The team synthesized a number of opal films with silica-sphere diameters from 200 to 650 nm. They used the ordered arrays of silica spheres as a support for Mo/Co catalyst particles. Then, by applying chemical-vapour deposition, they grew semiconductor-type single-walled carbon nanotubes with an average diameter of 0.9 nm on the opal surface.
"Single-walled carbon nanotubes are highly nonlinear and fast-switching materials," Haim Grebel told nanotechweb.org. "One can incorporate them into an optically confining environment to achieve these characteristics at relatively low levels of laser intensities."
The researchers tested the optical properties of the samples; transmission of light through the tubes increased with the incident laser intensity, while their current-voltage characteristics changed upon illumination with a laser beam. Raman scattering decreased as electrical biasing increased, and the structures also exhibited enhanced transmission for particular angles of light.
"These structures may be incorporated in fast, efficient, all-optical or electro-optical organic-based switches for communication and sensor systems," added Grebel. "In the future, one may use such structures to optoelectronically switch biological species."
Now, the scientists are aiming to determine the thermal, mechanical and environmental limitations of the structures. "In addition, one of the pressing problems in nanotechnology right now is the growth of individual single-walled carbon nanotubes at a precise location," added Grebel. "And our next challenge is to design and fabricate electro-optic interconnects."
The scientists reported their work in Applied Physics Letters.