category » Nanotechnology

Figure 2: Comparison of experimental and simulated strain profiles obtained from GPA, NBED, and FEA.  The two simulated strain profiles demonstrate how the revised chemistries seen in the inset improved the FEA model.
Nanoscale Stress State Characterization of InAlN/GaN Nanoribbon HEMT Structures
  • Due to its high band gap energy and superb electronic-carrier mobilities, GaN is fast becoming the material of choice for…


Figure 2: (a) J–V characteristics of the graphene-based PbS QD devices with different polymer interlayers, demonstrating performance comparable to that of an ITO reference cell. (b) J–V characteristics of representative graphene-based P3HT devices with different polymer interlayers, compared with an ITO reference device. Insets in (a) and (b) show SEM cross-section images of the complete devices.
Graphene Cathode-based ZnO Nanowire Hybrid Solar Cells
  • Semiconducting nanowire-based solar cells have gained interest because of their potential to achieve one-dimensional charge transport pathways and large interfacial…


Towards Highly Scaled Gate Length Asymmetrically Strained Ge Nanowire p-MOSFETs
  • Ge nanowires are of interest for future sub-10-nm gate length p-MOSFETs because of the excellent electrostatic control afforded by the…


Figure 2: J-V characteristics under AM1.5G illumination for representative planar (black) and nanowire-based (red) QDPV devices. Incorporating ZnO nanowires boosts the short-circuit current density (JSC) and the power conversion efficiency (PCE) by 50% and 35%, respectively. Black crosses indicate the maximum power point.
ZnO Nanowire Arrays for Enhanced Photocurrent in PbS Quantum Dot Solar Cells
  • Here we demonstrate a solution-processed ordered bulk heterojunction quantum dot (QD) solar cell with AM1.5G power conversion efficiencies of up…


Next-Generation Ultrafast Photo-Triggered Cathodes
  • State-of-the-art ultrafast cathodes are based on the photoelectric effect, where electrons are emitted from a flat surface using ultraviolet (UV)…


High-Current Cold Cathodes with Temporal and Spatial Emission Uniformity
  • Field emission arrays (FEAs) are an attractive alternative to mainstream thermionic cathodes, which are power hungry and require high vacuum…


Microfabricated Ionic Liquid Electrospray Sources with Dense Arrays of Emitters and Carbon Nanotube Flow Control Structures
  • Electrospray is a process to ionize electrically conductive liquids that relies on strong electric fields; charged particles are emitted from…


Figure 2: Experimental nano-TLM resistance of test structures with average contact length of 80 nm. The values of ρc, Rsh, and Rshm are extracted by the 2D nano-TLM model. The insets show the two configurations in the Kelvin measurements.
Nano-scale Metal Contacts for III-V FETs
  • In the last few years, III-V compound semiconductors have emerged as a promising family of materials to replace silicon in…


Figure 1: Brightfield image showing the patterned structure on a silicon substrate. The patterns were defined using ebeam lithography on SU8 resist followed by sputtering of 100 nm of silicon dioxide.
Nano-patterning of J-aggregate Thin Films
  • We show patterning of thin J-aggregate[1] films using nano-imprinting. Unlike the conventional microfabrication techniques, such as direct-write or lift-off processes,…


Figure 1. Large-area (1.5- x 1.5-cm Si/SiO2 substrate) binary nanocrystal superlattices (BNSLs) assembled from 8-nm CdSe/ZnS and 4-nm PbS/CdS core-shell QDs. (a) Fluorescence microscope image (1000x, 595-nm band filter) of BNSLs showing an average grain size of 3.2 um. (b) False color high-resolution transmission microscope (HRTEM) image and small-angle electron diffraction (CL 200 cm) pattern obtained from a single BNSL domain showing a formation of a cub-AB13 structure.
Binary Nanoparticle Superlattices Formed from Highly Luminescent Core-Shell Quantum Dots and Their Photoluminescence Properties
  • Colloidal semiconductor nanocrystals or quantum dots (QDs) offer size-tunable absorption and luminescence spectra, permitting a broad range of applications in…


Figure 1: SEM of Au nanorod array.  The nanorod geometry was tuned to match a longitudinal surface plasmon mode of an Au nanorod, which was excited by 800-nm incident laser beam.
Nanostructured Photocathodes for Compact Coherent X-ray Sources
  • Nanostructured photocathode arrays can be used as the electron sources for the compact coherent X-ray source. Femtosecond laser pulses were…


Figure 2: A plot of external quantum efficiency versus current density, demonstrating the ~50- to 100-fold enhancement in QD-LED performance achieved by replacing core-only PbS QDs (black) with core-shell PbS-CdS QDs (green). The inset is a photograph of an array of five QD-LEDs taken with an infrared camera, with the middle device turned on and emitting at a center wavelength of λ=1242 nm .
High-performance Near-infrared Light-emitting Devices using Core-shell (PbS-CdS) Colloidal Quantum-dots
  • Near-infrared light sources integrated at room temperature with any planar surface could be realized by harnessing the broad spectral tunability,…


Figure 1: Schematics of nanostructured PV architectures studied in this work.  Left to right: QD PbS:ZnO pn-heterojunction (inset shows cartoon of QD passivated by organic ligand on ZnO), ClAlPc:C60 planar heterojunction with ClAlPc molecular structure, DBP:C60 planar heterojunction with DBP molecular structure, and DBP:( DBP/C60):C60 planar mixed heterojunction. All devices are sandwiched between an electron and hole transporting layer such as bathocuproine and molybdenum oxide  and ITO and Au as electrodes.
Recombination Dynamics of Charge Carriers in Nanostructured Solar Cells
  • Nanostructured solar cells attract increasing attention as a promising photovoltaic (PV) technology[1]. Generation of free charge carriers in nanostructured PV…


Figure 2: Cross-sectional SEM of an example metal-organic-metal structure formed with an evaporated Au bottom electrode, self-assembled poly(ethylene glycol) dithiol organic layer, and nanotransfer printed Au top electrode.
Tunneling Nanoelectromechanical Switches Based on Organic Thin Films
  • With the silicon-based electronics reaching physical limits that inhibit continued improvements in device performance, much research has been directed towards…


Figure 1: (a) Electron-hole bilayer TFET structure. (b) Structure with bias and current flow. Red arrows indicate current path. A positively biased top gate attracts electrons while a negatively biased bottom gate attracts holes. Vertical band-to-band tunneling (BTBT) takes place when sufficient voltage is applied across the device so that the electron and hole eigenstates overlap in energy. (c) Energy band diagram across cut shown in (a). A triangular well forms near the top gate for electrons and near the bottom gate for holes. (d) Potential barrier problem solved analytically.
Quantization in Bilayer Tunneling Transistors
  • Tunneling field-effect transistors (TFETs)[1] are promising for low-power applications due to their potential to achieve a subthreshold swing (SS) lower…


Figure 1: (a) Optical image of CVD-grown WSe2 flakes directly grown on SiO2/Si substrate and the back-gated devices on the flake. The triangular shape is consistent with the lattice crystal structure of WSe2 and indicates the high quality of the synthesized sample. (b) Photoluminescence signal mapping of WSe2 flakes. The darker triangle in the center demonstrates thicker islands. (c) Transfer properties of CVD WSe2 back gate devices in linear scale (left) and similog scale (right). Electrons conduct at the high positive back gate voltage region, and holes conduct at the negative bias region. (d) Output performance of WSe2 FET with different back gate bias.
Electronics on MoS2 and Other 2D Semiconductors
  • After enabling much of the modern world for more than 60 years, in the near future electronics will develop in…


Figure 2. SEM image of fin contact test structure. In this device, the Mo contact covers the top as well as the fin sidewalls. The bright lines in the fin cross-section separate the cap, channel, and buffer layers.
Towards a Self-aligned InGaAs Trigate MOSFET
  • Si-based CMOS technology is approaching the limits of its capabilities, and as a result there is extensive research into looking…


Figure 1:  A 30-nm InGaAs nanowire fabricated by our reactive ion etching process.
Towards a Superlattice-source Nanowire FET with Steep Subthreshold Characteristics
  • Achieving a sharp subthreshold swing (S) is crucial to enable the supply voltage scaling that is necessary to reducing power…


Electronic Transport Studies of Thin Film Bi and Bi1-xSbx
  • Currently bulk Bi and BixSb1-x­ have the best known thermoelectric (TE) properties at cryogenic temperatures. These properties can be further…


Figure 1: a) TEM image of highly monodisperse lead sulfide QDs capped with oleic acid ligands. The dots have a mean diameter of 6.3 nm (σ=6.0%) and show self-assembly into a hexagonal closely packed lattice system. An ideal hexagonally close packed lattice is shown in the top inset, with color used to indicate different shells of dots. The bottom inset is high-resolution TEM on a single QD to highlight its crystallinity. b) Center-to-center distance distribution of the main TEM image in Figure 1a, confirming the high degree of ordering in the film. The first major peak indicates an average center-to-center distance between nearest neighbors of 9.6 ± 0.5 nm.
Effect of Morphology in Quantum Dot Electronics
  • Quantum dots (QDs) are exciting materials because their bandgap is dependent on the dot size. The use of QDs allows…


Figure 2. All-dry deposited PEDOT is shown to conformally coat a nanoscale feature. This uniform thickness over sharp features is a substantial improvement over the non-conformal coating properties of spun-coat PEDOT:PSS on features of the same scale.
Applications of Nanoimprinted Structures In Organic Photovoltaics
  • Small-molecule organic photovoltaic cells (OPVs) have the potential to be a low-cost, flexible power conversion solution to many energy problems[1]….


Figure 2: Field ionization of N2: ion current vs. tip-to-gate voltage, VIG, at 10 Torr. Inset shows the experimental setup.
Self-aligned Gated Tip Arrays for Low-voltage, High-pressure Field Ionization of Gases
  • Field ion sources operate based on field ionization (FI) phenomena in which an electron tunnels out of a molecule under…


Figure 1: Time-resolved anti-Stokes Raman imaging schematic. A) A high-energy pulsed laser excites and locally heats the sample with a Gaussian excitation profile. B) After a variable delay time Δt, the Raman probe laser measures the anti-Stokes scattered signal at a known distance from the excitation source. By varying the position and time between the laser pulses, we will map the thermal properties of our samples.
Heat Transport in Nanostructured Materials
  • Thermal management in nanoscale materials dramatically affects the efficiency of novel energy generation technologies, and engineering devices with appropriate heat…


Figure 1: SEM of electrode surface after removal of CNTs, showing a CNT density of approximately 9 x 1010 cm-2.
Improved Carbon Nanotube Ultracapacitor Electrodes for Storage
  • Due to their mechanical, thermal, and electrical properties and their natural ability to grow on a variety of metallic and…


Figure 1: Scanning electron micrographs of fabricated pillar geometries. (a) Electrodeposited Au nanopillars defined by an anodic alumina template. (b) Si nanopillars fabricated using interference lithography and metal-assisted wet etching. (c) Si nanopillars fabricated using e-beam written mask and DRIE. (d) Si micropillars fabricated using optical lithography and DRIE.
Condensation on Micro/Nanostructured Superhydrophobic Surfaces
  • Water condensation on surfaces is a ubiquitous phase-change process that plays a crucial role in nature and across a range…


Figure 1: Artist’s impression of a tip-enhanced microscopy setup.
Spatially Resolved Exciton Dynamics in Quantum Dot Thin Films
  • The diffusion of excitonic energy from within the photosensitive layer of a photovoltaic cell towards the charge separation interface is…


Figure 1: Plot comparing variation of surface area fraction covered by condensed water droplets versus time on surfaces impregnated with Krytox (Sow > 0, solid squares) and BMIm (Sow < 0, open diamonds). The ESEM experiments were conducted under identical conditions (pressure 800 Pa, substrate temperature ~3.6 oC, beam voltage 25 kV, and beam current 1.7 nA). In the analysis, t = 0 s is defined as the first frame in which water drops can be identified
Lubricant-Impregnated Nanotextured Surfaces for Efficient Heat Transfer during Condensation
  • Despite years of advancement in making energy systems more efficient, the predominant mode of condensation seen in large-scale industrial processes…


Figure 2: Effect of ALD encapsulation on time-resolved power conversion efficiency of polymer cells stored in air or in an inert environment.  The cells last
Nano-thin Encapsulation of Photovoltaics via Atomic Layer Deposition
  • Device lifetime is a key figure of merit for solar cells and impacts the levelized energy cost ( $/(kW*hr) )…


Figure 1: (a) Schematic of the droplet jumping mechanism showing two droplets with radii R, prior to (state 1) and immediately after (state 2) coalescence. (b) Side view field emission scanning electron microscopy FESEM image of a nanostructured CuO surface. The sharp, knife-like CuO structures have characteristic heights, h ≈ 1 μm, solid fraction, φ ≈ 0.023, and roughness factor, r ≈ 10. (c) Jumping-droplet superhydrophobic condensation on a nanostructured CuO tube (Inset: magnified view of the jumping phenomena). The tube sample has outer diameter DOD = 6.35 mm, inner diameter, DID = 3.56 mm, and length L = 131 mm.
Scalable Superhydrophobic Copper Oxide Surfaces for Enhanced Heat Transfer
  • Vapor condensation is observed in everyday life and routinely utilized in industry as an effective means of transferring heat. In…


Figure 1: Energetics of Beta and Gamma C2S surfaces. The least energetic surface structures are indicated.
Properties of Polymorphs of Belite
  • Portland cement clinker contains four major phases; alite (C3S) is the most dominant (50-70% by mass) and highly reactive with…


Figure 1: (a) Schematic depiction of oleic-acid-coated lead sulfide QDs (PbsS QDs); the oleic acid ligands are exchanged for 1,3-benzenedithiol (1,3-BDT), 1,2-benzenedithiol (1,2-BDT), or ethanedithiol (EDT). (b) Valence band, Fermi level, and conduction band energies determined from ultraviolet photoelectron spectroscopy and absorption spectroscopy for PbS QDs treated with different ligands. (c) Current-voltage curve of PbS QD/C60 donor-acceptor heterojunction photovoltaics, where the PbS QDs are ligand-exchanged with 1,3-BDT (blue curve) or 1,2-BDT (red curve). The insets depict the expected mode of device operation.
Engineering Energy Level Alignment in Lead Sulfide Quantum- Dot Photovoltaics through Ligand Exchange
  • Solar cells based on lead sulfide colloidal quantum dots (PbS QDs) have made dramatic improvements in efficiency in recent years,…


Figure 1: (a) Top-view SEM image of GaAs nanowire array showing nanowire density and uniformity. (b) 45° tilted nanowire array reveals average height of nanowires as 4.6 μm.  (c) Nanowires have a tapered morphology due to consumption of Ga seed particle.
Self-assisted GaAs Nanowire Growth by MOCVD
  • Nanowires combine the intrinsic properties of semiconductors with low dimensionality, which makes them potential building blocks for optoelectronic applications. GaAs…


Figure 1: Simulated extraction efficiency as a function of the QW placement for m-directional and c-directional axial heterostructures, with the solid line indicating the extraction efficiency for a 
c-directional radial heterostructure with the QW placed at 0.9 the distance from the center to the surface.
Efficiency Comparison of m- and c-directional GaN Nanowire-based LEDs on Si
  • III-nitride nanowire-based light-emitting diodes (LEDs) are promising alternatives to thin-film LEDs for solid-state lighting[1]. Facile strain relaxation in nanowires allows…


Figure 2: Confocal microscopic setup for quantum dot emission measurement.
Tunable Surface Plasmonics on Electric-gated Nanostructures and its Coupling with Quantum Dot Emission
  • The main goal of this work is to introduce functional natural materials into the design of surface plasmonic structures and…


Figure 2: Normalized integrated intensities of the 3.59-eV and 3.35- eV CL luminescence along the length of the nanorod shown in Figure 2(h). The positions of the nanorod coalescence in the n-GaN section and metallurgical junction are indicated. The squares and circles are experimental data and the dashed lines are fits based on an exponential decay model.
Correlation of Doping, Structure and Carrier Dynamics in a Single GaN Nanorod
  • GaN-based nanowires and nanorods are promising materials systems for optoelectronic applications such as high efficiency light emitting diodes[1],[2] or low…


Figure 1: Raman spectroscopy and TEM characterization of bilayer graphene. (a) Two representative Raman spectra taken from suspended bilayer graphene on a SiN TEM grid. The insets show the stacking orientation.  (b) The SAED patterns for (a) and the corresponding intensities profile along the yellow lines. Inset in upper-left corner of (b) is TEM image, which indicates the number of layers.
Rapid Identification of Stacking Orientation in Isotopically Labeled Chemical-vapor Grown Bilayer Graphene by Raman Spectroscopy
  • The growth of large-area bilayer graphene has been of technological importance for graphene electronics. The successful application of graphene bilayers…


Figure 2: Scanning-Electron Micrographs of ZnO NWs grown through EBL-defined PMMA masks with a 1-µm pitch.  a) The growth of the NWs was not perpendicular to the substrate.  (inset) PMMA hole mask before NW growth. b) The growth of the NWs was more perpendicular to the surface than in a) with a reduction of growth-solution molarity and addition of PEI.
Lithographically-defined ZnO Nanowire Growth
  • Photovoltaics (PVs) with inorganic zinc oxide nanowire (ZnO NW) active layers are possible for future generations of technology due to…


Organic Light Emitting Devices on Plastic and Paper Substrates
  • The successful fabrication of optoelectronics on economical, flexible, and lightweight substrates such as plastic and paper could pave the way…


Figure 1: (a) Schematic of graphene supported on a chemically patterned substrate. (b) Schematic of reaction pattern in graphene induced by substrate. (c) Raman map of reaction intensity.
Understanding and Controlling the Substrate Effect on Graphene Electron-transfer Chemistry via Reactivity Imprint Lithography
  • Graphene has exceptional electronic, optical, mechanical, and thermal properties, which provide it with great potential for use in electronic, optoelectronic…


Figure 1. Co-crystals growing on SAMs at increasing magnification.
Concomitant Co-crystallization on Engineered Surfaces
  • A co-crystal is a crystalline material made up of two or more components. In pharmaceutical systems, co-crystallization is frequently used…


Figure 1: Process flow of the single-gated field emission device, simulated using Silvaco.
Silicon Field Emission Devices for X-ray Generation
  • This work focuses on developing an X-ray source using microfabricated silicon field emission devices. In the X-ray source, the electrons…


Figure 2: Aligned-CNT nano-engineered composite macro-scale architectures, nanostitching (a) and fuzzy fiber (b).
Aligned CNT-based Microstructures and Nano-engineered Composite Macrostructures
  • Carbon nanotube (CNT) composites are promising new materials for structural applications thanks to their mechanical and multifunctional properties. We have…


Figure 1: Left: microfluidic device containing a forest of carbon nanotubes through which fluids pass.  Center top: a confocal microscope image of the nanotube forest after the nanotube trees have been individually coated uniformly with molecular layers of polymers containing green fluorescent dye.  Right: Scanning and transmission electron microscope (SEM and TEM) images of the nanotube forest edge.  Center Bottom:  TEM image showing an individual nanotube coated conformally with the polymer layers.
Nanoporous Elements with Layer-by-layer Assembly in MEMS with a Focus on Microfluidic Bioparticle Separation
  • We have integrated ultra-porous (99% porous) elements (nanoporous forests of vertically aligned carbon nanotubes (VACNTs)) in MEMS, showing their use…


Figure 2: Damage inspection of a model bolt-hole composite joint. Voltage (0.16 and 12.3 V) was applied directly through hand-held probes to induce heating.
Preventing Catastrophic Failures: Nano-engineered Multi-physics Materials for Structural Applications
  • Catastrophic structural failures cause many physical and personal losses, with prevention estimated at billions of dollars in savings each year….


Figure 1: TEM micrographs of 10-nm-thick HSQ on 10-nm-thick SiNx membrane substrate, exposed at 200 keV. (A) 10-nm-half-pitch HSQ dot array with 5.1± 0.8 nm feature size. (B) 5-nm-half-pitch HSQ dot array with 5.6 ± 1.2 nm feature size. The dose was (A) 18 and (B) 6 fC/dot. (C) and (D) are typical ~2 nm feature size with 8 nC/cm linear dose.
Resolution Limits of Electron-beam Lithography toward the Atomic Scale
  • Electron-beam lithography (EBL) readily enables the fabrication of sub-10-nm features[1]. However, the resolution limits of this technique at length scales…


Charge Transfer at Junctions of a Single Layer of Graphene and a Metallic Single Walled Carbon Nanotube
  • In this work we fabricate and study junction between a single walled carbon nanotube (SWNT) and a monolayer of graphene…


Figure 2. a) Image of the subwavelength 1D grating fabricated by GIL with the single exposure. During the exposure, the aperture plate moves to the left side of the sample (-x direction) at a constant speed. b) Cross-sectional micrographs of the grating with respect to the position from i to viii regions marked in Figure 2a.
Fabrication of Aperiodic Subwavelength Nanostructures by Grayscale Interference Lithography (GIL)
  • Interference lithography (IL) is one of the most effective and low-cost approaches for large-area nano-patterning and nanostructure fabrication; IL has…


Figure 2: TEM and SAED of silicon nanowires generated from (a) heavily and (b) lightly doped substrates by MCE.
Fabrication of Si Nanowire-Based Capacitors for Power Management
  • Capacitors with high capacitance density (capacitance per footprint area) have potential applications in autonomous microsystems and for power management in…


Figure 1: a) Finite difference time domain (FDTD) simulation of an LRM resonator. b) Measured spectrum of the fabricated LRM filter, showing uncorrupted 4-THz FSR on through and drop ports. c) Temporal response of the thru and drop ports of the LRM filter, excited by 20kHz 0.15V square-wave drive, fit to a 2.6-µs exponential decay and a 1.6-µs rise thermal time constant (shown in red), the insertion loss (IL) of the LRM filter is
L-shaped Resonant Microring Filter with Integrated Thermal Tuner
  • Silicon photonics enables wavelength-division multiplexed (WDM) networks to be efficiently and cost effectively implemented on chip with potential for multi-terabit/s…


Figure 1: a) 3D sketch of the LRM modulator showing size, doping, and metal connections. b) Spur-free single mode operation of the LRM modulator with an FSR of 5.3 THz. c) Spectral response of the LRM modulator with respect to voltage dropped and current passing through the device. d) High speed measured optical eye diagrams at 15-, 20-, 25-, and 30-Gb/s data rates of the LRM modulator, driven by a PRBS data of 2.2Vpp with a -0.6V DC bias. Dynamic insertion loss and extinction ratio are denoted below the eye diagrams.
L-shaped Resonant Microring Modulator
  • On- and off-chip bandwidth and energy scaling are pushing the limits of CMOS and VCSEL technology, which allow only a…


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Adiabatic Resonant Microring Modulators with Integrated Thermal Tuner
  • Wavelength division multiplexed systems can achieve high bandwidth by utilizing many channels on a single fiber as opposed to current…


Figure 1: a) 3D sketch of the microdisk modulator with integrated heater showing size, doping and contacts. b) Measured DC spectral response of the integrated heater inside the microdisk modulator with an applied bias voltage to heater pins. c) High-speed optical eye diagrams at a data rate of 13-Gb/s with an ac-coupled 1.5Vpp drive and 2V applied across heater contacts. The  extinction ratio is 5.8dB and insertion loss is 1.22dB. d) Measured spectral response of the microdisk modulator with applied DC bias voltage to modulator pins from -3V to 0.5V.
Vertical Junction Silicon Microdisk Modulator with Integrated Thermal Tuner
  • Silicon photonics, because it enables wavelength division multiplexed (WDM) systems, will help to minimize the number of fibers required in…


Figure 1: a) Top-view of the 6-µm-diameter microdisk modulator, which utilizes circular inner contacts. b) 2D cross-section showing the doping profile with p-n vertical junction, p+and n+ overlapping regions. c) Spectral response of the microdisk modulator with respect to voltage dropped and current passing through the microdisk modulator. d) High-speed measured optical eye diagrams at 10-, 15-, 20-, and 25-Gb/s data rates of the microdisk modulator, driven by AC coupled 1.2Vpp. The eye diagrams are shown with the true zero (gray line) at each data rate.
Vertical Junction Silicon Microdisk Modulators at 25Gb/s
  • High-performance computing systems require high bandwidth, low power, and scalable optical interconnects to maintain balanced communications in future exascale machines….


Figure 1: Vertical silicon nanowire arrays in channels using metal catalyzed etching.
Silicon Nanowires for Chemical Sensing Systems
  • Silicon nanowires (NWs) have attracted interest for sensing applications due to their high surface-to-volume ratios. When a NW is configured…


CMP Slurry Abrasive Particle Agglomeration Modeling
  • Formerly we presented results of our theoretical agglomeration model for chemical mechanical planarization (CMP) under the primary motivation of understanding…


Figure 1: Fabrication process of the inverted nanocone arrays replicated from nancone arrays.
Inverted Nanocone Arrays with High Aspect Ratio for Mass-producible Multifunctional Films
  • Inspired by natural structures in insect compound eyes, nanocone structures form an effective medium with an axial gradient in the…


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Single- and Multi-wall Carbon Nanotube Growth on Nanoscale Zirconia and Other Oxides as Non-metallic Catalysts
  • This work focuses on the development of non-metallic nanoparticles (NPs) that can catalyze carbon nanofiber (CNF) and nanotube (CNT) growth…


Figure 1: (a) Scanning-electron micrograph of lithographically placed 6-nm-diameter CdSe QDs. The QD clusters were fabricated using PMMA holes with 8-15 nm diameter. (b) Histogram of the number of QDs in each cluster versus the number of clusters, for the sample in (a). We analyzed 54 sites designed for QD clusters. The QDs were counted from the SEM micrographs. Representative SEM images were added to the histogram.
Controlled Placement of Colloidal Quantum Dots in Sub-15-nm Clusters
  • Semiconductor colloidal quantum dots (QDs) are electronically quantized systems with promising applications in optoelectronic devices[1]. A key aspect of such…


Fig. 1. (a) SEM of a SiNx membrane (~ 350-nm thick) with SNSPD on top. (b) Optical micrograph of a membrane-SNSPD that was transferred and aligned to a Si waveguide on a PIC chip. (c) Instrument response function (IRF) of a membrane-SNSPD transferred onto a secondary substrate. The IRF was measured using a mode-locked fiber-coupled laser with sub-ps-pulse-width and 1550-nm wavelength. We measured sub-35-ps timing jitter for detectors with IC > 13 μA.
Membrane-integrated Superconducting Nanowire Single-photon Detectors
  • Superconducting nanowire single-photon detectors (SNSPDs)[1] based on niobium nitride (NbN) nanowires have shown high speed (< 3ns dead time[2] )…


Figure 1: Composition and device performance of typical organic solar cells using graphene anodes. (a) Schematic diagram of the graphene anode OPV architecture: graphene/PEDOT:PEG(PC), 40nm/PEDOT:PSS, 20nm/DBP, 25nm/C60, 40nm/BCP, 8.5nm/Al, 100nm. (b) Cross-sectional TEM image (left) of the complete device described in (a), with an energy dispersive EDS elemental line scan overlaid on a schematic of the device cross-section (right). (c) Flat-band energy level diagram of the completed OPV device. (d) Current density vs. voltage (J-V) characteristics of a representative graphene device (using D-HIL, black) compared with ITO reference cells (red and blue) under simulated AM 1.5G illumination at 100 mW∙cm-2, illustrating comparable performances.
Interface Engineering of Graphene for Universal Applications as Both Anode and Cathode in Organic Photovoltaics
  • The high transparency of graphene[1], together with its good electrical conductivity[2] and mechanical robustness[3], enable its use as transparent electrodes…


Figure 1. Passive phased arrays. (a) A schematic of the large-scale optical phased array. Inset, a scanning electron micrograph (SEM) of a part of the phased array fabricated with the state-of-the-art CMOS technology. (b) Near-field emission of a 64×64 phased array. (c) Simulated and (d) measured far-field interference pattern of a 64×64 phased array to generate an MIT-logo. (e) Simulated and (f) measured far-field interference pattern of a 32×32 phased array to generate multiple beams. The white/red lines separate the interference orders while the green circle depicts the edge of the objective lens.
Large-scale Nanophotonic Phased Array
  • Electromagnetic phased arrays at radio frequencies (RFs) are well known and have enabled applications from communications to radar, broadcasting, and…


Figure 1: SEM images of the most frequently observed patterns formed on the four arrangements (gray scale). Sketched black dots: single posts; red dots: double posts. Blue dotted lines were drawn to clearly show that one out of every nine single posts was replaced with a double post. Colored rectangles: predicted PDMS patterns of each arrangement. Different colors distinguish the predicted patterns of different arrangements.
Rule-based Directed Self-assembly of Circuit-like Block copolymer Patterns
  • Templated self-assembly of block copolymers using topographic templates is attractive because it can generate dense nanoscale patterns over a large…


Figure 1: Effect of wall temperature on the wetting state of a water droplet. (a) Due to roughness-enhanced wettability, a water droplet deposited on a superhydrophilic surface at 120 °C spontaneously spreads into a thin film and wets the surface following surface irregularities with a near zero contact angle. The inset shows the scanning electron micrograph (SEM) image of the microstructured surface (D = 6.6 μm, H = 18.3 μm, and L = 20.0 μm) acquired at 10˚ inclination. (b) A similar size droplet at a higher wall temperature of 160 °C did not wet the same superhydrophilic surface; instead it rests on top of the structured surface forming a Cassie-like droplet. The inset shows a magnified view of the boxed section near the droplet base of a similar experiment indicating that the droplet remained in contact with the pillar tops. The scale bar in the inset represents 100 μm.
Non-Wetting Droplets on Superheated Textured Hydrophilic Surfaces
  • Engineered surfaces have received significant interest for a wide range of applications including microfluidics, drag reduction, self-cleaning, water harvesting, anti-corrosion,…


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Wide-field Multispectral Super-resolution Imaging Using Spin-dependent Fluorescence in Nanodiamonds
  • Recent advances in fluorescence microscopy have enabled spatial resolution below the diffraction limit by localizing multiple temporally or spectrally distinguishable…


Figure 1: Cyclic voltammetry scan at 500mV/s of CNT electrode in NaCl solution. Increasing NaCl concentration, increases electrical capacitance, and decreases ion adsorption and removal from water
Improving Water Desalination Capabilities through the Use of Engineered Nanostructured Materials
  • Manipulation and control of transport at nanometer length scales offers new opportunities to enhance the performance of water desalination systems[1]….


Figure 1: Schematic of absorption and fluorescence enhancement using the J-aggregate excitonic antenna.
Absorption and Fluorescence Enhancement of Single Molecules and Quantum Dots Using an Excitonic Antenna
  • Nature presents us with a fundamental mismatch between the “size” of visible light (~250 nm in free space) and the…