Aligned carbon nanotubes (CNT’s) have been found to form on both the Si and C faces of silicon carbide (SiC) wafers at high temperature. The CNT’s form when the SiC wafer is exposed to temperatures in the range 1400-1700°C under moderate vacuum. The CNT’s are aligned roughly parallel to the surface. After a half hour at 1700°C under vacuum of 10-4torr, a near continuous CNT layer about 250nm thick is formed. The entire surface of the SiC is covered with CNT’s including both single and multiwalled tubes, and some graphitic carbon. SEM, TEM, AFM, XPS and Raman scattering measurements have been used to analyse the CNT/SiC structures. The metal catalyst free CNT’s on SiC exhibit low density of structural defects and are very straight. The carbon source is believed to be residual carbon from the SiC left on the surface after preferential evaporation of Si. It is speculated that CNT's growth is catalysed by low concentrations of residual oxygen in the chamber during growth. The vacuum conditions can significantly affect CNT's growth. Single wall carbon nanotubes are evident in Raman spectra on the samples grown at 10-3 Torr, not on these grown at 10-5Torr.
Holography offers a versatile, rapid and volume scalable approach for making large area, multi-dimensional, organic PBGs; however, the small refractive index contrast of organics prevents formation of a complete band-gap. The introduction of inorganic nanoparticles to the structure provides a possible solution. In contrast to the multiple steps (exposure, development and infiltration) necessitated by lithographic-based holography (e.g. photoresists), holographic photopolymerization of monomer-nanoparticle suspensions enables one-step fabrication of multidimensional organic-inorganic photonic band gap (PBG) structures with high refractive index contrast. The PBGs are formed by segregation of semiconductor nanocrystals during polymerization of the polymer network. Addition of CdSe/ZnS polymerization of the highly cross-linked polymer network. Addition of CdSe/ZnS quantum dots or ZnO nanocrystals to the H-PDLCs formulation results in phase segregation of the nanoparticles into the liquid crystal rich lamellae, producing photonic structures with high diffraction efficiencies that may be modulated by application of an external electric field.
Recently, there has been increased interest in polymer-based photovoltaic devices due to their promise for the creation of lightweight, flexible, and inexpensive electrical power. WE examined the possibility of using nanoparticles and nanoparticles with tailored interfaces for the creation of hybrid polymer-based devices with enhanced photovoltaic response. Initially, we investigated the incorporation of multi-walled carbon nanotubes (MWNT) in the poly(benzimidazo-benzophenanthroline) ladder (BBL) layer of two-layer poly(p-phenylene vinylene)(PPV)-BBL photovoltaic devices. Subsequently, we explored the possibility of tuning polymer-particle interfaces through the creation of core-shell particles fabricated using electrostatic self- assembly. For the PPV/BBL(MWNT) devices, a doubling of the photocurrent and a drastic reduction in photovoltage with MWNT incorporation is observed for a range of BBL layer thickness values. This behavior is consistent with the MWNTs functioning as a three dimensional extension of the top aluminum electrode. Fabrication studies on core-shell particles demonstrate that the interfacial properties of a variety of particles can be manipulated, shells of up to 10 bilayers can be achieved, and TiO2 nanoparticles with PPV polymer shells are possible.