High Aspect Plasmonic Nanotrench Structures As Sensors In The Near- And Mid-Ir Frequency Range

Titanium nitride (TiN) and aluminum-doped zinc oxide (AZO) high-aspect trench structures are fabricated using a combination of deep reactive ion etching and atomic layer deposition. These structures may be used as sensors in the near-infrared (IR, 820 -900 nm wavelength range) and mid-IR (8 mu m wavelength), respectively. We show that the refractive index sensitivity reached values up to 430 nm/RIU for TiN trenches in the near-IR region and enhanced sensitivity of molecules in AZO trenches for mid-IR wavelengths.Due to the high achievable confinement of the electric field at a metal-dielectric interface, plasmons are one of the avenues exploited for high-sensitivity sensing [1]. This confinement at the surface allows tracking of very small amounts of analytes, for example in label-free biosensing. One of the possible designs of the sensors involves grating structures [2,3]. Depending on the analyte to be measured, either near-or mid-IR ranges can be used. In particular, the mid-IR absorption spectroscopy operating in the wavelength range of 2 -20 mu m (5000 500 cm(-1)) can be used to detect molecules by measuring the vibrational modes in their chemical bonds. They generally have specific absorption bands in this wavelength range [4-6], enabling label-free detection of specific molecules in solid, liquid, and gas phases. The research into these fields may enable various applications from medical diagnosis to gas sensing for environmental monitoring.