Speaker: Gaurav Nanda (Kavli Nanolab Delft)
Subject: Nanofabrication with Helium Ion Microscope: Modification of Graphene and Growth of 3D AFM Probes
Location: Faculty of Applied Sciences, TU Delft
Date: Tuesday, September 15 2015, 13:00-14:00
Usually speakers from outside the university come to present their work during the Technology Colloqia of the Kavli Nanolab, but now a PhD student presented to the people of his own faculty. The topic of today was the helium ion microscope and mostly its current applications. Given that this type of talk is part of the Technical Colloqia series, it focuses on the technical aspects of the research mostly, and not experimental results.
In brief, the helium ion microscope contains a tip with three atoms that are slightly apart. The tip is slightly turned to select the current from the brightest atom. Neutral gas atoms close to this tip (atom) will be ionized through the process of electron tunneling. Several accelerating ions will form a beam that is focused onto the sample. An advantages of using this technique is much deeper penetration and a 0.5nm resolution.
One of the applications of this helium ion microscope is the growth of specific 3D AFM tips. Take into your mind a surface on which we wish to create a needle that could be used to feel surfaces like an AFM. In this technique, a gas is brought around this surface. Then, the helium ion beam can be used to accurately ‘glue’ these gas molecules into a needle by constantly shining at the desired position. In this way, tips of the desired geometry can be produced with high precision. Some of the current drawbacks of this technique is fragility of the thin tip (~30 nm) and its ‘stickiness’ to some surfaces.