Electrical Conductivity and Optical Properties of Nanoscale Titanium Films on Sapphire for Localized Plasmon Resonance-Based Sensors

The developing area of plasmonics has led to the possibility of creating a new type of high-speed, high-sensitivity optical sensor for biological environment analysis. The functional layer of such biosensors are nanoscale films of noble metals. In this work we suggest using a thin film of titanium as a functional layer. This paper presents the results of the research on electrical and optical characteristics of 5 to 80 nm thick titanium films deposited on sapphire substrates by magnetron sputtering. It is shown that surface plasmon resonance is consistently observed in the investigated titanium films and the theoretical grounds of surface plasmon resonance excitement is given. In structures with titanium films less than 15 nm thick, local plasmon resonance is observed along with surface plasmon resonance. Local plasmon resonance is more sensitive to the surface state of a thin film of titanium, which on the one hand increases the sensitivity of a biosensor, and on the other hand imposes restrictions on the parameters of nanoscale films.

Experimental Evidence of Two-fold Electromagnetic Enhancement Mechanism of Surface-Enhanced Raman Scattering

The surface-enhanced Raman scattering (SERS) electromagnetic (EM) enhancement mechanism is a two-fold enhancement process in which both the incident and scattered Raman fields are enhanced. In this letter, we present new direct evidence of the two-fold EM mechanism by using an Ag nanorod array/SiO₂ dielectric layer/Ag mirror multilayer thin film "local plasmon resonator". The two-fold EM enhancement mechanism of SERS was confirmed by analyzing the optical absorption and Raman scattering spectra of the local plasmon resonator for excitation and scattered light. The effect of light interference was altered by varying the film thickness of the SiO₂ phase control layer (PCL), and the absorbance in the Raman scattering wavelength range was reduced from 90% to 0%. We also demonstrated that the intensity of the background emission is closely related to the enhancement of the scattered field and provides substantial evidence for a two-fold SERS enhancement mechanism.

Experimental Evidence of Two-fold Electromagnetic Enhancement Mechanism of Surface-Enhanced Raman Scattering

The surface-enhanced Raman scattering (SERS) electromagnetic (EM) enhancement mechanism is a two-fold enhancement process in which both the incident and scattered Raman fields are enhanced. In this letter, we present new direct evidence of the two-fold EM mechanism by using an Ag nanorod array/SiO₂ dielectric layer/Ag mirror multilayer thin film "local plasmon resonator". The two-fold EM enhancement mechanism of SERS was confirmed by analyzing the optical absorption and Raman scattering spectra of the local plasmon resonator for excitation and scattered light. The effect of light interference was altered by varying the film thickness of the SiO₂ phase control layer (PCL), and the absorbance in the Raman scattering wavelength range was reduced from 90% to 0%. We also demonstrated that the intensity of the background emission is closely related to the enhancement of the scattered field and provides substantial evidence for a two-fold SERS enhancement mechanism.