Preparation of self-assembled mercaptoalkanoic acid multilayers on GaAs (110) surfaces

Mono- and double layer films have been formed by the self-assembly of 16-mercapto-hexadecanoic acid, (MHDA), HS(CH2)(15)COOH, via selective ionic interaction. To understand the formation process in the nanometer length scale, atomic force microscopy (AFM) studies have been conducted in combination with micro X-ray photoelectron spectroscopy (mu-XPS), Auger electron spectroscopy (AES) and-micro-fourier transform infrared spectroscopy with the attenuated total reflection method (mu-FTIR ATR). After the formation of a self-assembled monolayer (SAM) was completed,. the surface treated with copper ions was immersed in a solution of MHDA. By this method, an atomically smooth double layer was successfully formed on cleaved GaAs (110)surfaces. The formation speed of the second layer was faster Wan that of the SAM, indicating stronger interaction of thiol functional groups with Cu2+ ions than with GaAs surfaces.