01 Nov 2007
US researchers have demonstrated self-assembled tungsten nanogratings with highly uniform grating periods and tooth lengths that can be easily tuned during the fabrication process.
The team, from the University of North Carolina at Charlotte, US, deposited tungsten nanogratings onto sapphire substrates using laser-induced chemical vapor deposition. (Nanotechnology 18 485304).
The laser pulse energy used in the deposition process was less than half a nanojoule, which is hundreds of times lower than the pulse energy necessary for other techniques used to fabricate sub-wavelength periodic nanostructures.
The team used scanning electron microscopy (SEM) to image the nanogratings, which showed very good uniformity in both the grating period and tooth length. By controlling the laser power and scanning speed, the grating period could be tuned from 153 to 185 nm and the grating tooth length from 480 to 890 nm.
The researchers show that nanogratings can be easily fabricated on non-planar substrates such as glass optical fibers, and large-area patterning is feasible by multiple scans with appropriate offsets between scans.
The team also suggests a model to qualitatively account for the anisotropic shape and the periodic appearance of the observed tungsten nanogratings.