Smart nano-machining and measurement system with semiconductive diamond probe

We have developed an ultraprecision machining system with an in situ STM function. For this purpose, we have made a semiconductive diamond probe of sufficient hardness to prevent deformation or damage occurring during machining and with a tunnel-current-detecting capability for the fabrication of three-dimensional nano-structures in any material, independent of hardness. In order to realize this system, we first constructed a high-resolution driving system with two single-tube three-dimensional piezoelectric devices as scanners. Test measurements with a conventional tungsten probe showed that this driving system could obtain STM images with a resolution of about 20 nm. Next, we developed a CVD molding technique for fabrication of the semiconductive diamond probe. A mold with a 70 µm×70 µm square pyramidal pit was formed by anisotropic etching of (001)Si in potassium hydroxide (KOH) solution. Then, a semiconductive diamond thin film was deposited onto the pyramidal mold using hot-filament CVD. After removing the mold by wet etching, the resulting pyramidal diamond probe had a facial angle of 70.6° and a tip radius of about 70 nm. In order to test the applicability of this semiconductive diamond probe, we machined polished Si (a typical hard-to-cut material) to form nano-scale grooves and square recesses, and then measured those machined structures in situ using the three-dimensional driving system. The results showed that this newly developed semiconductive diamond probe was effective both as a machining tool and as an STM probe.