Influence of temperature dependent morphology on localized surface plasmon resonance in ultra-thin silver island films

摘要

Dependence of morphological evolution and variation of corresponding localized surface plasmonic properties of the ultra-thin Ag island films deposited by thermal evaporation at different substrate temperatures have been investigated. It has been observed that the particle diameter, height, aspect ratio, surface coverage, roughness and particle density of the films are strongly dependent on the substrate temperature and film thickness. Depending on the trend of the shift of localized surface plasmon dip overall thermal process is divided into two stages: in first stage apparent change in localized surface plasmon dip takes place with the shift towards the shorter wavelengths. In the second stage, it is red shifted. Both these changes can be attributed to the change of morphology of the Ag island films. Strong temperature dependence between the morphological evolution and optical properties variation has been observed. Bandwidth, position and relative intensity of localized surface plasmon resonance induced absorption dip have been correlated with various morphological characteristics. Effective medium extended Maxwell-Garnett theory is used to simulate the optical transparency of these Ag metal island thin films. With the increment of substrate temperature up to 250℃ these silver metal island thin films exhibit high optical transparency in the range 600-1100 nm.