Optical property of gold nanoparticles modified by plasma exposure and sputtering

Kawaguchi, Kazuhiro; Takahiro, Katsumi*; Yamamoto, Shunya; Yoshikawa, Masahito; Nagata, Shinji*

Optical absorption due to localized surface plasmon resonance (LSPR) of Au nanoparticles (Au NPs) is being applied to optical chemical sensors. In this work, ion sputtering and plasma cleaning have been employed to control the LSPR absorption. Au NPs on quartz and Si substrates were fabricated by RF magnetron sputtering method. The samples were characterized by UV-Vis extinction spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS). The peak position of LSPR absorption was shifted toward shorter wavelength after ion irradiation and plasma treatment. The SEM observation revealed that the average size of Au NPs did not change before and after ion irradiation and plasma treatment. The XPS analysis showed that the blue-shift of LSPR absorption was resulted from the elimination of hydrocarbons adhered on particle surfaces. We concluded that plasma and ion sputtering treatments are effective method to obtain Au NPs with clean surfaces.