Length measurement using a regular crystalline lattice and a dual tunnelling unit scanning tunnelling microscope in a thermo-stabilized cell

dThis paper describes length measurements using a regular crystalline lattice as a reference scale and a dual tunnelling unit scanning tunnelling microscope (DTU-STM) as a detector in a thermo-stabilized cell. Direct length comparisons between a certified standard scanning electron microscope (SEM) grating with an average pitch of 240 nm and a highly oriented pyrolytic graphite (HOPG) lattice spacing, which is 0.246 nm, were performed. Images of the grating and the HOPG were simultaneously obtained in the range of 1 mu m using the DTU-STM. The thermo-stabilized cell was developed to suppress any thermal drift error. In order to shorten the measurement time and thus reduce the thermal drift error, lengths of 1 mu m for the two samples were measured along the fast scanning axis. Rapid scanning, in which the tip speed was up to 1 mu m s(-1), was also utilized to shorten the measurement time. The grating pitch obtained by comparison with the HOPG lattice spacing agreed with that calibrated by the conventional diffraction method within an error of 2%.