Comparative studies of hydrogen termination on single-crystal silicon surfaces by FT-IR and contact-angle measurements

The hydrogen termination process on a Si(100) surface has been studied by multiple internal reflection infrared spectroscopy (MIR-IS) and contact-angle measurements. Three main silicon hydride absorption peaks at 2087, 2104, and 2114 cm(-1) were found to gradually increase with the hydrofluoric (HF) acid etching. Eventually, a constant peak height was reached as an indication of complete hydrogen termination. Integration of all the surface hydrides absorption peaks (2000 to 2200 cm(-1)) provides direct quantitative evaluation of the hydrogen termination process. On the other hand, water contact-angle data were shown to consistently lag behind the IR measurement in determining the extent of hydrogen termination on the silicon surface. Analysis of the surface free energy of HF-etched silicon surfaces indicates that the degree of the hydrogen termination determined by water contact-angle measurements is subjected to inaccuracies due to the preferential hydrogen-bonding interaction between the water and silicon surface oxide.