Invited Paper SS1-ThM5
Producing Ultraflat Si(100) Surfaces with Aqueous Etching: STM and FTIR Yield Mechanistic Insights

Thursday, October 23, 2008, 9:20 am, Room 207

The production of atomically flat Si(100) surfaces is a long-standing technological challenge, as Si(100) is the basis for today’s microelectronic devices. From a chemist’s standpoint, the study of etch morphologies yields fascinating insights into surface chemistry, as etching reactions literally write a record of their reactivity on the etched surface. We use a combination of STM and vibrational spectroscopy to show that a simple aqueous etchant can produce Si(100) surfaces of surprising and unprecedented smoothness. The etched surface is characterized by long rows of H-terminated silicon atoms. This structure is favored because it minimizes interadsorbate repulsion on the surface. A new technique for the analysis of surface infrared absorption spectra¹ is used to deconvolute the well-known vibrational spectrum of the etched H/Si(100) surface. This analysis yields a relatively simple picture of the structure of the etched surface -- a picture that is much simpler and much smoother than previous analyses. The significant effects of interadsorbate strain on the spectrum will also be discussed. Finally, the influence of gas evolution on the mesoscale roughness of etched surfaces will be discussed. Again, the fascinating patterns that form during etching yield new insights into the chemistry of etching.

¹I. T. Clark, B. S. Aldinger, A. Gupta, and M. A. Hines, J. Chem. Phys. 128, 144711 (2008).