Transparent conductive electrodes (TCE) made of carbon nanotube (CNT) and graphene composite for GaN-based light emitting diodes (LED) are presented. The TCE with 533-/sheet resistance and 88% transmittance were obtained when chemical-vapor-deposition (CVD) grown graphene was fused across CNT networks. With an additional 2-nm thin NiOx interlayer between the TCE and top p-GaN layer of the LED, the forward voltage was reduced to 5.12 V at 20-mA injection current. Moreover, four-fold improvement in terms of light output power was also observed. The improvement can be ascribed to the enhanced lateral current spreading across the hybrid CNTgraphene TCE before injection into the p-GaN layer THE MANUSCRIPT Carbon-based materials, for example one-dimensional carbon nanotube (CNT) and two-dimensional graphene, have been of great interest in broad range of applications, such as field-emission devices 1,2 , sensors 3,4 , lithium-sulfur batteries 5,6 , supercapacitors 7 and field-effect transistors 8. Both of the sp 2-hybridized carbon materials possess superior thermal conductivity, mechanical robustness and high electrical conductivities. The fact that they are only several atomic layer thin make them highly transparent. They are viable alternatives for transparent conductive electrode (TCE) in place of indium tin oxide (ITO) that is known to have chemical instability, scarcity in supply and brittleness _____________________________
Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.
We have found that a Si wire array is formed by thermal agglomeration of an ultrathin (111) Si layer in a bonded silicon-on-insulator (SOI) structure, although previous studies for crystalline and amorphous Si layers on SiO2 only showed island formation. As starting material, (111) bonded SOI wafers with the top Si layers thinned to 5–9 nm were used. The samples were then subjected to a thermal treatment at 950 °C in an ultrahigh vacuum. Atomic force microscopy revealed that the (111) top Si layer is deformed into three sets of wire arrays in the three equivalent ⟨112¯⟩ directions. It is also shown that the patterning of a Si layer leads to the wire array selectively formed in one of these three directions.
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