Double layer lift-off nanofabrication controlled gaps of nanoelectrodes with sub-100 nm by nanoimprint lithography.

Basic research on nanoelectronics is often limited by the high cost and large-scale methods to fabricate electrodes with controlled gap size in nanometer scales. Here nanoelectrodes with a controlled gap size of sub-100 nm were fabricated by modified nanoimprint lithography (NIL) via a double-layer lift-off process utilizing polymethylmethacrylate (PMMA) and polydimethylglutarimide (PMGI) as the lift-off resist. Firstly the patterns of the electrode mold were transferred onto the upper PMMA layer by NIL techniques and then through controlling the developing time and concentration of developer of the PMGI under layer, regulating the exact gap size of the transferred metal nanoelectrode. The result indicated that the 'undercut' phenomenon was observed of the PMGI transfer layer during the developing process; through controlling the feature size of the undercut length, the gap size of the transferred metal nanoelectrode was precisely controlled, which showed shrinkage behavior. The nanoelectrodes with gap sizes of 800, 400, 200, and 100 nm can be reduced to about 440, 120, 80, and 70 nm. Our result provides a low-cost and large-scale route to prepare nanoelectrodes with controlled gap size, which can be valuable for current efforts in nanoelectronics.