Writing Conductive Lines with Hot Tips The interface within devices between conductors, semiconductors, and insulators is usually created by stacking patterned layers of different materials. For flexible electronics, it can be advantageous to avoid this architectural constraint. Graphene oxide, formed by chemical exfoliation of graphite, can be reduced to a more conductive form using chemical reductants. Wei et al. (p. 1373 ) now show that layers of graphene oxide can also be reduced using a hot atomic force microscope tip to create materials comparable to those of organic conductors. This process can create patterned regions (down to 12 nanometers in width) that differ in conductivity by up to four orders of magnitude.

We present the first microscopic transport study of epitaxial graphene on SiC using an ultrahigh vacuum four-probe scanning tunneling microscope. Anisotropic conductivity is observed that is caused by the interaction between the graphene and the underlying substrate. These results can be explained by a model where charge buildup at the step edges leads to local scattering of charge carriers. This highlights the importance of considering substrate effects in proposed devices that utilize nanoscale patterning of graphene on electrically isolated substrates.

We describe the deposition of continuous metal nanostructures onto glass and silicon using a heated atomic force microscope cantilever. Like a miniature soldering iron, the cantilever tip is coated with indium metal, which can be deposited onto a surface forming lines of a width less than 80 nm. Deposition is controlled using a heater integrated into the cantilever. When the cantilever is unheated, no metal is deposited from the tip, allowing the writing to be registered to existing features on the surface. We demonstrate direct-write circuit repair by writing an electrical connection between two metal electrodes separated by a submicron gap.

Graphene nanoribbons (GNRs) would be the ideal building blocks for all carbon electronics; however, many challenges remain in developing an appropriate nanolithography that generates high-quality ribbons in registry with other devices. Here we report direct and local fabrication of GNRs by thermochemical nanolithography, which uses a heated AFM probe to locally convert highly insulating graphene fluoride to conductive graphene. Chemically isolated GNRs as narrow as 40 nm show p-doping behavior and sheet resistances as low as 22.9 KΩ/□ in air, only approximately 10× higher than that of pristine graphene. The impact of probe temperature and speed are examined as well as the variable-temperature transport properties of the GNR.

No abstract