Preparation and characterization of ultraclean H:Si(111)-(1×1) Surfaces Studied by HREELS, AFM and STM-STS

We review a wet chemical process to prepare the high quality hydrogen-terminated Si(111)-(1×1) surface and show that the two key issues for the high reproducibility are the etching time and the oxygen in the etching solution. We add ammonium sulfite to remove the oxygen according to the previous report [Appl. Surf. Sci. 130, 146 (1998)]. To elucidate the optimal etching time, the vibrational properties and the surface morphology are investigated by high-resolution electron-energy-loss spectroscopy (HREELS), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The HREELS spectra, and images of AFM and STM reveal the precise aqueous NH4F etching process of Si(111) and indicate the high controllability of steps and terraces with atomic scale. The surface cleanliness and morphology strongly depend on the etching time. At the etching time of 10 min, we obtain an ultra-clean and atomically ordered surface with wide terraces of 36 ± 7 nm step distance. It is confirmed by AFM and STM that the 1.0% ammonium sulfite is useful to remove dissolved oxygen in the 40% NH4F etching solution and to prepare a high quality H:Si(111)-(1×1) surface with low density of etch pits. The measurement of scanning tunneling spectroscopy(STS) shows the Schottky diode character of the surface. This surface is well applied to the initial stages of the nano-particle and film growth of Ag atoms and Pentacene molecules.