Electrical Characteristics of Horizontally and Vertically Oriented Few-Layer Graphene on Si-Based Dielectrics.

Horizontally and vertically oriented few-layer graphenes have been synthesized directly on SiO2 coated Si substrates via thermal and hot-filament chemical vapor deposition, respectively. The effect of the direction of mass flow on the fabrication of graphene film is analysed and a plausible mechanism is proposed. The graphene/p-Si heterojunction is fabricated and tested for its potential in optoelectronic devices. Rectification behaviour is observed at the interface of graphene/p-Si under dark conditions. A dark current of 1.1 mA with an ideality factor of 1.5, in addition of a high rectification ratio of 15.99 at ± 0.5 V is found for the vertically oriented graphene/p-Si heterojunction.

Optimizing Performance Parameters of Chemically-Derived Graphene/p-Si Heterojunction Solar Cell.

Chemically-derived graphene have been synthesized by modified Hummers method and reduced using sodium borohydride. To explore the potential for photovoltaic applications, graphene/p-silicon (Si) heterojunction devices were fabricated using a simple and cost effective technique called spin coating. The SEM analysis shows the formation of graphene oxide (GO) flakes which become smooth after reduction. The absence of oxygen containing functional groups, as observed in FT-IR spectra, reveals the reduction of GO, i.e., reduced graphene oxide (rGO). It was further confirmed by Raman analysis, which shows slight reduction in G-band intensity with respect to D-band. Hall effect measurement confirmed n-type nature of rGO. Therefore, an effort has been made to simu- late rGO/p-Si heterojunction device by using the one-dimensional solar cell capacitance software, considering the experimentally derived parameters. The detail analysis of the effects of Si thickness, graphene thickness and temperature on the performance of the device has been presented.

Transparent conductive multiwall carbon nanotubes-polymer composite for electrode applications.

Disperse Multiwall carbon nanotubes (MWCNTs) are incorporated aqueous N-hydroxy methyl acrylamide, which is subjected to crosslinking to develop a transparent conductive composite free standing film. The effects of the concentration of MWCNTs and temperature on optical and electrical properties of nano-composites are investigated. Interestingly, only 0.06 mg/ml of MWCNTs is sufficient to reach the percolation threshold (Phi) for transition in electrical conductivity up to 10(-4) S/cm, with a visible transmittance over 85%, which is well above the reported for such a low level of MWCNTs loading. The electrical conductivity of the composite was measured at 120 degrees C. It has been observed that electrical conductivity increases significantly with the increase in temperature, signifying the semiconducting nature of nano-composites. Finally, current-voltage (I-V) characteristics show liner behaviour, confirms Ohmic nature of nano-composites and metal contact.