Silicon wafers can be etched in hydrofluoric acid (HF) to remove the native oxide and form a hydrogen-terminated silicon surface. The hydrogen-terminated surfaces undergo hydrosilation with unsaturated compounds (such as terminal alkenes and alkynes), to form a stable monolayer on the surface. For example:
:Si-H + HC=CH(CH)CH → Si-CHCHH-(CH)CH
The hydrosilylation reaction can be initiated with UV light at room temperature or with heat (typical reaction temperature 120-200 °C), under moisture- and oxygen-free conditions. The resulting monolayer, which is stable and inert, inhibits oxidation of the base silicon layer, relevant to various device applications.