A new method to fabricate metal tips for scanning probe microscopy

A new method to fabricate sharp metal tips on cantilevers for a scanning probe microscope (SPM) is presented in this paper. The metal tip film, which is deposited and patterned on a silicon mold with pyramidal etch pits, is attached by metal-to-metal bonding to a metal pad on a cantilever. Then a tip is fabricated on the cantilever by peeling the metal tip film off the mold at room temperature. Because the back side of the metal tip film becomes the tip surface, the tip surface is very smooth without grain boundaries associated with deposited thin films. A platinum tip with a radius curvature of less than 15 nm was successfully fabricated. In addition, the mold can be reused because the silicon mold is not dissolved during the tip fabrication. By applying this method in which the tip fabrication process is independent of the cantilever process, we succeeded to form a tip on various cantilevers. Moreover, we used the cantilever with the tip in a piezoresistive atomic force microscope and an atomic force microscope combined with a scanning tunneling microscope (AFM/STM) apparatus and obtained simultaneously high resolution topography and surface conductance images of a sample surface.