Atomic force microscope tip sharpening and evaluation by electric field confinement using a metal grid close to the tip

By setting a metal grid close to a Si tip on an atomic force microscope (AFM) cantilever and applying voltage between the grid and the tip, electrons were field emitted from the tip apex, where a high electric field was induced confining the metal grid. The pattern of field-emitted electrons was projected at high magnification by a shadow of the grid onto the phosphor screen of a field emission microscope (FEM). The FEM image shows the tip radius and the cleanliness. The confined electric field was also used to sharpen the tip by a thermal-field (TF) treatment, in which the tip is heated under a high electric field. The change in the FEM images before and after the treatment is reported, and the faceting of the Si tip apex by the treatment is discussed. The noncontact-AFM image of Si(111) 7 x 7 with atomic resolution was observed with the TF treated tip immediately after the tip came near to the sample. (C) 2000 American Vacuum Society. [S0734-211X(00)00302-4].