Large-area fabrication of Au nanoantennas for surface enhanced infrared spectroscopy without an adhesion layer

This work reports the fabrication of large-area Au nanoantennas, tuned to 1400cm^-1 on a Si substrate for surface-enhanced-infrared-absorption-spectroscopy. Two different kinds of nanoantennas are fabricated, namely nano-rods and nano-slits. Fabrication is achieved by E-beam lithography (EBL). The need for an adhesion layer is eliminated using our previously reported UV-ozone pre-treatment¹. To our knowledge, this is the first time this technique is used to fabricate Au nanoantennas on Si without the need adhesion layer, while at the same time obtaining a strong adhesion. This UV-ozone treatment does not only speed up the fabrication process, it can potentially increase the enhancement quality due to the negative influence metallic adhesion layers can have on the plasmon resonance of Au nanoantennas^2-4. Next to using the standard positive resist for EBL lithography, we also propose a workflow using a negative photoresist to make the nano-rod antennas, potentially speeding up the process by skipping the lift off procedure. Although the negative photoresist fabrication process still requires optimization, our first fabrication attempt show promising results. In order to get the optimal enhancement for a given wavelength, we used FTDT simulations to simulate the structure length, height, width and pitch. After successful simulations, the structures were fabricated and a comparison between the simulated results and fabricated structures was made, confirming the simulation results.