Tip production technique to form ferromagnetic nanodots

Application of the ion-shadow sputter technique is proposed to produce tips used for the study of point contact as well as for scanning tunneling microscopy (STM). It is a sputtering technique using powders with low sputtering rate as the mask material. By this method, sharp and long tips could be produced for Si, Au, Fe, permalloy and invar. The tip length is typically more than 15 μm, and the radius of curvature is about 10–20 nm or less. Furthermore, a nonmagnetic tip (e.g., Si) capped with a magnetic apex (300 nm Fe) has been produced. This type of tip is clearly useful for STM experiments in transmission electron microscopy (TEM).