Fast and precise electrostatic beam position control for an atomic-resolution STEM

C55-10b-270389Recent developments in electron microscopes, especially improved optics and new detectors have led to new types of experiments in the fields of physics, quantum information, and biology. With all the recent progress, one key system of the microscope, the scanning system, has fallen behind. The proposed development will introduce a fundamentally new type of scanning system that replaces slow electromagnetic scans with faster, more precise, electrostatic scanning. The capabilities of the scanning transmission electron microscope (STEM) have expanded tremendously in recent years, to the point that individual atom’s identity and lattice dynamics can now be probed by electron energy loss spectroscopy (EELS). These capabilities are enabled and accelerated by technical developments in aberration correction, electron detectors, monochromators, spectrometers, and open-source software. Throughout this renaissance, the scanning system itself – a key component of every STEM - has remained relatively constant. To overcome the current limitations, a fundamentally new approach is required—replacing slow electromagnetic scan coils with electrostatic scanning. Phase I work will consist of proof-of- principle experiments and calculations leading toward the design of a practical, marketable electrostatic scanning system for STEM for building in Phase II. In Phase I, a prototype electrostatic scan system will be designed, built, and tested. The results will inform design decisions for Phase II in each of three key areas: (1) deflector hardware— prototype electrostatic deflector plates will be mounted on the column to assess the temporal response (MHz-GHz), induced aberrations, and effect of instabilities. (2) fast control electronics—existing electromagnetic scan control electronics will be extensively modified to enable electrostatic scanning for testing low noise deflection voltages over a wide range of magnifications at high speed. (3) software—to match the hardware capabilities and with architecture and API providing advanced users access to arbitrary scans quickly and efficiently. The proposed development will enable new types of experiments for researchers around the world who invest in this technology and generate a marketable unique upgrade product for the only US-based electron microscope manufacturer, leading to more jobs in Washington state.