Nanosphere Liftoff Lithography

If marbles are placed together on a board as tightly as possible, they will form a tight group, with each marble surrounded by six others. If this array were spray painted from the top, and then the marbles were tipped off the board, the paint would appear as a set of painted dots, each shaped like a triangle but with concave sides (see Figure 4.5). Now if the marbles are nanoscale, so are the paint dots. In fact, Figure 4.5 shows dots of silver metal prepared by Rick Van Duyne's group at Northwestern. The technique is called nanosphere liftoff lithography, even though no rockets are involved. It has several nice features: many sorts of boards (surfaces) and paints (metals, molecules) can be used, and several layers of paint (molecules) can be put down sequentially on the triangles. Importantly, this liftoff nanolithography, unlike DPN or scanning probe but like nanostamp, is parallel. Many nanospheres can be placed on the surface, so that regular arrays of many (thousands or more) dots can be prepared.

Figure 4.5. Schematic of the nanosphere liftoff lithography process.

Courtesy of the Van Duyne Group, Northwestern University.

Courtesy of the Van Duyne Group, Northwestern University.

Nanosphere Lithography

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