Current displacement (I-Z) spectroscopy-based characterization of nanoscale electro machining (nano-EM) tools

A nanoscale die-sinking electro machining (nano-EM) process has been developed on the scanning tunnelling microscope (STM) platform. The consistency of the features machined by the process depends on the quality of the tools used. A simple, fast, and reliable method has been developed using in situ STM to characterize nano-EM tool quality using current displacement (I-Z) spectroscopy curves. The tunnelling current from the tool was monitored as a function of the distance from the workpiece. The distance where the tunnelling current dropped to zero was correlated with the tool's ability to perform nano-EM and atomic resolution surface scans. The tools for which the tunnelling current dropped to zero at 4 Å from the workpiece resulted in consistent nano-EM and atomic resolution topographic scans. A quality criterion based on the I-Z method has been developed for nano-EM tools. This criterion can be extended to define the tool quality in probe-based machining processes and in the emerging field of molecular electronics.