Electron beam mediated bending and adhesion driven bundling of GaAs nanowire

It is commonly accepted that the control over NW orientation is reached through growth conditions [1]. Less recognized is that NW orientation may be post-growth-influenced by other factors. We report here the results on GaAs NWs, grown vertically aligned but subsequently driven to self-assembly. The self-assembly phenomenon has been rarely reported for GaAs NWs [2] as well as for ZnO NWs and nanorods [3, 4]. The research work on the topic has been mainly directed towards determining the nature of the driving force responsible for the NWs bending, while little effort has been dedicated in understanding the coupled bundling effect. We will elucidate the rising of NWs clusters into the framework of the studies on adhesion, friction, and compliance properties of natural and bio-mimetic contact surfaces [5]. We have successfully interpreted the NWs bundling in the framework of the theoretical model and the experimental check performed by means of poly(dimethylsiloxane) (PDMS) fibrillar (micro/nano-pillars) arrays [6]. The mechanical and surface properties of the NWs together with the geometrical design of the arrays play a key role in the realization of VA NW arrays. However, the same parameters open to the appealing chance of locally engineering NW arrays in micro- and macro-patterns, so that the electron beam-mediated bending coupled to adhesion-induced bundling of GaAs NWs may be turned into an operative procedure for the selective fabrication and control of NW integration in devices at the nanoscale [2]. [1] S. A. Fortuna et al., Semicond. Sci. Technol., 25, 024005 (2010). [2] Xing, D. et al., Nano Lett., 11, 4947–4952 (2011). [3] X. Wang et al., Applied Physics Letters, 86, 013111 (2005). [4] J. Liu et al., Nanotechnology, 19, 185607 (2008). [5] A. Jagota, Materials Science and Engineering, R 72, 253–292 (2011). [6] N. J. Glassmaker et al., J. R. Soc. Interface, 1, 23–33 (2004).