Nanoscale junctions for single molecule electronics fabricated using bilayer nanoimprint lithography combined with...

Area of Science:

• Nanotechnology
• Molecular Electronics
• Materials Science

Background:

• Nanoimprint lithography (NIL) offers cost-effective, high-throughput fabrication of nanoscale structures.
• Single-molecule electronic devices require precise fabrication of nanojunctions for reliable measurements.
• Existing NIL methods face challenges like metal side-wall tearing during lift-off.

Purpose of the Study:

• To develop an advanced bilayer NIL process for fabricating four-terminal nanojunction devices.
• To create stable, sub-2 nm nanogap electrodes using electromigration.
• To integrate and characterize molecular electronic properties using benzenethiol.

Main Methods:

• Utilized a bilayer resist technique for NIL lift-off, preventing metal tearing.
• Optimized imprint parameters and etching processes to create undercut resist structures.
• Employed feedback-controlled electromigration to form stable nanogap electrodes below 2 nm.
• Integrated benzenethiol molecules and performed current-voltage (I-V) measurements.

Main Results:

• Successfully demonstrated a NIL lift-off process negating side-wall tearing issues.
• Fabricated micron-sized features while maintaining bilayer structure for undercut formation.
• Achieved room-temperature stable nanogap electrodes with sizes less than 2 nm.
• Observed molecular transport signatures, including voltage-dependent current suppression and resonant transport through benzenethiol.

Conclusions:

• The advanced bilayer NIL approach is effective for fabricating nanojunction devices for molecular electronics.
• Electromigration enables the creation of stable, ultrasmall nanogaps suitable for single-molecule studies.
• Benzenethiol molecules bridge nanogaps via π-stacking, exhibiting characteristic electronic transport properties.