August 30, 2004 - Researchers from the Georgia Institute of Technology and Naval Research Laboratory have improved upon a method to directly write nanometer-scale patterns onto various surfaces.

The "thermal dip pen nanolithography" technique is an extension of dip pen nanolithography used with atomic force microscopy (AFM), in which probe tips are coated with liquid ink that flows onto a surface to make patterns where the tip makes contact. The new technique uses easily melted solid inks and AFP probes with built-in heaters that essentially switch the writing on and off, so that the AFM tips can both sense surface patterns and write new ones. For solid inks, the researchers started by using octadecylphosphonic acid, which melts at 100 degrees C, and have moved on to other solders and polymers; using organic materials, they hope to produce a working semiconductor device by the end of this year.

So far the scientists have produced 90nm-wide lines, and claim the thermal dip pen could produce features as small as 10nm. Applications include semiconductor patterning with features smaller than available with light-based lithography; nanoscale soldering iron for repairing circuitry; and further research into nanotechnology phenomena.

The research also could extend into vacuum environments -- typical liquid-based inks would evaporate, but solid inks would bond to features, allowing them to be more compatible with conventional chip manufacturing processes, according to Lloyd Whitman, head of the Surface Nanoscience and Sensor Technology Section at the Naval Research Labs in Washington, DC.

"There are significant questions about how you define temperature at this size scale," said William King, assistant prof. in Georgia Tech's School of Mechanical Engineering. "This technology is helping us understand the science of nanoscale heat flow."