Magnetic/fluid-bearing stage for atomic-scale motion control (the angstrom stage)

This paper describes a magnetically suspended six-degree-of-freedom precision motion control stage with subnanometer positioning noise inside a 100-mu m cube of travel. This stage utilizes multiple electromagnetic actuators and capacitance probes to provide control forces and position feedback, respectively. The suspended platen (3-kg mass) is floated in oil to enhance the performance of the magnetic bearings. The stage has been designed for use as a sample positioning stage for scanning tunneling microscopy (STM). Images obtained by STM show that the stage has a positioning noise of less than 0.2 nm peak-to-peak over 5 seconds, while the capacitance probes (used for position feedback) indicate a positioning noise less than 0.1 nm peak-to-peak. We present several STM images and the step-following response for a 0.1 nm step input in order to demonstrate the utility of this stage as a new concept for precision motion control.