Berkeley Lab Researchers Ink Nanostructures with Tiny ‘Soldering Iron’
Thermal dip-pen nanolithography
turns the tip of a scanning probe
microscope into a tiny soldering iron
that can be used to draw chemical
patterns as small as 20 nanometers
(Image courtesy of DeYoreo, et. al)
One way of directly writing nanoscale structures onto a substrate is to use an atomic force microscope (AFM) tip as a pen to deposit ink molecules through molecular diffusion onto the surface. Unlike conventional nanofabrication techniques that are expensive, require specialized environments and usually work with only a few materials, this technique, called dip-pen nanolithography, can be used in almost any environment to write many different chemical compounds. A cousin of this technique — called thermal dip-pen nanolithography — extends this technique to solid materials by turning an AFM tip into a tiny soldering iron.
Dip-pen nanolithography can be used to pattern features as small as 20 nanometers, more than forty thousand times smaller than the width of a human hair. What’s more, the writing tip also performs as a surface profiler, allowing a freshly-writ surface to be imaged with nanoscale precision immediately after patterning.
“Tip-based manufacturing holds real promise for precise fabrication of nanoscale devices,” says Jim DeYoreo, interim director of Berkeley Lab’s Molecular Foundry, a DOE nanoscience research center. “However, a robust technology requires a scientific foundation built on an understanding of material transfer during this process. Our study is the first to provide this fundamental understanding of thermal dip-pen nanolithography.”
In this study, DeYoreo and coworkers systematically investigated the effect of temperature on feature size. Using their results, the team developed a new model to deconstruct how ink molecules travel from the writing tip to the substrate, assemble into an ordered layer and grow into a nanoscale feature.
“By carefully considering the role of temperature in thermal dip-pen nanolithography, we may be able to design and fabricate nanoscale patterns of materials ranging from small molecules to polymers with better control over feature sizes and shapes on a variety of substrates,” says Sungwook Chung, a staff scientist in Berkeley Lab’s Physical Biosciences Division, and Foundry user working with DeYoreo. “This technique helps overcome fundamental length scale limitations without the need for complex growth methods.”
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For more information about the Molecular Foundry visit the Website athttp://foundry.lbl.gov/