Plasmonic enhanced photoconductivity of gold nano-island film in total internal reflection condition

The effect of total internal reflection (TIR) condition on the photoconductivity of gold nano-island film is investigated experimentally. The current-voltage measurements are carried out across the discontinuous film while it is excited under continuous wave (CW) low laser irradiance at wavelength of 532 nm, which appropriately matches the localized surface plasmon resonance (LSPR). The results show that the photoconductance of the gold nano-island film significantly increases when the incident angle of the laser irradiance is slightly greater than the critical angle. The enhanced photoconductivity of the gold nano-island film in TIR condition is attributed to the additional plasmonic-induced AC voltage. The experimental results are found to be in good agreement with the Simmons electron tunneling model, which can well describe the mechanism of the conductivity enhancement in nano-islands. To validate the experimental results, a theoretical calculation for the critical angle is performed. The percentage difference between the experimental and theoretical values is found to be 22%, indicating that the experimental results are consistent with the established theoretical calculation. The enhanced photoconductivity of gold nanostructures in TIR condition holds significant potential for various applications, particularly in total internal reflection optical imaging instruments.