This PDF file contains the front matter associated with SPIE Proceedings Volume 9168, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

We present a practical and robust concept to bypass the typical trade-off between optical transparency and electrical conductivity of transparent conducting electrodes. A transparent conducting electrode serves to transmit photons and conduct electrons, and the frequencies of the corresponding optical and dc electric fields differ by at least 12 orders of magnitude. Therefore, we could engineer the optical electric field to influence the optical property, which is not intrinsic, of the transparent electrode without sacrificing its electrical performance. For a given light power input, the optical impedance transformer reduces the loss in a transparent electrode by raising the refractive index of its surrounding medium. The concept of optical impedance transformer can be realized by nanocone arrays, and we use it to design nanophotonic structures that provide broadband and omnidirectional reduction of optical loss in an ultrathin graphene electrode. In addition, the concept applies to thicker or nanostructured transparent electrodes. The results are verified against first-principles full-field electromagnetic simulations.

Carbon-nanotubes (CNT) are fascinating compounds, exhibiting exceptional electrical, thermal conductivity, mechanical strength, and nonlinear optical (NLO) properties. Their unique structures involve large π-π* electronic clouds. The energy level schemes thus created allow many electronic transitions between the ground and the excited states. The present work involves CNT-doped hybrid organic-inorganic glass composites prepared by a Fast-sol-gel method. Such composite glasses solidify without shrinkage or crack formation, and exhibit promising properties as optical devices. In this work we have studied nonlinear optical and electrical conductivity properties. The CNT composite glasses exhibited enhanced absorption at 532 nm, and saturable absorption at 1064 nm. The enhanced absorption at 532 was attributed to 2-photon absorption; saturable absorption was attributed to depletion of the absorbing ground-state, and was analyzed using the modified Frantz-Nodvik equation. Absorption cross-sections were extracted for the saturable absorption phenomenon. Such CNT composites glasses may be used as "optical limiting" filters in lasers near 532 nm, or as saturable absorbing filters for passive laser Q-switching near 1064 nm. The CNT composites electrical conductivity was studied as a function of the CNT concentration and modeled by a percolation theory. The maximal measured conductivity was σ ≈10^-3 (Ωcm)^-1 for the CNT composites, representing a conductivity increase of at least 12 orders of magnitude compared to that of pure silica. A quite low percolation threshold was obtained, φ_c = 0.22 wt.% CNT. Electrostatic Force Microscopy (EFM) and Conductive mode Atomic Force Microscopy (C-AFM) studies revealed that the conductivity occurs at the micro-level among the CNTs dispersed in the matrix.

We report a highly sensitive substrate for surface enhanced Raman spectroscopy (SERS) enabled by arrays of metal (gold and silver) nanowires on the template of vertically aligned (VA-) carbon nanotubes (CNTs) coated with a high-k dielectric hafnia (HfO₂) layer as a potential barrier. Femtomolar detection of 1,2 bis-(4-pyridyl)-ethylene (BPE) is demonstrated with this non-resonant substrate. Comparison of SERS performance with and without the hafnia potential barrier establishes the critical contribution of this dielectric nano spacer to the large sensitivity. This behavior is attributed to the relief of electric charge leakage from metal to the CNT template in the presence of the virtual energy potential barrier. The VA-CNT substrate, when covered by dielectric barriers, can be a great template for a practical and reproducible SERS substrate.

Graphene, an atomically thin sheet of hexagonally oriented carbon, is a zero band gap semi-metal that exhibits extraordinary electronic and optical behavior. Hexagonal boron nitride, which shares a similar structure to that of graphene, is an insulator that does not absorb any light in the visible spectrum. By combining graphene and boron nitride into ultrathin vertical stacks, we fabricated new optoelectronic devices that demonstrate highly sensitive optical response, yet are only several nanometers thick. In this talk, I will discuss how stacking these atomically thin materials allows us to explore new types of optoelectronic devices that reveal a novel hot carrier transport regime, which may lead to more efficient energy harvesting technologies.

We propose a facile approach to fabricate graphene nano-objects (GNOs) using interference lithography (IL) and direct self-assembly of nanoparticles. Uniformly spaced parallel photoresist (PR) lines and periodic hole arrays are proposed as an etch mask for producing graphene nanoribbons (GNRs), and graphene nanomesh (GNM), respectively. In a different experiment, the PR line arrays are transferred to uniform oxide channels, and silica nanoparticle dispersions with an average size of 10 nm are spun on the patterned surface, leaving a monolayer uniform nanoparticle assembly on the graphene. Following the particle deposition, the graphene is removed in the narrow spacing between the particles, using the O2 plasma etch, leaving ordered graphene quantum dot (GQD) arrays. The IL technique and etch process enables tuning the GNOs dimensions.

We report formation of an optical cavity and observation of Fabry-Perot resonance in GaAs nanowires and nanosheets grown by metal organic chemical vapor deposition (MOCVD) with selective area growth (SAG). These nanostructures are grown along the (111)B direction. The formation of an optical cavity in the nanowires and nanosheets are fundamentally different from each other. In nanowires the optical cavity is formed along the length of the nanowire with ends of the nanowire behaving as two parallel mirrors. In nanosheets, however, the three non-parallel edges of the GaAs nanosheets are involved in trapping of the light through total internal reflection, thus forming a 2D cavity. We show that through surface passivation and local field enhancement, both the photoluminescence intensity and hence Fabry-Perot peak intensity increases significantly. Transferring the GaAs nanowires and nanosheets to the gold substrate (instead of Si/SiO2 substrate) leads to substantial enhancement in the photoluminescence intensity by 5X (for nanowires) and 3.7X (for nanosheets) to infinite enhancement of the FP peaks intensities. In order to reduce the non-radiative recombination in these nanowires the surface states in the nanowires can be passivated by either an ionic liquid (EMIM-TFSI) or an AlGaAs surface layer. Both passivations methods lead to an enhancement of the optical response by up to 12X.

In this paper, for the first time, we derive the appropriate form of Maxwell-Dirac equations for simulation of the coupling transport of electromagnetic fields and carriers in graphene nanostructures, and propose a time splitting spectral method for the numerical solution of this multiphysics problem.In this time splitting spectral method, we split each time step into three substeps. In each substep, we split the linear and nonlinear parts of the complicated nonlinear coupling Maxwell-Dirac system, then iteratively solving each simple part by linearizing the nonlinear part. The time derivatives are discretized by finite difference method with second order accuracy schemes. The spatial differential operators are approximated by spectral differentiation matrices. The proposed numerical method is validated by numerical examples that simulate the propagation of electromagnetic wave in graphene nanowaveguides.

We demonstrate a new regime of intrinsic exciton photophysics in SWCNTs with narrow spectral linewidth down to 200 μeV and prolonged spontaneous emission times up to T1=18 ns, about two orders of magnitude better than prior measurements and in agreement with values(10-100ns) hypothesized by theorists about a decade ago. Furthermore, we establish for the first time exciton decoherence times of individual nanotubes in the time domain and find fourfold prolonged values up to T2=2.1 ps compared with ensemble measurements. These first observations motivate new discussions about the magnitude of the intrinsic dephasing mechanism while the prolonged exciton dynamics is promising for applications.

Three dimensional pillared graphene nanostructures were grown on metal substrates through a one-step chemical vapor deposition (CVD) by introducing a mixture precursor gases (H₂, C₂H₄). We further explored sputtering evaporation system to uniformly deposited a layer of amorphous silicon on the as grown 3D carbon nanostructure. The surface morphologies of the carbon-silicon nanocomposites were investigated by scanning electron microscopy (SEM). Cyclic voltammetry and charge-discharge are conducted to determine the performance of the 3D hybrid carbon-silicon nanostructure for lithium ion battery anode.

Isolated individual carbon nanotubes (CNTs) have shown exceptional thermal conductivity along their axis, but have poor thermal transfer between adjacent CNTs. Thick bundles of aligned CNTs have been used as heat pipes, but the thermal input and output areas are the same, providing no heat spreading effect. Energetic argon ion beams are used to join, or cross-link overlapping CNTs in a thick film to form an interpenetrating network with an isotropic thermal conductivity of 2150 W/m-K. Such thick films may be used as heat spreaders to enlarge the thermal footprint of various electronic and semiconductor devices, laser diodes and CPU chips, for example, to enhance cooling.

In addressing the use of noble metal-dressed carbon nanotubes (CNTs) as a substrate for surface enhanced Raman scattering (SERS) we re-direct attention from interactions at the outer interface with deposited molecular species to interactions at the inner (silver-CNT) interface and the extraction of enhanced D- and G-band signals from the CNTs themselves. This offers a means for reliable, Raman-based characterization of vertically aligned CNTs at a sensitivity improved by over an order magnitude; obtaining data from individual CNTs is readily achievable. Experimental data will be interpreted with the assistance of electromagnetic modelling of the optical response.

We report the results of an experimental study that compares the performance of graphene and boron nitride flakes as fillers in the thermal interface materials. The thickness of both fillers varied from a single atomic plane to about a hundred. The measurements have been conducted using a standard TIM tester. Our results show that the addition of a small fraction of graphene (f=4 wt%) to a commercial thermal interface material increases the resulting apparent thermal conductivity substantially stronger than the addition of boron nitride. The obtained data suggest that graphene and fewlayer graphene flakes couple better to the matrix materials than the boron nitride fillers. A combination of both fillers can be used to increase the thermal conductivity while controlling the electrical conduction.

This study was to separate the semiconducting and the metallic types of single-wall carbon nanotubes (SWNTs) by electrophoresis with the different dispersants that are deoxyribonucleic acid (DNA), Triton X-100 and sodium dodecyl sulfate (SDS), respectively. The dispersants modify the surface of SWNTs and disperse in the de-ionized water. and used electric power supply 100V to electrophoresis. However, the different dispersants such as DNA, Triton X-100 and SDS coated on SWNTs have different property of electronic field. Hence, in the same power of electrophoresis was applied to separate out s-SWNT and m-SWNT from the raw-SWNT. In addition, the DNA base pair and quantitative can be determine by electrophoresis with standard mark. The electrophoresis has features that low sample need, low energy required and efficiently for this fabrication. The results of Raman spectrum could verify the separation efficiency and determine the electrical of the samples with the radial breathing mode (RBM, 100-400cm^-1) of SWNT. After the dispersion process with DNA, a new peak (~1450 cm^-1) has been observed between D-band (~1350cm^-1) and G-band (~1550cm^-1) that also can identify s-SWNT and m-SWNT.