Open STM: A low-cost scanning tunneling microscope with a fast approach method
Description
In this paper, we have designed a low-cost scanning tunneling microscope (STM) priced at 300 USD or 2000 CNY. This microscope is suitable for educational purposes and low-demand research imaging at the nanometer level. This microscope's motion components and scanner are controlled using piezoelectric materials, avoiding the thermal drift associated with traditional motor control. Our tip approach algorithm, which considers the capacitance and friction characteristics during piezoelectric slider movement, has reduced the time required for sample loading to establish tunneling current to approximately 1 minute. The dimensions of the microscope body are 45×45×31.5mm(W ×L×H), and the control voltage does not exceed 15V, ensuring the safety of operators with limited experience. In the performance verification, we performed a scanning tunneling scan on a Highly Oriented Pyrolytic Graphite(HOPG) sample with bias voltages of 50mV and 60mV, resulting in clear observations of the atomic features of HOPG in the STM pattern. • 3D Models The STM body is predominantly manufactured through CNC machining of aluminum blocks. A total of 7 components need to be machined. We provide the original Solidworks design and STEP files for manufacturing in this folder. Drill information is documented in the corresponding PDF files. • PCB The STM includes eight PCBs, three utilized for the microscope's control unit, one for the pre-amplifier, and four for circuitry interconnection. The PCBs were designed using EasyEDA(Or JLC EDA in China), and this folder includes project files, schematics, and Gerber files for PCB manufacturing. • HardwareCode The central controller for the circuit control section employs the ESP32-WROOM-32E-N8 microcontroller module. This folder contains the microcontroller firmware and source code (written using the ESP-IDF framework with PlatformIO). • PythonScript This folder includes supervisory software written in Python. Install the libraries(with specific versions) and launch the software by running “launch.bat” or via the command line “python main.py”. All software source code(/PythonScript) is licensed under GPLv3. (https://www.gnu.org/licenses/gpl-3.0.en.html) Everything else is licensed under CC-BY-SA-4.0. (https://creativecommons.org/licenses/by-sa/4.0)