An ultra-precision scanning tunneling microscope Z-scanner for surface profile measurement of large amplitude micro-structures

This paper presents an ultra-precision STM Z-scanner for surface profile measurement of micro-structures with large amplitudes on the order of several tens of micrometers. The Z-scanner consists of an STM probe, a long stroke PZT actuator with a full stroke of 70 mu m, and a linear encoder. The linear encoder is employed to accurately measure a Z-directional displacement of a STM probe tracking a sample surface. The linear encoder yields a least significant bit resolution of 0.5 nm over the full stroke of the actuator. The peak-to-valley value of the Z-scanner nonlinearity is smaller than 10 nm over an effective measurement range of 50 mu m. Experiments of surface profile measurement of samples with micro-structures were carried out by combining the Z-scanner and an X-directional PZT scanning stage, on which the sample is mounted. The feasibility of the developed ultra-precision Z-scanner has been confirmed from the measurement results.