Fabrication of nanowires follows two schemes: the bottom-up and the top-down approach. The initial studies on biomolecule detection used the first approach. Nanowires are grown using various techniques, which involve complex integration, poor reproducibility and lack the benefit of very large scale integration. Nanowires produced with the latter approach using electron-beam (e-beam) lithography are showing promising features but are not scalable for mass production today.
In a recent paper from our group (Nanotechnology 19 235201) we showed that so called nanoribbons, ~45 nm thick, ~1 µm wide, can work in a similar way as nanowires produced using growth techniques or e-beam lithography. The nanoribbons are fabricated in a two-step optical lithography process from ultra-thin silicon-on-insulator wafers with a technique from the 1980s. This relaxes complications in both fabrication approaches and is scalable for mass production today.
The sensitivity has been shown to a few protein molecules on the nanoribbon surface. The reason for the high sensitivity is shown in our paper, where the current is studied as charged molecules attach to the nanoribbon surface. The current path was altered from the “bottom“ of the silicon layer to the “top“, i.e. by a distance of <45 nm and the response was shown to increase by a factor of ~3. This shows the dependence on the local environment with respect to charges.
The nanoribbon approach shows that the great promise of nanotechnology providing highly sensitive, small, hand-held devices at a low cost can be realized using techniques from a time where nano was just a dream.