Self-assembled Au nanoparticles on GaAs and its surface enhanced Raman scattering(SERS)-activity

By using p-aminothiophenol(PATP) as the coupling molecular, the Au nanoparticles were successfully self-assembled onto the GaAs(100) surface. Firstly, the mechanically polished semi-insulating GaAs(100) wafers were degreased in trichloroethylene, acetone, methanol, and the surface oxides were chemically polished and removed by rinsing them in V(H2SO4) : V (H2O2) : V(H2O) = 3 : 1 : 1, V(NH4OH) : V(H2O2) : V(H2O) = 1 : 1 : 7, HCl and de-ionized water. Then the wafers were dried with argon and immediately immersed in 1 mmol/L ethanol solution of PATP. After assembling in the solution for 24 h with argon protection, the GaAs(100) wafers with PATP SAMs were ultrasonicated in pure ethanol to remove those physical adsorbed PATP molecules. Assembling of gold nanoparticles (70 nm) were handled by immersing thus prepared GaAs(100) wafers with PATP SAMs in a colloidal gold suspension for 6 h. The gold nanoparticles were scattered over such a surface. Thus the prepared samples showed a surface enhanced Raman scattering(SERS)-activity.