Spatially resolved materials modification using Helium Ion Microscopy

Helium Ion Microscopy (HIM) [1, 2] is best known for its high resolution imaging capabilities of both
conductive as well as insulating samples. However, since the introduction of Ne as an imaging gas for the
gas field ion source (GFIS) an increasing number of nano-fabrication applications are realized. While
the use of Neon as an imaging gas results in a somewhat lower lateral resolution (1.8 nm for 25 keV
Ne compared to 0.5 nm for 30 keV He) the user usually benefits from the much higher cross section for
nuclear stopping. The latter results in a larger number of sputtered atoms and bonds broken directly
by small impact parameter collisions.
After a brief introduction of the technique I will present results obtained using direct write milling low
fluence ion beam irradiation and ion beam based mixing. In all three cases the electronic or magnetic
properties of the target material will be altered at the nano-scale in a controlled way to achieve new
functionality. The examples comprise
∙ The fabrication of semiconducting graphene nano-ribbons by direct milling [3]
∙ The fabrication of a lateral spin valve structure using low fluence ion irradiation [4]
∙ The formation of individual 3 nm Si clusters for a room temperature single electron transistor [5]
For all presented examples the critical length scale of the nanostructure is smaller or in the range of
collision cascade. This size regime can not be accessed with traditional broad beam based ion irradiation
and holds many promises but also challenges that need to be overcome to enable new device concepts
and new functional materials on the nano-scale.
This work is supported by the European Union’s H-2020 research project ‘IONS4SET’ under Grant
Agreement No. 688072