Design and Construct of a High-Precision and Long-Stroke AFM Probe-Unit Integrated with a Linear Encoder

This paper presents a high-precision and long-stroke AFM probe-unit for measurement of large area micro-structured surfaces. The probe-unit consists of a silicon cantilever and a pre-loaded piezoelectric (PZT) ring actuator with a stroke of 70 μm along the Z-axis. A small linear encoder with nanometer resolution is integrated in the PZT actuator for measuring the displacement of the PZT actuator. The encoder scale is aligned along the axis of motion (Z-axis) of the ac- tuator to avoid the Abbe error. The linear encoder makes the AFM probe-unit to have a resolution of 1 nm over the full stroke of the PZT actuator. The AFM probe-unit is combined with two linear stages, which are used for scanning the sample in the X- and Y-directions over an area of 50 mm (X)× 40 mm (Y). Displacements of the X- and Y-stages are measured by linear encoders with nanometer resolution. Measurement experiments of a sinusoidal micro-structured surface are carried out.