Scanning noise microscopy on graphene devices.

We developed a scanning noise microscopy (SNM) method and demonstrated the nanoscale noise analysis of a graphene strip-based device. Here, a Pt tip made a direct contact on the surface of a nanodevice to measure the current noise spectrum through it. Then, the measured noise spectrum was analyzed by an empirical model to extract the noise characteristics only from the device channel. As a proof of concept, we demonstrated the scaling behavior analysis of the noise in graphene strips. Furthermore, we performed the nanoscale noise mapping on a graphene channel, allowing us to study the effect of structural defects on the noise of the graphene channel. The SNM method is a powerful tool for nanoscale noise analysis and should play a significant role in basic research on nanoscale devices.

Universal parameters for carbon nanotube network-based sensors: can nanotube sensors be reproducible?

Carbon nanotube (CNT) network-based sensors have been often considered unsuitable for practical applications due to their unpredictable characteristics. Herein, we report the study of universal parameters which can be used to characterize CNT network-based sensors and make their response predictable. A theoretical model is proposed to explain these parameters, and sensing experiments for mercury (Hg(2+)) and ammonium (NH(4)(+)) ions using CNT network-based sensors were performed to confirm the validity of our model.

Uniform patterning of sub-50-nm-scale Au nanostructures on insulating solid substrate via dip-pen nanolithography.

We report a direct deposition strategy for sub-50-nm-scale uniform Au patterns on virtually any general insulating substrate via dip-pen nanolithography (DPN). In that process, HAuCl(4) molecules were deposited onto bare insulating substrates via a molecular diffusion process, in the absence of electrochemical reactions. Subsequently, the generated HAuCl(4) molecular patterns were decomposed to leave Au-only patterns using a thermal annealing process. Uniform Au patterns with a mean diameter of 47.9 +/- 3.1 nm were achieved after the annealing process. The strategy allowed us to generate Au patterns on virtually any general insulating substrate (e.g., SiO(2), Al(2)O(3), polyimide, etc) without the need for surface functionalization or additional electrode structures. This versatile and reliable patterning method is expected to be useful in the future development of various novel industrial applications (e.g., mask or nanocircuit repair, nanosensors, etc.).