Pressure-induced structural phase transformations in silicon nanowires

High-pressure structural behavior of silicon nanowires is investigated up to ∼ 22 GPa using angle dispersive X-ray diffraction measurements. Silicon nanowires transform from the cubic to the P-tin phase at 7.5-10.5 GPa, to the lmma phase at ∼ 14 GPa, and to the primitive hexagonal structure at ∼ 16.2 GPa. On complete release of pressure, it transforms to the metastable R8 phase. The observed sequence of phase transitions is the same as that of bulk silicon. Though the X-ray diffraction experiments do not reveal any size effect, the pressure dependence of Raman modes shows that the behavior of nanowires is in between that of the bulk crystal and porous Si.