DPN-Generated Nanostructures Made of Gold, Silver, and Palladium

Dip-pen nanolithography (DPN) has been used to generate resist layers on Au, Ag, and Pd that when combined with wet-chemical etching can lead to nanostructures with deliberately designed shapes and sizes. Monolayers of mercaptohexadecanoic acid (MHA) or octadecanethiol (ODT), patterned by DPN, were explored as etch resists. They work comparably well on Au and Ag, but ODT is the superior material for Pd. MHA seems to attract the FeCl₃ etchant and results in nonuniform etching of the underlying Pd substrate. Dots, lines, triangles, and circles, ranging in size from sub-100 to several hundred nanometers have been fabricated on Si/SiO_x substrates. These results show how one can use DPN as an alternative to more complex and costly procedures such as electron beam lithography to generate nanostructures from inorganic materials.