This PDF file contains the front matter associated with SPIE Proceedings Volume 9932, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Prevention of excess heat accumulation within the Li-ion battery cells is a critical design consideration for electronic and photonic device applications. Many existing approaches for heat removal from batteries increase substantially the complexity and overall weight of the battery. Some of us have previously shown a possibility of effective passive thermal management of Li-ion batteries via improvement of thermal conductivity of cathode and anode material¹. In this presentation, we report the results of our investigation of the thermal conductivity of various Li-ion cathodes with incorporated carbon nanotubes and nanodiamonds in different layered structures. The cathodes were synthesized using the filtration method, which can be utilized for synthesis of commercial electrode-active materials. The thermal measurements were conducted with the "laser flash" technique. It has been established that the cathode with the carbon nanotubes-LiCo2 and carbon nanotube layered structure possesses the highest in-plane thermal conductivity of ~ 206 W/mK at room temperature. The cathode containing nanodiamonds on carbon nanotubes structure revealed one of the highest cross-plane thermal conductivity values. The in-plane thermal conductivity is up to two orders-of-magnitude greater than that in conventional cathodes based on amorphous carbon. The obtained results demonstrate a potential of carbon nanotube incorporation in cathode materials for the effective thermal management of Li-ion high-powered density batteries.

Coulomb blockade is observed in suspended graphitic quantum dots designed based on the FET setup with active region being suspended - free from substrate interactions. The fabricated device with relatively thin graphitic layer as an active region exhibits Coulomb blockade features along with the high-T charging effect depending on the driving voltage. The observed features are further discussed in the correlation between the phonon DOS and the anomalies outside of the Coulomb blockade.

The quantification of quantum phase coherence can reveal several properties of charge carriers in systems of given dimensionality, illuminating mechanisms leading to quantum decoherence due to inelastic scattering events, to decoherence mechanisms due to device geometry, and to dephasing due to geometrical phases from applied fields. Examples of several effects are presented. Quantum phase coherence lengths were measured in mesoscopic geometries by quantum transport methods including universal conductance fluctuations, weak-localization, and quantum interferometry. The geometries were fabricated from two-dimensional starting materials. In wires of materials with strong spin-orbit interaction, we show that spin decoherence due to spin-orbit interaction and dephasing due to applied magnetic fields show an electromagnetic duality. We show that dephasing due to applied magnetic fields can be expressed in terms of a magnetic length quantifying time-reversal symmetry breaking. In wires, the main orbital quantum decoherence mechanism related to the wire length appears as environmental coupling decoherence, with longer wires showing asymptotically longer phase coherence lengths. For mesoscopic stadia, the geometry plays an additional role, inducing stadium-wire coupling decoherence.

Radial deformation phenomena of carbon nanotubes (CNTs) are attracting increased attention because even minimal changes of the CNT's cross section can result in significant changes of their electronic and optical properties. It is therefore important to have the ability to sensitively probe and characterize this radial deformation. High pressure Raman spectroscopy offers a general and powerful method to study such effects in SWNTs. In this experimental work, we focus in particular on one theoretically predicted Raman vibrational mode, the so-called "Squash Mode" (SM), named after its vibrational mode pattern, which has an E_2g symmetry representation and exists at shifts below the radial breathing mode (RBM) region. The Squash mode was predicted to be more sensitive to environmental changes than the RBM.

Here we report on a detailed, experimental detection of SMs of aligned SWNT arrays with peaks as close as 18 cm^-1 to the laser excitation energy. Furthermore, we investigate how the SM of aligned CNT arrays reacts when exposed to a high pressure environment of up to 9 GPa. The results confirm the theoretical predictions regarding the angular and polarization dependent variations of the SM's intensity with respect to their excitation. Furthermore, clear Raman upshifts of SM under pressures of up to 9 GPa are presented. The relative changes of these upshifts, and hence the sensitivity, are much higher than that of RBMs because of larger radial displacement of some of the participating carbon atoms during the SM vibration.

These novel ultra-sensitive Raman SM shifts of SWNTs provide enhanced sensitivity and demonstrate new opportunities for nano-optical sensors applications.

Porous fibrous membranes having multiple scales geometries and tailored properties have become attractive microfabrication materials in recent years. Due to the feasibility of incorporating graphene in electrospun nanofibres and the growing interest on these nanomaterials, the present paper focuses on the electrospinning of Poly (ε-Caprolactone) (PCL) solutions in the presence of different amounts of Graphene platelets. Electrospinning is a process whereby ultrafine fibers are formed in a high-voltage electrostatic field. The morphological appearance, fiber diameter, and structure of PCL nanofibers produced by the electrospinning process were studied in the presence of different concentration of graphene. Moreover, the effect of a successful incorporation of graphene nanosheets into PCL polymer nanofibers was analyzed. Scanning electron microscope micrographs of the electrospun fibers showed that the average fiber diameter increases in the presence of graphene. Furthermore, the intrinsic properties developed due to the interactions of graphene and PCL improved the mechanical properties of the nanofibers. The results reveal the effect of various graphene concentrations on PCL and the strong interfacial interactions between the graphene platelets phase and the polymer matrix. The functional complexity of the electrospun fibers provides significant advantages over other techniques and shows the promise of these fibers for many applications including air/water filters, sensors, organic solar cells, smart textiles, biocompatible scaffolds for tissue engineering and load-bearing applications. Optimizing deposition efficiency, however, is a necessary milestone for the widespread use of this technique.

Two-dimensional (2D) materials beyond graphene such as transition metal dichalcogenides (TMDs) have unique mechanical, optical and electronic properties with promising applications in flexible devices, catalysis and sensing. Optical imaging of TMDs using photoluminescence and Raman spectroscopy can reveal the effects of structure, strain, doping, defects, edge states, grain boundaries and surface functionalization. However, Raman signals are inherently weak and so far have been limited in spatial resolution in TMDs to a few hundred nanometres which is much larger than the intrinsic scale of these effects. Here we overcome the diffraction limit by using resonant tip-enhanced Raman scattering (TERS) of few-layer MoS2, and obtain nanoscale optical images with ~ 20 nm spatial resolution. This becomes possible due to electric field enhancement in an optimized subnanometre-gap resonant tip-substrate configuration. We investigate the limits of signal enhancement by varying the tip-sample gap with sub-Angstrom precision and observe a quantum quenching behavior, as well as a Schottky-Ohmic transition, for subnanometre gaps, which enable surface mapping based on this new contrast mechanism. This quantum regime of plasmonic gap-mode enhancement with a few nanometre thick MoS2 junction may be used for designing new quantum optoelectronic devices and sensors.

Two-dimensional transition metal dichalcogenides (TMDCs) show a great potential for optoelectronic applications due to their unique properties. However, the control of their emission through coupling to nanoantennas remains largely unexplored. Importantly, antenna-TMDCs coupling promised to be an effective way for PL control due to the high Purcell enhancement such plasmonic nanostructures can offer. MoSe2, a member of the TMDCs family, is an appealing candidate for coupling to gold plasmonic nanostructures due to its smaller bandgap and higher electron mobility in comparison to the readily used MoS2. Moreover, the PL of MoSe2 occurs in the near-infrared spectral range, where the emissive properties do not suffer from the enhanced dissipation in the gold due to interband transitions. Here we study the interaction between monolayer MoSe2 and plasmonic dipolar antennas demonstrating efficient control of the PL from the TMDC layer. In our experiments, we transfer an exfoliated monolayer MoSe2 onto an array of rectangular gold nanoantenna whose plasmonic resonances overlap with the PL emission of the material. By varying a thickness of the spacer between the MoSe2 layer and the nanoantenna, we demonstrate tuneable PL from threefold enhancement (sample with spacer) to twice quenching (sample without spacer). Furthermore, the observed PL from the TMDC-antenna system demonstrates polarization-dependent properties, thus offering the possibility of polarization-based PL control. Our experimental results are supported by numerical simulations. To the best of our knowledge, this is the first study of Au-MoSe2 plasmonic hybrid structures realizing flexible PL manipulation, which is promising for future optoelectronic applications.

We analyze the propagation of electromagnetic fields through tight-binding arrays of coupled photonic waveguides as a symmetry problem in the case of invariant properties of the propagation distance. We consider the Heisenberg-Weyl group and the photonic lattices with that underlying symmetry. Based on this, dispersion relations, impulse functions and normal states can be constructed from the point of view of Gilmore-Perelomov coherent state approach and different classes of propagation invariant input can be constructed.

We propose an attosecond strong optical field interferometry in graphene which reveals the chirality of graphene without employing a magnetic field. A circularly polarized optical pulse with strong amplitude and femtosecond time scale causes the electron to circle in the reciprocal space through which it accumulates the dynamic phase along the closed trajectory as well as the nontrivial geometric phase known as Berry’s phase. The resulting interference fringes carry rich information about the electronic spectra and interband dynamics in graphene near the Dirac points. Our findings hold promises for the attosecond control and measurement of electron dynamics in condensed matters as well as understanding the topological nature of the two-dimensional Dirac materials.

Use of diamond as a semiconductor material suffers from the high activation energy of all known impurity dopants (0.37 eV for Boron, 0.6 eV for Phosphorous). To achieve the simultaneous carrier concentration and mobility desired for devices operating at room temperature, growth of a nanometric thick ‘delta’ layer doped to above the metal insulator transition adjacent to high mobility intrinsic material can provide a 2D high mobility conduction layer. Critical to obtaining the enhanced mobility of the carriers in the layer next to the ‘delta’ doped layer is the abruptness of the doping interface. Single and multiple nanometer thick epitaxial layers of heavily boron ‘delta’ doped diamond have been grown on high quality, intrinsic lab grown diamond single crystals. These layers were grown in a custom microwave plasma activated chemical vapor deposition reactor based on a rapid reactant switching technique. Characterization of the ‘delta’ layers by various analytical techniques will be presented. Electrical measurements demonstrating enhanced hole mobility (100 to 800 cm2/V sec) as well as other electrical characterizations will be presented.

Owing to its superb thermal and electrical attributes, as well as electrochemical stability, carbon is emerging as an attractive material for fabrication of many bioelectrochemical devices such as biosensors and biofuel cells. However, carbon’s inert nature makes it difficult to functionalize with biocatalysts; often requiring harsh chemical treatment, such as nitric acid oxidation, to attach reactive amines and carboxylic acids to its surface. Recent studies, however, points toward a self-assembly approach for fabricating well organized layers of carbon loaded with arrays of metallic nanoparticles patterned by block-copolymers (BCP) templates. Herein, we demonstrate an effective method for developing carbon nanofibers meshes embedded with metal nanoparticles, by incorporating a BCP self-assembly approach into our C-MEMS fabrication technique. The main phase of this hybrid method includes electrospinning metal salt-loaded BCP into nanofiber meshes, and subsequently reducing the metal salts into metal nanoparticles prior to pyrolysis. This cost-effective process will pave the way for fabricating scalable advanced 3-D carbon electrodes that can be applied to biosensors and biofuel cells devices.

The increase in the temperature of photovoltaic (PV) solar cells affects negatively their power conversion efficiency and decreases their lifetime. The negative effects are particularly pronounced in concentrator solar cells. Therefore, it is crucial to limit the PV cell temperature by effectively removing the excess heat. Conventional thermal phase change materials (PCMs) and thermal interface materials (TIMs) do not possess the thermal conductivity values sufficient for thermal management of the next generation of PV cells. In this paper, we report the results of investigation of the increased efficiency of PV cells with the use of graphene-enhanced TIMs. Graphene reveals the highest values of the intrinsic thermal conductivity. It was also shown that the thermal conductivity of composites can be increased via utilization of graphene fillers. We prepared TIMs with up to 6% of graphene designed specifically for PV cell application. The solar cells were tested using the solar simulation module. It was found that the drop in the output voltage of the solar panel under two-sun concentrated illumination can be reduced from 19% to 6% when grapheneenhanced TIMs are used. The proposed method can recover up to 75% of the power loss in solar cells.

Increased depletion of fossil fuels along with global warming and climate change made the society to think about alternate green and sustainable energy sources and better energy storage devices. Extensive research has been performed on the development of solar cells, fuel cells, Lithium- ion battery and supercapacitors to combat the green house effect and its consequences, and to meet the increased energy crisis. Supercapacitors, also known as electrochemical capacitors are gained a great attention because of their pulse power supply, long cycle life (>100,000), simple principle and high dynamic of charge propagation. Its greater power density than lithium- ion battery and much larger energy density than conventional capacitors brought super capacitors to a promising energy storage device to meet the increased energy demands. Here we demonstrate supercapacitor electrode materials with graphene oxide (electric double layer capacitor) and α-MnO₂ nanomaterial (pseudo-capacitor), as well as composite of these materials, which means that the bulk of the material undergoes a fast redox reaction to provide the capacitive response and they exhibit superior specific energies in addition to the carbon-based supercapacitors (double-layer capacitors). A simple soft chemical route is utilized to synthesize graphene oxide, α-MnO₂ and graphene oxide-MnO₂ composite. The phase and the structure of the synthesized materials are studied using X-ray diffractometry (XRD). The functional group and the presence of impurities are understood from Fourier transform infrared (FTIR) spectra. The capacitive properties of the graphene oxide, graphene oxide - MnO₂ nanocomposite and α-MnO₂ are tested with the help of cyclic voltammetry (CV) and galvanostatic charge – discharge techniques using 1 M Na₂SO₄ in aqueous solution as electrolyte. It was found that graphene oxide - MnO₂ nanocomposite shows better electrochemical behaviour compared to individual graphene oxide and α-MnO₂ nanomaterial.

Recently, extraordinary physical properties of two-dimensional transition metal dichalcogenides (TMDs) have attracted great attention for various device applications, including photodetectors, field effect transistors, and chemical sensors. There have been intensive research efforts to grow high-quality and large area TMD thin films, and chemical vapor deposition (CVD) techniques enable scalable growth of layered MoS2 films. We investigated the roles of Au nanoparticles (NPs) on the transport and photoresponse of the CVD-grown MoS2 thin films. The Au NPs increased conductivity and enabled fast photoresponse of MoS2 thin films. These results showed that decoration of metal NPs were useful means to tailor the physical properties of CVD-grown MoS2 thin films. To clarify the roles of the metal particles, we compared the transport characteristics of MoS2 thin films with and without the Au NPs in different gas ambient conditions (N2, O2, and H2/N2). The ambient-dependence of the MoS2 thin films allowed us to discuss possible scenarios to explain our results based on considerations of band bending near the Au NPs, gas adsorption/desorption and subsequent charge transfer, and charge scattering/trapping by defect states.

The peculiar electronic structure of graphene results in a large optoelectronic response that holds great potential for technology. For example, this material exhibits a nearly constant absorption ~2.3% over a broad spectral range [1], which can be electrically modulated in the mid-IR by injecting attainable densities of charge carriers. When doped, graphene can sustain plasmons that radically modify its optical response, enabling complete optical absorption for suitably designed patterns [2]. Graphene nanoribbons constitute one of the simplest geometrical patterns that one can produce. They have been extensively studied and their plasmons accurately explained with simple models [3]. When heated to a large electronic temperature, graphene behaves nearly as if is was highly doped, also giving rise to plasmon modes [4]. In this work, we study the possibility of using ultrashort light pulses together with the natural electronic relaxation mechanisms in graphene nanoribbons as a way to tune their optical response. We first discuss the optically induced plasmons of individual nanoribbons when illuminated with ultrashort pulses and then analyze the evolution of the plasmon frequency as a function of the delay between pump and probe. We study the redshift of these plasmons with increasing delay due to electron relaxation. We also investigate the optical response of the ribbon exposed to a train of optical pulses. We further discuss ribbon arrays illuminated from the substrate under total internal reflection conditions, for which we predict complete absorption for a suitable choice of geometrical and illumination parameters. References [1] F. H. L. Koppens, D. E. Chang, and F. J. García de Abajo, Nano Letters 11, 3370-3377 (2011) [2] S. Thongrattanasiri, F. H. L. Koppens, and F. J. García de Abajo, Phys. Rev. Lett. 108, 047401 (2012) [3] I. Silveiro, J. M. Plaza Ortega, and F. J. García de Abajo, Light: Science and Applications 4, e241 (2015) [4] F. J. García de Abajo, ACS Photon. 1, 135 (2014).

Optical metasurfaces are thin-layer subwavelength patterned structures that interact strongly with light. Metasurfaces have become the subject of several rapidly growing areas of research, being a logical extension of the field of metamaterials towards their practical applications. Metasurfaces demonstrate many useful properties of metadevices with engineered resonant electric and magnetic optical responses combined with low losses of thin-layer structures. In this talk, we introduce the basic concepts of this rapidly growing research field and review the most interesting properties of photonic metasurfaces, demonstrating their useful functionalities such as frequency selectivity, wavefront shaping, tunability and polarization control. More specifically, we demonstrate that all-dielectric metasurfaces provide a powerful platform for highly efficient flat optical metadevices, owing to their strong electric and magnetic dipolar response accompanied with negligible losses at near-infrared frequencies. In particular, we experimentally demonstrate several different types of planar metadevices, as well as realize dynamic tuning of electric and magnetic resonances in the telecom spectral range. Strongly different tuning rates are observed for the electric and the magnetic response, which allows for dynamically adjusting the spectral mode separation. Furthermore, we study the influence of the anisotropic (temperature-dependent) dielectric environment provided by the liquid crystal and demonstrate that the phase transition of the liquid crystal from nematic to isotropic phase can break the symmetry of the optical metasurface response. In addition, we discuss our studies of the interaction between monolayer MoSe2 and plasmonic dipolar antennas, and demonstrate manipulation of the photoluminescence intensity from quenching to enhancement and its strong polarization dependence.

Due to its remarkable properties, graphene-based devices are particularly promising for optoelectronic applications. Thanks to its compatibility with standard silicon technology, graphene could compete III-V compounds for the development of low cost and high-frequency optoelectronic devices. We present a new optoelectronic device that consists in a coplanar waveguide integrating a commercially-available CVD graphene active channel. With this structure, we demonstrate high-frequency (30 GHz) broadband optoelectronic mixing in graphene, by measuring the response of the device to an optical intensity-modulated excitation and an electrical excitation at the same time. These features are particularly promising for RADAR and LIDAR applications, as well as for low-cost high-speed communication systems.

The particular Graphene-Germanium-Graphene photodetector (GSG PD) is investigated in this research. Germanium has good absorption coefficient in near infrared such as 850 nm, 1310 nm and 1550 nm which are commonly used in optics communication. Generally, the metal electrode was utilized for photodetector and there were lots of light being loss. In recent years, graphene is found to be a good conductive film. It is a two-dimensional monolayer of sp2-bonded carbon atoms. In cases where synthesized by chemical vapor deposition (CVD), graphene is especially a promising candidate for transparent conductive films (TCFs) due to its exceptional electrical conductivity and high optical transmittance which is almost transparent in the wide wavelength range, especially including near infrared. Therefore, the higher photo current and responsivity of the device can be achieved. In this investigation, interdigitated graphene electrodes are used on the devices with the purposes of a relatively easy process for high-speed devices and a comparable process for the integrated circuit. We used the n-type Germanium as the substrates for the absorption of photodetector and different layers of graphene as the interdigitated electrodes. The interdigitated graphene electrode is prepared by transferred the graphene which is grown by CVD on the substrate first and then pattern by O2 plasma. The most direct method of measuring the photo current is to be incident a laser source by fiber and give a DC bias then using KEITHLEY 2400 Source Meter to measure current from photodetectors. As the result of that, we can calculate the responsivity by formula.

In this paper we considered in details of the energy exchanges that would take place when concentrated solar energy is focused normally onto a thermionic emitter of area equal to the area of focus with solar energy being incident parallel to the axis of the parabolic mirror. We then, using a simplified version of the equations, compute the power output from the thermionic energy converter with emitters of graphene on silicon carbide, assuming that with the advent of new work function engineering technology the work function of graphene can be modulated from 4.5 eV to 1.5 eV and also with pure monolayer graphene for which a new thermionic emission equation has been discovered by the authors. Our theoretical research shows that graphene being a high temperature material, it is quite possible to practically realize a solar thermionic energy converter with good conversion efficiency using a graphene-on-silicon carbide emitter.