Annealing treatment of focused gallium ion beam processing of SERS gold substrate

Raman spectroscopy is a type of inelastic scattering spectroscopy that is widely used in determining and analyzing molecular structure. It also has a number of practical applications in evaluating food safety, medicine, and forensics. The Raman spectral signal is weak, but the development of the surface-enhanced Raman scattering (SERS) technique has overcome this problem and led to further developments in Raman spectroscopy. This paper describes a fundamental study of the use of focused ion beam (FIB) direct writing for preparing gold substrates for SERS. Molecular dynamics and Monte Carlo simulation methods are used to investigate the damage induced by gallium ion implantation of a gold substrate. Based on characterization by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy, the mechanism by which ion implantation and annealing influence the damage induced by a gallium FIB is analyzed. After annealing at 350 °C, a mixture of metallic gallium, its oxide Ga2O3 conforming to the stoichiometric ratio, and its sub-stable oxide (Ga2Ox) in sub-stoichiometric ratio precipitated on the surface are detected by XPS. Annealing treatment can effectively reduce the effect of gallium ion implantation on a SERS substrate fabricated by FIB direct writing.