Figure 4: Sharpening of a hafnium diboride probe.
From: Field-directed sputter sharpening for tailored probe materials and atomic-scale lithography
(a) A schematic representation of the probe growth procedure. An ECE tungsten tip is sharpened by FDSS and a film of amorphous hafnium diboride is grown. The hafnium diboride film is then sharpened by FDSS to bring the tip to its final form. (b) The tip following deposition of a nominal 70 nm amorphous hafnium diboride film. The tip exhibits a radius of curvature of 75 nm and a conformal HfB2 coating. Scale bar, 100 nm. (c) After sharpening (1.2 keV ion energy, Vr=0.167, 60 min) the radius of curvature is reduced to 4 nm. Scale bar, 20 nm. (d) As a control, the tip is further sputtered under CSE conditions (1.0 keV ion energy, Vr=0, 20 min). The probe radius increases to 13 nm and the surface exhibits increased roughness and reduced symmetry. Scale bar, 20 nm.
