How do swift ions interact with matter? By penetrating into a material, they excite electrons, until they are abruptly stopped within the matter. A crystal can thus be heated locally by creating a cylindrical zone of "disorder" called latent trace. Under grazing incidence, the latent traces remain close to the surface and can therefore be easily shaped.
The swift ion irradiation of MoS2 or strontium titanate (SrTiO3) monocrystals leads to the formation of a series of aligned "bumps", which were reconstructed in simulations. The irradiation of an ultrathin MoS2 layer deposited on glass can actually create an incision in the layer. However the cutting and folding of the cutting edges can only occur if the trajectory of the ions is aligned along a crystallographic MoS2 axis. In the case of graphene, incisions and bends occur spontaneously regardless of ion beam orientation.
This work by CIMAP in Caen, France, was completed in collaboration with the University of Duisburg-Essen, Germany, Pennsylvania State University, USA, and the University of Vienna, Austria.