Synthesis and SERS properties of tantalum nitride thin film via sol-gel method combined with ammonia reduction nitridation

Tantalum nitride thin films with excellent surface-enhanced Raman spectroscopy (SERS) properties were prepared using a sol-gel method combined with ammonia reduction and nitridation process. The phase composition, surface morphology, optical properties, and SERS properties of the thin films were characterized using various techniques. X-ray diffraction and X-ray photoelectron spectroscopy analyses showed that a solid solution of tantalum oxynitride (TaOxNy) was formed in the film, rather than the standard Ta3N5 crystal. As the reduction nitridation temperature increased, the surface roughness of the tantalum nitride thin film initially decreased and then increased. The tantalum nitride grains on the surface of the thin film provided more SERS ‘hot spots’. Ultraviolet–visible absorption spectra revealed that the characteristic surface plasmon resonance absorption peak of the tantalum nitride thin film was around 550 nm. Tantalum nitride thin film obtained at 1000 °C exhibited the best surface Raman enhancement performance. Using Rhodamine 6G as the Raman probe molecule, the detection limit for tantalum nitride film SERS substrate reached 10−7 M, with an enhancement factor of 7.23 × 103. Additionally, the tantalum nitride thin film exhibited good uniformity and long-term stability. The results demonstrated that tantalum nitride thin films could exhibit SERS activity through electromagnetic enhancement and charge transfer mechanisms. •The thin films were synthesized using sol-gel method combined with ammonia reduction nitridation.•Increasing the nitridation temperature enhances SPR peaks and amplifies the local electromagnetic field effect.•Raising the nitridation temperature narrows the forbidden bandwidth of tantalum nitride film, facilitating charge transfer with probe molecules.