ALL TUNGSTEN AFM CANTILEVER WITH < 40 NANOMETRE PYRAMIDAL TIP

We develop wear resistant, electrically conducting AFM probes. Here, we describe a new AFM probe made entirely out of tungsten (W). The fabrication involves microfabrication techniques such as surface moulding, thin-film structuring of tungsten and high aspectratio SU-8 patterning. The metallic cantilever and tip are attached to a SU-8 photopolymer body. The free-standing 500-nm-thick cantilevers are obtained by a wafer-through etching. Figure 2 shows a SEM image of the SU-8 body with W cantilevers and a close-up of a W tip having a radius < 40 nm. The 200-μm-thick SU-8 body is 1.8 x 3.2 mm. Cantilever resonance frequencies range between 35 kHz and 1 MHz as measured by optical interferometry, which corresponds well to theoretical values assuming Ew= 410 MPa, ρw= 19.3 g/cm3. The AFM probes have been designed for conducting mode imaging at the nanoscale whereas W has been chosen for its excellent properties in electrical conductivity and wear. First characterisation has demonstrated AFM imaging capability.