Manipulating the morphology of colloidal particles via ion beam irradiation: A route to anisotropic shaping

Ion beam irradiation of spherical colloidal particles is a viable route to induce particle deformation, especially to get anisotropic shapes. Even though less common in comparison with dry etching techniques, different types of morphological changes can be attained depending on the process parameters (angle of incidence, energy, fluence of the ion beam, type of ion, temperature) and on particle material and initial particle arrangement (crystalline or disordered, made up of isolated or closely-packed particles). The technique can be harnessed to get anisotropic deformation of spherical colloidal particles into an ellipsoidal shape, but also to tailor the interstices between closely-packed colloidal particles, to get particle necking and coalescence as well as particle rearrangement. As such, particle deformation based on ion irradiation can find diverse applications from synthesis of ellipsoidal particles to modified templates for colloidal lithography. In this review, we examine in detail the principles and models of colloidal particle shaping via ion beam irradiation, the influence of process parameters on particle morphology and the applications of irradiated particles.