Intrinsic twisting instability of kinked silicon nanowires for intracellular recording.

A kinked silicon nanowire (KSiNW) is a zigzag-shaped nanowire with its growth direction changing regularly at the kinking joints, resulting in a quasi-two-dimensional structure. An intrinsic tendency for the two-dimensional system is to generate some out-of-plane vibrations to withstand the mechanical instability in the third dimension. In the present work, we report a lattice dynamical study of the intrinsic out-of-plane twisting vibration of KSiNWs. We derive the dynamical matrix analytically, and explore the kinking effect on the phonon spectrum of the KSiNWs. Based on lattice dynamical analysis, we obtain an analytical formula for the geometrical dependence of the twisting amplitude of the KSiNWs. The analytical formula provides valuable information on the kinking induced twisting stability of KSiNWs serving as bio-probes for intracellular recording application.