Hydrogen-terminated silicon surface
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A hydrogen-terminated silicon surface is a chemically passivated silicon substrate whose native oxide (SiO2) thin film is removed by etching in hydrogen fluoride aqueous solution, leaving the surface silicon atoms covalently bonded to hydrogen.
Since all surface Si atoms are fully co-ordinated, hydrogen termination leads to enhanced stability in ambient environments unlike a 'clean surface' having unpassivated surface atoms, or dangling bonds. It is so inert that it can be handled in the air without any special care for several minutes.
A hydrogen-terminated silicon surface has another excellent property: it can be flattened at the atomic level by etching. For example, to etch a hydrogen-terminated silicon(111) surface, ammonium fluoride aqueous solution or boiling water is usually used.
Like other silyl groups of organic compounds, the H-Si groups on the surface react with molecules that have terminal unsaturated bonds or diazo groups. The reaction is called hydrosilylation. Many kinds of organic compounds with various functions can be introduced onto the silicon surface by the hydrosilylation of a hydrogen-terminated surface.
Silicon is the Earth's second most abundant chemical element, and today high-purity silicon crystals are mass-produced. Consequently, hydrogen-terminated silicon surfaces are a promising material as a compound of organic and inorganic substances.
