecomplexation, between polymer chains.

Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X–) groups, which are anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X– = chlori...

The ability to construct heterostructures that consist of layered transition metal dichalcogenides materials (MX2) in a controlled fashion provides an attractive solution for materials design and device applications. For nanotechnology applications it is important to control the shape, geometry and precise position of the grown heterostructure assemblies on a variety of substrates. In this study, we developed a “direct writing” technique to fabricate arrays of WS2/MoS2 and MoS2/WS2/MoS2 heterostructures at predefined locations on a silicon substrate in a controlled fashion. Water based precursor inks were implemented to ensure the formation of quality heterostructure surfaces which are free of residual polymer contaminants. With this technique we demonstrate an attractive and scalable technology with unique capabilities for precise growth of dissimilar MX2 materials, layered either in a vertical or lateral arrangement.

Geometric frustration emerges when local interaction energies in an ordered lattice structure cannot be simultaneously minimized, resulting in a large number of degenerate states. The numerous degenerate configurations may lead to practical applications in microelectronics, such as data storage, memory and logic. However, it is difficult to achieve extensive degeneracy, especially in a two-dimensional system. Here, we showcase in-situ controllable geometric frustration with massive degeneracy in a two-dimensional flux quantum system. We create this in a superconducting thin film placed underneath a reconfigurable artificial-spin-ice structure. The tunable magnetic charges in the artificial-spin-ice strongly interact with the flux quanta in the superconductor, enabling the switching between frustrated and crystallized flux quanta states. The different states have measurable effects on the superconducting critical current profile, which can be reconfigured by precise selection of the spin ice magnetic state through application of an external magnetic field. We demonstrate the applicability of these effects by realizing a reprogrammable flux quanta diode. The tailoring of the energy landscape of interacting 'particles' using artificial-spin-ices provides a new paradigm for the design of geometric frustration, which allows us to control new functionalities in other material systems, such as magnetic skyrmions, electrons/holes in two-dimensional materials and topological insulators, as well as colloids in soft materials., 32 pages, 14 figures

Photonic ring resonators used as wavelength notch filters are a promising novel solution to enable astronomical instruments to remove the signal from atmospheric OH emission in the near-infrared wavelength range. We derive design requirements from theory and finite difference time domain simulations. We find rings with radii less than 10 microns provide an adequate free spectral range for silicon nitride abd less than 3 microns for silicon. One challenge for this application is the requirement for many rings in series to suppress particular wavelengths within 0.2nm. We report progress in fabricating both silicon and silicon nitride rings for OH suppression.

New device concepts related to both computing and biological function emulation are emerging rapidly based upon the electronic insulator-to-metal transition (E-IMT) effect that some oxides, such as VO2, exhibit. However, the experimental E-IMT devices to-date are limited to an ON/OFF ratio of ∼102, resulting in a small and inadequate dynamic range in device operation. In addition, the voltage that drives the E-IMT is high, typically above 1 V. In this paper, we investigate the physics and technology toward realizing both high ON/OFF and low-voltage E-IMT devices. We show that, the ON/OFF ratio, critical E-IMT voltage, and device reliability are closely coupled. A predictive model is developed and shows that, for reliable operation, the maximum ON/OFF ratio of an E-IMT device should follow a square-root relation with the strength of the thermally driven insulator-to-metal transition (T-IMT). This new design rule is verified by systematic experiments using prototypical VO2 E-IMT devices. Through this study, we achieve a record value of reliable E-IMT with an ON/OFF ratio of 3.5×103 at 1.2 V — greater than 10x improvement over the previous state-of-the-art. A record low voltage of IMT switching at 0.3 V (ON/OFF ratio = 20) is also demonstrated. The proposed universal design rule is widely applicable for a range of emerging applications based on E-IMT devices. As an experimental example, the E-IMT based transistors show an ultra-steep subthreshold swing ( 103.

We report in this complementary theoretical–experimental work the effect of gating on the electron transport of graphene ribbons when exposed to very low concentration of europium in an aqueous solution. We find a direct correlation between the level of concentration of europium ions in the solvent and the change in electron transport in graphene, observing a change of up to 3 orders of magnitude at the lowest level of concentration tested (0.1 mM), suggesting a possibility that graphene ribbons can be used for detecting very low concentrations of europium in liquid solutions.

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

A concept of tunable transmission line (TL) enabled with nanopatterned ferromagnetic permalloy (Py) and ferroelectric lead zirconium titanate (PZT) thin films is presented. The permittivity (e r ) of PZT is electrical tunable with dc voltage, and the permeability (μ r ) of Py is electrical tunable with dc current, thus simultaneous electric tunable capacitance and inductance capability are provided for the proposed TL. The proposed TL has been fabricated and compared with a regular line without nanofilm patterns. Py is patterned with the dimensions of 10 μm × 150 nm and thickness of 100 nm for high built-in anisotropy field. The ferromagnetic resonant frequency is measured to be 6.3 GHz. Compared with the regular TL, the implemented TL has only generated 0.05 dB additional insertion loss at 4 GHz. The electrical tunability of both the capacitance and the inductance has been demonstrated for the first time. By applying the varied dc current (0-150 mA) and the dc voltage (0-20 V), measured results have shown that the proposed line can provide 90° phase shift from 3.75 to 4 GHz with the fixed characteristic impedance. The continuous tuning of the characteristics impedance from 59 to 61 Ω under suitable bias conditions shows its promise as an impedance matching network. Tunable range of both the phase shifter and the impedance matching network can be further increased with thicker and multilayer films.

We realize a $\Lambda$ system in a superconducting circuit, with metastable states exhibiting lifetimes up to 8\,ms. We exponentially suppress the tunneling matrix elements involved in spontaneous energy relaxation by creating a "heavy" fluxonium, realized by adding a capacitive shunt to the original circuit design. The device allows for both cavity-assisted and direct fluorescent readout, as well as state preparation schemes akin to optical pumping. Since direct transitions between the metastable states are strongly suppressed, we utilize Raman transitions for coherent manipulation of the states., Comment: Total of 10 pages. 5 pages in main tex, and 5 in supplement. Total of 9 figures in entire document

Ring resonators provide a means of filtering specific wavelengths from a waveguide, and optionally dropping the filtered wavelengths into a second waveguide. Both of these features are potentially useful for astronomical instruments. In this paper we focus on their use as notch filters to remove the signal from atmospheric OH emission lines from astronomical spectra, however we also briefly discuss their use as frequency combs for wavelength calibration and as drop filters for Doppler planet searches. We derive the design requirements for ring resonators for OH suppression from theory and finite difference time domain simulations. We find that rings with small radii (0.9), but further optimisation is required to achieve higher Q and deeper notches, with current devices having $Q \approx 4000$ and $\approx 10$ dB suppression. The overall prospects for the use of ring resonators in astronomical instruments is promising, provided efficient fibre-chip coupling can be achieved., Submitted to Optics Express feature issue on Recent Advances in Astrophotonics (27 pages, 20 figs)

Integrated optics has the potential to play a transformative role in astronomical instrumentation. It has already made a significant impact in the field of optical interferometry, through the use of planar waveguide arrays for beam combination and phase-shifting. Additionally, the potential benefits of micro-spectrographs based on array waveguide gratings have also been demonstrated. Here we examine a new application of integrated optics, using ring resonators as notch filters to remove the signal from atmospheric OH emission lines from astronomical spectra. We also briefly discuss their use as frequency combs for wavelength calibration and as drop filters for Doppler planet searches. We discuss the theoretical requirements for ring resonators for OH suppression. We find that small radius (< 10 μm), high index contrast (Si or Si3N4) rings are necessary to provide an adequate free spectral range. The suppression depth, resolving power, and throughput for efficient OH suppression can be realised with critically coupled rings with high self-coupling coefficients. We report on preliminary laboratory tests of our Si and Si3N4 rings and give details of their fabrication. We demonstrate high self-coupling coefficients (> 0:9) and good control over the free spectral range and wavelength separation of multi-ring devices. Current devices have Q ≈ 4000 and ≈ 10 dB suppression, which should be improved through further optimisation of the coupling coefficients. The overall prospects for the use of ring resonators in astronomical instruments is promising, provided efficient fibre-chip coupling can be achieved.

We have developed a platform-independent software package for designing nanometer scaled device architectures. The Nanolithography Toolbox is applicable to a broad range of design tasks in the fabrication of microscale and nanoscale devices.

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.

We present a systematic study of light scattering from indium-tin-oxide (ITO) nanorods in the near-infrared with a special focus on the resonant coupling of plasmonic transverse mode and photonic modes in 2-D periodic arrays. Using theoretical analysis combined with simulations, a set of experiments has been designed to study such interactions. Near-field mapping from the simulations shows a strong interaction of localized surface plasmon resonances (LSPR) with a photonic resonance; together they explain the scattering phenomenon observed in our experiments carried out in the far field. We observed the shift of LSPR as the plasma frequency was varied, resulting in a modification of the spectral shape. Utilizing the high aspect ratios of the ITO nanorods, the LSPR strength can be turned on and off by the polarization of the incident light.

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.

Transfer of graphene, grown by Chemical Vapor Deposition (CVD), to a substrate of choice, typically involves deposition of a polymeric layer (typically, poly(methyl methacrylate, PMMA or polydimethylsiloxane, PDMS). These polymers are quite hard to remove without leaving some residues behind. Here we study a transfer of graphene with a protective thin oxide layer. The thin oxide layer is grown by Atomic Deposition Layer (ALD) on the graphene right after the growth stage on Cu foils. One can further aid the oxide-graphene transfer by depositing a very thin polymer layer on top of the composite (much thinner than the usual thickness) following by a more aggressive polymeric removal methods, thus leaving the graphene intact. We report on the nucleation growth process of alumina and hafnia films on the graphene, their resulting strain and on their optical transmission. We suggest that hafnia is a better oxide to coat the graphene than alumina in terms of uniformity and defects., Comment: 13 pgs, 13 figures

Future optical systems will require electro-optic (EO) modulators with bandwidths of 100 GHz. For high-speed modulation, a photonic crystal (PhC) waveguide modulator using a ferroelectric thin film has been proposed. Here we report on the design, fabrication and properties of optical intensity modulator and its microwave frequency dependence. The 1.5 mm long ${\rm BaTiO}_{3}$ PhC modulator has a figure-of-merit of 2.1 ${\rm V}\cdot{\hbox {cm}}$ drive voltage-length product, $>$ 50 GHz 3 dB bandwidth at an operating wavelength of 1560 nm.

Secondary electrons play critical roles in several imaging technologies, including extreme ultraviolet (EUV) lithography. At longer wavelengths of light (e.g. 193 and 248 nm), the photons are directly involved in the photochemistry occurring during photolysis. EUV light (13.5 nm, 92 eV), however, first creates a photoelectron, and this electron, or its subsequent daughter electrons create most of the chemical changes that occur during exposure. Despite the importance of these electrons, the details surrounding the chemical events leading to acid production remain poorly understood. Previously reported experimental results using high PAG-loaded resists have demonstrated that up to five or six photoacids can be generated per incident photon. Until recently, only electron recombination events were thought to play a role in acid generation, requiring that at least as many secondary electrons are produced to yield a given number of acid molecules. However, the initial results we have obtained using a Monte Carlo-based modeling program, LESiS, demonstrate that only two to three secondary electrons are made per absorbed EUV photon. A more comprehensive understanding of EUV-induced acid generation is therefore needed for the development of higher performance resists

This article introduces in archival form the Nanolithography Toolbox, a platform-independent software package for scripted lithography pattern layout generation. The Center for Nanoscale Science and Technology (CNST) at the National Institute of Standards and Technology (NIST) developed the Nanolithography Toolbox to help users of the CNST NanoFab design devices with complex curves and aggressive critical dimensions. Using parameterized shapes as building blocks, the Nanolithography Toolbox allows users to rapidly design and layout nanoscale devices of arbitrary complexity through scripting and programming. The Toolbox offers many parameterized shapes, including structure libraries for micro- and nanoelectromechanical systems (MEMS and NEMS) and nanophotonic devices. Furthermore, the Toolbox allows users to precisely define the number of vertices for each shape or create vectorized shapes using Bezier curves. Parameterized control allows users to design smooth curves with complex shapes. The Toolbox is applicable to a broad range of design tasks in the fabrication of microscale and nanoscale devices.

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.

In extreme ultraviolet (EUV) lithography, 92 eV photons are used to expose photoresists. Typical EUV resists are organic-based and chemically amplified using photoacid generators (PAGs). Upon exposure, PAGs produce acids which catalyze reactions that result in changes in solubility. In EUV lithography, photo- and secondary electrons (energies of 10- 80 eV) play a large role in PAG acid-production. Several mechanisms for electron-PAG interactions (e.g. electron trapping, and hole-initiated chemistry) have been proposed. The aim of this study is to explore another mechanism – internal excitation – in which a bound PAG electron can be excited by receiving energy from another energetic electron, causing a reaction that produces acid. This paper explores the mechanism of internal excitation through the analogous process of electron-induced fluorescence, in which an electron loses energy by transferring that energy to a molecule and that molecule emits a photon rather than decomposing. We will show and quantify electron-induced fluorescence of several fluorophores in polymer films to mimic resist materials, and use this information to refine our proposed mechanism. Relationships between the molecular structure of fluorophores and fluorescent quantum yield may aid in the development of novel PAGs for EUV lithography.

Optimizing the photochemistry of extreme ultraviolet (EUV) photoresists should provide faster, more efficient resists which would lead to greater throughput in manufacturing. The fundamental reaction mechanisms in EUV resists are believed to be due to interactions with energetic electrons liberated by ionization. Identifying the likelihood (or cross section) of how these photoelectrons interact with resist components is critical to optimizing the performance of EUV resists. Chemically amplified resists utilize photoacid generators (PAGs) to improve sensitivity; measuring the cross section of electron induced decomposition of different PAGs will provide insight into developing new resist materials. To study the interactions of photoelectrons generated by EUV absorption, photoresists were exposed to electron beams at energies between 80 and 250 eV. The reactions between PAG molecules and electrons were measured using a mass spectrometer to monitor the levels of small molecules produced by PAG decomposition that outgassed from the film. Comparing the cross sections of a variety of PAG molecules can provide insight into the relationship between chemical structure and reactivity to the electrons in their environments. This research is a part of a larger SEMATECH research program to understand the fundamentals of resist exposures to help in the development of new, better performing EUV resists.

EUV photons expose photoresists by complex interactions including photoionization to create primary electrons (~80 eV), and subsequent ionization steps that create secondary electrons (10-60 eV). The mechanisms by which these electrons interact with resist components are key to optimizing the performance of EUV resists and EUV lithography as a whole. As these photoelectrons and secondary electrons are created, they deposit their energy within the resist, creating ionized atoms along the way. Because many photo- and secondary electrons can escape the resist through the surface, resists can become charged. Charging and energy deposition profiles within the resist may play a role in the sensitivity and line-edge roughness of EUV resists. In this paper, we present computational analysis of charging-influenced electron behavior in photoresists using LESiS (Low energy Electron Scattering in Solids), a software developed to understand and model electron-matter interactions. We discuss the implementation of charge and tracking and the model used to influence electron behavior. We also present the potential effects of charging on EUV and electron beam lithography by investigating secondary electron blur in charging and non-charging models.

For the past several years there have been ongoing efforts to incorporate zinc oxide (ZnO) inside polymethyl methacrylate (PMMA), in the form of nanoparticles or quantum dots, to combine their optical properties for multiple applications. We have investigated a variation of atomic layer deposition (ALD), called sequential infiltration synthesis (SiS), as an alternate method to incorporate ZnO and other oxides inside the polymer. PMMA is a well-known ebeam resist. We can expose and develop patterns useful for photonics or sensing applications first, and then convert them afterwards into a hybrid oxide material with enhanced photonic, or sensing, properties. This is much easier than micromachining films of ZnO or other similar oxides because they are difficult to etch. The amount of ZnO formed inside the polymer film is magnitudes higher than equivalent amount deposited on a flat 2D surface, and the intensity of the photoemission suggests there is an enhancement created by the polymer-ZnO interaction. Photoemission from thin films exhibit photoemission similar to intrinsic ZnO with oxygen vacancies. These vacancies can be removed by annealing the sample at 500°C in an oxygen rich environment. SiS ZnO exhibits unusual photoemission properties for thick polymer films, emitting at excitations wavelengths not found in bulk or standard ZnO. Finally we have shown that patterning the polymer and then doing SiS ZnO treatment afterwards allows modifying or manipulating the photoemission spectra. This opens the doors to novel photonic applications.

The key ingredient of high critical currents in a type-II superconductor is defect sites that 'pin' vortices. Contrary to earlier understanding on nano-patterned artificial pinning, here we show unequivocally the advantages of a random pinscape over an ordered array in a wide magnetic field range. We reveal that the better performance of a random pinscape is due to the variation of its local-density-of-pinning-sites (LDOPS), which mitigates the motion of vortices. This is confirmed by achieving even higher enhancement of the critical current through a conformally mapped random pinscape, where the distribution of the LDOPS is further enlarged. The demonstrated key role of LDOPS in enhancing superconducting critical currents gets at the heart of random versus commensurate pinning. Our findings highlight the importance of random pinscapes in enhancing the superconducting critical currents of applied superconductors., Comment: To appear in Physical Review B

Artificial ices enable the study of geometrical frustration by design and through direct observation. However, it has proven difficult to achieve tailored long-range ordering of their diverse configurations, limiting both fundamental and applied research directions. We designed an artificial spin structure that produces a magnetic charge ice with tunable long-range ordering of eight different configurations. We also developed a technique to precisely manipulate the local magnetic charge states and demonstrate write-read-erase multifunctionality at room temperature. This globally reconfigurable and locally writable magnetic charge ice could provide a setting for designing magnetic monopole defects, tailoring magnonics, and controlling the properties of other two-dimensional materials.