Ion beam induced alignment of semiconductor nanowires

Epitaxially grown GaAs nanowires were irradiated with different kinds of energetic ions. The growth substrates were <100> GaAs, and the nanowires grow under an angle of 35 circle. A bending of the nanowires was observed under ion beam irradiation, where the direction and magnitude of the bending depends on the energy, the species, and fluence of the incident ions. By choosing suitable ion beam parameters the nanowires could be realigned towards the ion beam direction. In order to understand the underlying mechanisms, computer simulations of the ion irradiation were done using a special version of TRIM which accounts for the geometry of the nanowires. The simulated distributions indicate vacancy and interstitial formation within the implantation cascade as the key mechanism for bending.