ELECTROCHEMICAL FORMATION OF CLOSE-PACKED PHENYL LAYERS ON SI(111)

4-NO2 and 4-Br benzenediazonium salts have been electrochemically redu ced on H-terminated Si(111) electrodes. Electrochemical measurements e vidence that the reaction results in a robust modification of Si(111) surfaces. XPS shows that organic films are monolayer thick and that co valent =Si-Ar bonding occurs, with no oxide at the interface. In the c ase of the Br salt, quantitative RES measurements suggest that layers are (2x1) close-packed and assess their stability against several rins ing procedures including exposure to 40% HF. A mechanism of grafting i s discussed.