Direct assembly of nanowires by electron beam-induced dielectrophoresis

Controllable self-assembly is an important tool to investigate interactions between nanoscale objects.Here we present an assembly strategy based on 3D aligned silicon nanowires.By illuminating the tips of nanowires locally by a focused electron beam, an attractive dielectrophoretic force can be induced, leading to elastic deformations and sticking between adjacent nanowires.The whole process is performed feasibly inside a vacuum environment free from capillary or hydrodynamic forces.Assembly mechanisms are discussed for nanowires in both one and two layers, and various ordered organizations are presented.With the help of moisture treatment, a hierarchical assembly can also be achieved.Notably, an unsynchronized assembly is observed in two layers of nanowires.This study helps with a better understanding of nanoscale sticking phenomena and electrostatic actuations in nanoelectromechanical systems, besides, it also provides possibilities to probe quantum effects like Casimir forces and phonon heat transport in a vacuum gap.