This PDF file contains the front matter associated with SPIE Proceedings Volume 9552, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

Graphene’s exceptional properties make it attractive for technological applications in many areas, including high-speed electronics. The establishment of processes for producing high quality, large-scale graphene is necessary for such applications. Large area growth of epitaxial graphene on the Si-face of hexagonal SiC (0001) wafers exhibits manageable growth kinetics, and most importantly, its azimuthal orientation is fixed, as it is determined by the structure of the single crystal substrate. Therefore, this is a viable method for producing graphene with uniform coverage and structural coherence at wafer-scale.[1],[2] Semi-insulating SiC is a good substrate for graphene RF transistors, however, its cost is so high that potentially only niche applications of graphene on SiC (e.g. defense or space related) can be viable. Furthermore, to enable hybrid electronics, where standard circuits built on Si perform digital logic functions while graphene that does not exhibit a band gap is used for ultrafast analog devices, we would need to transfer epitaxial graphene onto Si wafers. To address these issues, we have developed a method in which a graphene film grown on a 4” SiC wafer is exfoliated via the stress induced by an overgrown Ni film and transferred to other substrates, resulting in a wafer-scale monolayer of graphene that is continuous and has a single azimuthal orientation.[3] This growth and transfer process can be repeated on the same SiC wafer hundreds to thousands of times, dramatically reducing the cost per wafer-sized graphene layer. The characterization of the transferred films shows that they are of quality similar to the pristine films on SiC. Capitalizing on this new method for single crystal epitaxial graphene transfer, we have initiated a project to produce bilayers of graphene with deterministically controlled twist angles. The inspiration for this experimental work is recent theoretical work by Maroudas and coworkers4 that predicts the opening of substantial band gaps at specific twist angles in bilayer graphene. We will report our methods for producing twisted bilayers with controlled twist angle, their characterization and device results. [1] C. Dimitrakopoulos, Y.-M. Lin, A. Grill, D. B. Farmer, M. Freitag, Y. Sun, S.-J. Han, Z. Chen, K. A. Jenkins, Y. Zhu, Z. Liu, T. J. McArdle, J. A. Ott, R. Wisnieff, Ph. Avouris J. Vac. Sci. Technol. B 28, 985-992, (2010). [2] Y.-M. Lin, C. Dimitrakopoulos, K. A. Jenkins, D. B. Farmer, H.-Y. Chiu, Ph. Avouris Science 327, 662 (2010). [3] J. Kim, H. Park, J. B. Hannon, S. W. Bedell, K. Fogel, D. K. Sadana, C. Dimitrakopoulos Science 342, 833-836 (2013). [4] A. R. Muniz, D. Maroudas Phys. Rev. B 86, 075404 (2012)

Interferometrically defined 3D photoresist scaffolds are formed through a series of three successive two-beam interference exposures, a post exposure bake and development. Heating the resist scaffold in a reducing atmosphere to > 1000 °C, results in the conversion of the resist structure into a carbon scaffold through pyrolysis, resulting in a 3D sp₃- bonded glassy carbon scaffold which maintains the same in-plane morphology as the resist despite significant shrinkage. The carbon scaffolds are readily modified using a variety of deposition methods such as electrochemical, sputtering and CVD/ALD. Remarkably, sputtering metal into scaffolds with ~ 5 unit cells tall results in conformal coating of the scaffold with the metal. When the metal is a transition metal such as nickel, the scaffold can be re-annealed, during which time the carbon diffuses through the nickel, emerging on the exterior of the nickel as sp2-bonded carbon, termed 3D graphene. This paper details the fabrication, characterization and some potential applications for these structures.

Vertical and planar III-V nanowire growth on 2D van der Waals sheets by MOCVD will be presented, along with axial and radial p-n junction based solar cells.

Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only in the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. With the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.

The single-atom thickness of monolayer graphene makes it an ideal candidate for DNA sequencing as it can scan molecules passing through a nanopore at high resolution. Additionally, unlike most insulating membranes, graphene is electrically active, and this property can be exploited to control and electronically sense biomolecules. We show that the shape of the edge as well as the shape and position of the nanopore can strongly affect the electronic conductance through a lateral constriction in a graphene nanoribbon as well as its sensitivity to external charges. In this context the geometry of the graphene membrane can be tuned to detect the rotational and positional conformation of a charge distribution inside the nanopore. We show that a quantum point contact (QPC) geometry is suitable for the electrically-active graphene layer and propose a viable design for a graphene-based DNA sequencing device.

In this study, Cu2ZnSn(S,Se)4 (CZTSSe) thin films are subjected to long, low-temperature annealing treatments which have been suggested to bring the material through an “order/disorder” transition. The samples are then characterized by intensity-dependence photoluminescence measurements at low temperature. We observe that annealing the films at 150°C for 1 day causes a shift in the sub-band gap (Eg) states towards higher photon energies. One week of annealing appears to result in a similar electronic structure as 1 day of annealing, and therefore the measurements performed after 1 day roughly represents the equilibrium (kinetically-limited) defect structure for this temperature. Importantly, all samples measured in this study display strong recombination through deep states up to ~330 meV below the band gap. Therefore, while some improvements are observed to occur after long low-temperature annealing, we find that this approach does not fully remedy the band tailing states found to limit the Voc in CZTSSe thin film photovoltaics.

The high optical transmittance, electrical conductivity, flexibility and chemical stability of graphene have triggered great interest in its application as a transparent conducting electrode material and as a potential replacement for indium doped tin oxide. However, currently available large scale production methods such as chemical vapor deposition produce polycrystalline graphene, and require additional transfer process which further introduces defects and impurities resulting in a significant increase in its sheet resistance. Doping of graphene with foreign atoms has been a popular route for reducing its sheet resistance which typically comes at a significant loss in optical transmission. Herein, we report the successful bromine doping of graphene resulting in air-stable transparent conducting electrodes with up to 80% reduction of sheet resistance reaching ~180 Ω/ at the cost of 2-3% loss of optical transmission in case of few layer graphene and 0.8% in case of single layer graphene. The remarkably low tradeoff in optical transparency leads to the highest enhancements in figure of merit reported thus far. Furthermore, our results show a controlled increase in the workfunction up to 0.3 eV with the bromine content. These results should help pave the way for further development of graphene as potentially a highly transparent substitute to other transparent conducting electrodes in optoelectronic devices.

Thermal instability is an important concern for practical use of high-current field emitters in display, X-ray generation, Hall thruster, and microplasma generation. Carbon nanotubes (CNTs) and their bundles have high thermal conductivity and offers great promise in this aspect. A wide-range of experiments has recently been performed with CNT-based emitters containing single or a bundle of nanotubes. Analysis of these experiments is executed using the classical Fowler-Nordheim (FN) equation and the heat equation with no self-consistency. The space-charge effect – one of the most important aspect of high-current field emission – is often ignored in these theoretical analyses. In this work, we use a numerical framework to study thermal instability in the CNT-based emitters by solving electrostatics, space-charge effect, quantum-mechanical tunneling (with FN equation as the limiting case), thermionic emission and heat flow in a self-consistent manner. Simulation compares well with the experimental results and allows study of temperature rise – the root cause of thermal instability – for the emitter in a wide range of conditions. Our analysis suggests that higher thermal conductivity and/or electrical conductivity and their reduced temperature dependence are beneficial for the field emitters, as these improve the thermal stability of the emitter by reducing temperature rise.

Recent developments in monolayer graphene production allow its use as the active layer in field-effect transistor technology. Favorable electrical characteristics of monolayer graphene include high mobility, operating frequency, and good stability. These characteristics are governed by such key transport physical phenomena as electron-hole transport symmetry, Dirac point voltage, and charged impurity effects. Doping of graphene occurs during device fabrication, and is largely due to charged impurities located at or near the graphene/substrate interface. These impurities cause scattering of charge carriers, which lowers mobility. Such scattering is detrimental to graphene transistor performance, but our group has shown that coating with fluoropolymer thin films or exposure to polar organic vapors can restore favorable electrical characteristics to monolayer graphene. By partially neutralizing charged impurities and defects, we can improve the mobility by approximately a factor of 2, change the Dirac voltage by fairly large amounts, and reduce the residual carrier density significantly. We hypothesize that this phenomena results from screening of charged impurities by the polar molecules. To better understand such screening interactions, we performed computational chemistry experiments to observe interactions between polar organic molecules and monolayer graphene. The molecules interacted more strongly with defective graphene than with pristine graphene, and the electronic environment of graphene was altered. These computational observations correlate well with our experimental results to support our hypothesis that polar molecules can act to screen charged impurities on or near monolayer graphene. Such screening favorably mitigates charge scattering, improving graphene transistor performance.

We demonstrate the operation of a graphene-passivated on-chip porous silicon material as a high rate lithium ion battery anode with over 50x power density and 100x energy density improvement compared to identically prepared on-chip porous silicon supercapacitors. We demonstrate this Faradaic storage behavior to occur at fast charging rates (1-10 mA/cm2) where lithium locally intercalates into the nanoporous silicon, but not underlying bulk silicon material. This prevents the degradation and poor cycling performance that is commonly observed from deep storage in bulk silicon materials. As a result, this device exhibits cycling performance that exceeds 10,000 cycles with capacity above 0.1 mAh/cm2, without notable capacity fade. This work demonstrates a practical route toward high power, high energy, and long lifetime all-silicon on-chip storage systems relevant toward integration of energy storage into electronics, photovoltaics, and other silicon-based technology.

Two-dimensional (2D) materials has attracted intense interest in research in recent years. As compared to their bulk counterparts, these 2D materials have many unique properties due to their reduced dimensionality and symmetry. A key difference is the band structures, which lead to distinct electronic and photonic properties. The 2D nature of the materials also plays an important role in defining their exceptional properties of mechanical strength, surface sensitivity, thermal conductivity, tunable band-gap and interaction with light. These unique properties of 2D materials open up broad territories of applications in computing, communication, energy, and medicine. In this talk, I will present our work on understanding the electrical properties of graphene and MoS2, in particular current transport and band-gap engineering in graphene, interface between gate dielectrics and graphene, and gap states in MoS2. I will also present our work on the nano-scale electronic devices (RF and logic devices) and photonic devices (plasmonic devices and photo-detectors) based on graphene and transition metal dichalcogenides.

Layered transition metal dichalcogenide (TMDC) with hexagonal lattice structure has six valleys at corners of the Brillouin zone. The nontrivial Berry curvature distribution renders the adjacent valleys with distinguishable valley angular momentum, which enables itself as an ideal 2D valleytronic platform. Recent studies reported strong excitonic effect in monolayer WS2 and each excitonic state is identified with a well-defined orbital angular momentum, however the anticipated selection rules involve nonlinear optical processes are not clear. Here we show valley angular momentum (VAM) together with exciton angular momentum (EAM) impose different valley-exciton locked selection rules for second harmonic generation (SHG) and two photon luminescence (TPL) in monolayer WS2. Moreover, the two-photon induced valley populations yield net circular polarized photoluminescence after a sub-ps interexciton relaxation. The work demonstrates a new approach to control valley population at different excitonic states for next generation of optical circuits and quantum information computing.

The second harmonic generation (SHG) produced from two-dimensional atomic crystals have been utilized recently in studying the grain boundaries and electronic structure of such ultra-thin materials. However, the SHG in many of these crystals, such as transition metal dichalcogenides (TMDCs), only occur in odd numbered layers with limited intensity due to their noncentrosymmetric nature. Here, we probe the SHG from the bulk noncentrosymmetric molybdenum disulfide (MoS2). Whereas the commonly studied 2H crystal phase’s anti-parallel nonlinear dipoles in adjacent layers give an oscillatory SH response, the parallel nonlinear dipoles of each atomic layer in the 3R phase constructively interfere to amplify the nonlinear light. Due to this interference, we observed the atomically phase-matched condition yielding a quadratic dependence between the intensity and layer number. Additionally, we probed the layer evolution of the A and B excitonic transitions in 3R-MoS2 using SHG spectroscopy and found distinct electronic structure differences arising from the crystal geometry. These findings demonstrate the dramatic effect of the symmetry and layer stacking of these atomic crystals.

Laser enables the achievement of superb interfacial characteristics between electrode and semiconducting material contact surface and is also useful for a reduction in contact resistance. The irradiation of a pulsed laser with high energy density and short wavelength onto the electrodes leads to thermal annealing at the locally confined small area that needs high temperature without inflicting thermal damage. This contrasts conventional thermal annealing that affects the entire panel, including unwanted areas in which the annealing process should be excluded. We demonstrate that mechanically flexible and optically transparent (more than 81% transmittance in visible wavelength) multilayered molybdenum disulfide (MoS2) thin-film transistors (TFTs) in which the source/drain electrodes are selectively annealed using picosecond laser achieve the enhancement of device performance without plastic deformation, such as higher mobility, increased output resistance, and decreased subthreshold swing. Numerical thermal simulation for the temperature distribution, transmission electron microscopy (TEM) analysis, current-voltage measurements, and contact-free mobility extracted from the Y-function method (YFM) enable understanding of the compatibility and the effects of pulsed laser annealing process; the enhanced performance originated not only from a decrease in the Schottky barrier effect at the contact, but also an improvement of the channel interface. Furthermore, these results show that the laser annealing can be a promising technology to build up a high performance transparent and flexible electronics.

Tin disulfide displays a wide range of attractive physical and chemical properties and are potentially important for various device applications including nanoelectronics, optoelectronics, as well as energy conversion. Here, we report on the largescale synthesis of tin disulfide granular thin films on silicon dioxide substrates by soft chalcogenization method in which the pre-deposited tin thin films are transformed into tin disulfide thin films via exposure to sulfur vapor. The obtained tin disulfide films have been comprehensively characterized to study their fundamental properties in detail by using atomic force microscopy, scanning electron microcopy, Raman spectroscopy, photoluminescence spectroscopy and X-ray photoelectron spectroscopy.

We report on the development and characterization of a simple two-terminal non-volatile graphene switch. After an initial electroforming step during which Joule heating leads to the formation of a nano-gap impeding the current flow, the devices can be switched reversibly between two well-separated resistance states. To do so, either voltage sweeps or pulses can be used, with the condition that V_SET < V_RESET , where SET is the process decreasing the resistance and RESET the process increasing the resistance. We achieve reversible switching on more than 100 cycles with resistance ratio values of 10⁴. This approach of graphene memory is competitive as compared to other graphene approaches such as redox of graphene oxide, or electro-mechanical switches with suspended graphene. We suggest a switching model based on a planar electro-mechanical switch, whereby electrostatic, elastic and friction forces are competing to switch devices ON and OFF, and the stability in the ON state is achieved by the formation of covalent bonds between the two stretched sides of the graphene, hence bridging the nano-gap. Developing a planar electro-mechanical switch enables to obtain the advantages of electro-mechanical switches while avoiding most of their drawbacks.

Large attention has been directed toward carbon nanotubes as material for chemical sensors. However, little attention was paid toward the different behavior of the metallic and semiconductive carbon nanotubes as optical sensing materials. Semiconductive or metallic Single Wall Carbon Nanotubes (SWCNTs) have been deposited on gold nanoparticles (NPs) monolayer and used as plasmonic based gas sensor. The coupling between SWCNTs and Au NPs has the aim of combining the reactivity of the nanotubes towards hazardous gases, such as H2, CO, NO2, with the Localized Surface Plasmon Resonance (LSPR) of gold NPs. The LSPR is known to be extremely sensitive to the changes in the dielectric properties of the surrounding medium, a characteristic that has been widely exploited for the preparation of sensing devices. While the use of SWCNTs for gas sensing has been covered in multiple reports, to the best of our knowledge this is the first time that SWCNTs are used as sensing material in an optical sensor for the detection of reducing and oxidizing gases. Two different techniques, ink-jet printer and dropcasting, were used for depositing the transparent CNTs film on the plasmonic layer. Both the deposition techniques proved to be effective for the development of transparent optical sensing films. Metallic SWCNTs showed high sensitivity toward H2 at low temperature and an enhancement of performance at 300°C with the detection of low concentration of H2 and NO2. On the contrary, the semiconductive SWCNTs displayed very poor gas sensing properties, especially for the thinner film.

Phase change memory (PCM), with its long history, may now hold its brightest promise to date. This bright future is being fueled by the "push" from big data. PCM is a non-volatile memory technology used to create solid-state random access memory devices that operate based the resistance properties of materials. Employing the electrical resistance differences-as opposed to differences in charge stored-between the amorphous and crystalline phases of the material, PCM can store bits, namely one’s and zero’s. Indeed, owing to the method of storage, PCM can in fact be designed to hold multiple bits thus leading to a high-density technology twice the storage density and less than half the cost of DRAM, the main kind found in typical personal computers. It has been long known that PCM can fill a need gap that spans 3 decades in performance from DRAM to solid state drive (NAND Flash). Furthermore, PCM devices can lead to performance and reliability improvements essential to enabling significant steps forward to supporting big data centric computing. This talk will focus on the science and challenges of aggressive scaling to realize the density needed, how this scaling challenge is intertwined with materials needs for endurance into the giga-cycles, and the associated forefront research aiming to realizing multi-level functionality into these nanoscale programmable resistor devices.

Photodetector based on carbon nanotubes (CNT) was investigated. Sensors were done on quartz and silicon susbtrate. Samples of photodetectors sensors were produced by planar technology. This technology included deposition of first metal layer (Al), lithography for pads formation, etching, and formation of local catalyst area by inverse lithography. Vertically-aligned multi-wall carbon nanotubes were directly synthesized on substrate by PECVD method. I-V analysis and spectrum sensitivity of photodetector were investigated for 0.4 μm - 1.2 μm wavelength. Resistivity of CNT layers over temperature was detected in the range of -20°C to 100°C.

This paper describes a new technique, termed "metal-assisted exfoliation," for the scalable transfer of graphene from catalytic copper foils to flexible polymeric supports. The process is amenable to roll-to-roll manufacturing, and the copper substrate can be recycled. We then demonstrate the use of single-layer graphene as a template for the formation of sub-nanometer plasmonic gaps using a scalable fabrication process called “nanoskiving.” These gaps are formed between parallel gold nanowires in a process that first produces three-layer thin films with the architecture gold/single-layer graphene/gold, and then sections the composite films with an ultramicrotome. The structures produced can be treated as two gold nanowires separated along their entire lengths by an atomically thin graphene nanoribbon. Oxygen plasma etches the sandwiched graphene to a finite depth; this action produces a sub-nanometer gap near the top surface of the junction between the wires that is capable of supporting highly confined optical fields. The confinement of light is confirmed by surface-enhanced Raman spectroscopy measurements, which indicate that the enhancement of the electric field arises from the junction between the gold nanowires. These experiments demonstrate nanoskiving as a unique and easy-to-implement fabrication technique that is capable of forming sub-nanometer plasmonic gaps between parallel metallic nanostructures over long, macroscopic distances. These structures could be valuable for fundamental investigations as well as applications in plasmonics and molecular electronics.

Graphene growth of high crystal quality and single-layer thickness can be achieved by low pressure sublimation (LPS) on SiC(0001). On SiC(0001), which is the C-terminated polar surface, there has been much less success growing uniform, single-layer films. In this work, a systematic study of surface preparation by hydrogen etching followed by LPS in an argon ambient was performed. Hydrogen etching is an important first step in the graphene growth process because it removes damage caused by polishing the substrate surface. However, for SiC(0001), etching at too high of a temperature or for too long has been found to result in pit formation due to the preferential etching of screw dislocations that intersect the surface. It was found that temperatures above 1450°C in 200mbar of hydrogen result in pitting of the surface, whereas etch temperatures at and below 1450°C can result in atomically at terraces of ~ 1 µm width. Following the hydrogen etch optimization, argon-mediated graphene growth was carried out at several different temperatures. For the growth experiments, pressure and growth time were both fixed. Regardless of growth temperature, all of the films were found to have non-uniform thickness. Further, x-ray photoelectron spectroscopy and low energy electron diffraction measurements reveal that trace amounts of oxygen, which may be present during growth, significantly affects the graphene growth process on this polar surface.

This paper reviews some of the recent theoretical investigations on the Rashba Dresselhaus spin effects and dielectric properties of CH3NH3PbI3 hybrid perovskites and CsPbI3 all-inorganic perovskites using Density functional theory. The spin vectors rotate in the non-centrosymmetric P4mm tetragonal phase, respectively clockwise and counterclockwise, in a manner that is characteristic of a pure Rashba effect. The high frequency dielectric constants ε∞ of MAPbI3 and CsPbI3 are similar as anticipated, since large differences are only expected at very low frequency where additional contributions from molecular reorientations show off for the hybrid compounds. A first simulation of a perovskite on silicon tandem cell, including a tunnel junction, is also investigated. Effect of halogen substitution (I/Br) is inspected, revealing limitations for short-circuit current and open-circuit voltage electrical characteristics.

The requirement for long-range structure coherence and property uniformity for graphene-based electronics are crucial for their applications in electronics. Here, we briefly review our recent progress on synthesis of large-size graphene by seeded growth method. We demonstrate a seeded growth method which allows us to reduce the nucleation density in early stage of Chemical Vapor Deposition (CVD) leading to the production of low density of graphene grains and consequently achieve grain size of sub-centimeter. We further demonstrate that we can amplify the graphene grain size by limiting the second seeded growth only from the graphene seed edges. Moreover, we demonstrate that similar method can be used for the preparation of large-grain bilayer graphene flakes.

Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades, single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability. Nanoscale thermos-capillary flows in thin-film organic coatings followed by reactive ion etching serve as highly efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust, scalable operation, with clear potential for practical use. Especially for the purpose of selective joule heating over only metallic nanotubes, two representative platforms are proposed and confirmed. One is achieved by selective joule heating associated with thin film transistors with partial gate structure. The other is based on a simple, scalable, large-area scheme through microwave irradiation by using micro-strip dipole antennas of low work-function metals. In this study, based on purified semiconducting SWNTs, we demonstrated field effect transistors with mobility (> 1,000 cm²/Vsec) and on/off switching ratio (~10,000) with current outputs in the milliamp range. Furthermore, as one demonstration of the effectiveness over large area-scalability and simplicity, implementing the micro-wave based purification, on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.

Raman spectroscopy is known to provide information about the quality of the single walled carbon nanotubes (SWCNT). The information is based on the intensity ratio of D and G spectral modes and the frequency of RBM modes. However due to resonance nature of Raman spectrum of the nanotubes this method is not suitable to detect functionalization of the nanotubes. Surface enhanced Raman spectroscopy (SERS) is known to enhance the Raman bands up to fourteen orders of magnitude. Preferable adsorption sites for small silver nanoparticles are expected to be the functional groups of SWCNT; therefore SERS technique allows detecting small amounts of functional groups despite strong resonance Raman from backbone of SWCNT. In this study functionalized nanotubes were dispersed in silver colloid and dried on the standard silver plate for Raman measurements. Spectra of SWCNT without colloid in the spectral range between 50 and 1800 cm^-1 exhibit only four main spectral features: G, D, and RBM modes between 200 and 400 cm^-1. Spectra of SWCNT with the colloid exhibit several additional spectral bands which do not belong to the colloid. These bands attributed to vibrations of C-O, C-C and O-H from the functional groups and the carbon atom of the SWCNT attached to the corresponding group. The bands associated with the vibrations involving O atom is an indication that silver nanoparticles interact with the functional group attached to SWCNT.

Graphite oxide (GO) derived materials include chemically functionalize or reduced graphene oxide (exfoliated from GO) sheets, assembled paper-like forms , and graphene-based composites GO consists of intact graphitic regions interspersed with sp3-hybridized carbons containing hydroxyl and epoxide functional groups on the top and bottom surfaces of each sheet and sp2-hybridized carbons containing carboxyl and carbonyl groups mostly at the sheet edges. Hence, GO is hydrophilic and readily disperses in water to form stable colloidal suspensions Due to the attached oxygen functional groups, GO was used to prepare different derivatives which result in some physical and chemical properties that are dramatically different from their bulk counterparts .The present work discusses the covalent cross linking of graphite oxide to benzocaine or ethyl ester of para-aminobenzoic acid,structure I,used in many over-the-counter ointment drug.Synthesis is done via diazotization of the amino group.The product is characterized via IR,Raman, X-ray photoelectron spectroscopy as well as electron microscopy.