Aangstrom is a low-cost scanning tunneling microscope developed as an undergraduate engineering project at Northwestern University. It was designed around a target hardware cost of approximately US$300 and combines a stepper-driven coarse positioning stage, a quadrant unimorph piezoelectric scanner, a tunneling-current transimpedance amplifier, control electronics, and a dedicated power-supply board. The three-motor coarse stage architecture provides coarse approach and orientation adjustment, while the piezoelectric scanner enables fine three-dimensional tip motion. The electronics support tunneling-current acquisition, programmable sample bias, piezoelectric actuation, and constant-current feedback. The instrument produced periodic atomic-scale contrast on highly oriented pyrolytic graphite (HOPG) under ambient conditions. We also include provisions for AC-bias excitation; these should not be interpreted as a validated differential-conductance spectroscopy capability. Repository Contents: CompleteAssembly: The complete SolidWorks assembly of the microscope, including the mechanical integration of the scan head and associated components. The principal file is Full_Assembly.SLDASM, which provides the overall assembly model. Scan Head: Mechanical design files for the custom scanning head and coarse positioning mechanism. The folder includes SolidWorks parts and assemblies, STEP models, a DXF file, and a technical drawing. The design incorporates three stepper-driven fine-pitch screws and the quadrant unimorph scanner, with models for the motor, screw, scanner mount, and supporting mechanical components. Tunneling_Amp: KiCad design files for the custom tunneling-current transimpedance amplifier. The folder contains the schematic, PCB layout, KiCad project, Gerber manufacturing files, and development-related files. The amplifier uses an OPA928-based front end with a nominal 100 MΩ feedback resistance for low-current measurement. Mainboard: KiCad project files for the mixed-signal control board. The design includes separate schematic sheets for ADC acquisition, DAC generation, piezoelectric drivers, stepper-motor drivers, voltage reference, power distribution, and connectors. The folder also contains the PCB layout, component/BOM files, and a STEP model of the board. Power_Supply: Design and manufacturing files for the dedicated analog and digital power-supply board. The folder includes KiCad schematics and PCB layouts, Gerber files, BOM materials, CAD models, plots, and SPICE simulation files. Vibration Isolation: SolidWorks and STEP models for the microscope's mechanical isolation assembly, including plates, springs, structural supports, O-ring components, and related hardware. Firmware — Source code and development files for the instrument's embedded control software. The archive includes Teensy controller code, ESP32-related files (for a web-based interface), PC software, stepper testing, and additional STM software...
Built with the Forest WIki.
User contributed content is licensed under a
Creative Commons CC By 4.0 License.