Highly Sensitive and Transparent Surface Enhanced Raman Scattering Substrates Made by Active Coldly Condensed Ag Nanorod Arrays

We report a simple and robust method to fabricate highly sensitive and transparent silver nanorod (AgNR) array substrates for surface enhanced Raman scattering (SEAS) using low temperature oblique angle deposition technique. These highly sensitive AgNR SERS substrates consist of tilted AgNRs deposited on glass slides at a substrate temperature T = 140 K. The results show that the substrate temperature plays a crucial role in determining both the morphology and the length of AgNRs. The SERS enhancement activity of these substrates was determined using trans-1,2-bis(4-pyridyl) ethylene as a Raman probe molecule. The highest SERS response was obtained from 1 mu m long AgNRs fabricated at T = 140 K. Such a deposition reduces the deposition time to 1/4 when compared to similar length AgNRs deposited at room temperature. The effect of the manifestly different surface morphology of low temperature deposited AgNRs on the SERS enhancement is demonstrated by finite-difference time-domain calculations of local field enhancements. The AgNRs arrays grown at 140 K exhibit uniform SERS response and good optical transmission and are cost-effective, which makes this fabrication method a practical choice as a next generation alternative for SERS substrate fabrication.