Construction and evaluation of a traceable metrological scanning tunnelling microscope

Scanning tunnelling microscopy enables for imaging of conductive surfaces with a resolution down to the atomic level. However, virtually all commercial scanning tunnelling microscopes use piezo tube scanners and capacitance gauges what limits the operating range to typically less than 100 μm in the scanning axes and 10 μm in probing direction. Traceability of measured dimensions to the length unit metre can only be ensured by frequent calibration with the help of standards for pitch and step height. To improve the metrological characteristics of the measurement technique scanning tunnelling microscopy and to broaden its field of application, a directly traceable long range metrological scanning tunnelling microscope was set-up using a laser-interferometrically controlled nanopositioning unit with an operating range of 25 · 25 · 5 mm3 as scanner and a passive tunnelling current measuring probing system as a null indicator. Line scan repeatability of 5 nm has been achieved at 1 nm vertical resolution.