Surface-enhanced Raman scattering substrates of flat and wrinkly titanium nitride thin films by sputter deposition

Titanium nitride (TiN) thin films were prepared by RF magnetron sputtering on a bare Si surface and a silicone-oil-covered Si surface as surface-enhanced Raman scattering (SERS) substrates. The TiN film deposited on the bare Si surface had a flat surface with densely packed grains measuring 18 nm in diameter, whereas the TiN film deposited on the oil surface had a wrinkly pattern made of grains measuring 19 nm in diameter. To analyze the SERS effect, Rhodamine 6G (R6G) was used as a Raman probe molecule at various concentrations ranging from 10−4 to 10−8 M. The analytical enhancement factor (AEF) values at 10−6 M R6G were respectively 6.2 × 103 and 1.3 × 104 for the flat TiN film and wrinkly TiN film. The SERS effect could be attributed to the enhancement of the local electromagnetic field at the top of the nano-sized grains. The wrinkly TiN film had a higher AEF than the flat TiN film, possibly due to the increased area of the Raman active spots. The wrinkly TiN film exhibited high level of SERS activity and achieved an R6G detection limit of 10−8 M.