Orz_STM

Scanning Tunneling Microscope STM (Scanning Tunneling Microscope), through the quantum tunneling effect, uses conductive micro-probes to obtain atomic-level resolution on the sample surface.

The basic principles are as follows:

The microcontroller scans the tip in a raster pattern by generating X and Y scan signals using a DAC. A DC bias voltage, also generated by the DAC, is applied to the conductive sample, causing electrons to pass through the gap between the tip and sample when they are close enough (<1 nm). This current is measured by a preamplifier, which outputs a voltage proportional to the tunneling current. This signal is digitized and fed into the PI control loop, the output of which is sent to the DAC and used to drive the Z-axis of the scan head, allowing the tip to track the sample topography. As the tip approaches the sample surface, the tunneling current increases exponentially with decreasing distance (approximately a factor of 10 per Angstrom)

This project aims to use raw materials that are as easy to obtain as possible in daily life to verify the principle and conduct qualitative analysis, hoping to obtain a resolution of 10~10²nm level.

The basic block diagram is as follows:

The main parts of the project include:

1. Scan head, displacement actuator and mechanical bracket part

The bracket and displacement coarse adjustment system are as shown below (including CNC machined parts and some standard parts):

Some progress on scanning probes:

iron wire

tin

Tin (cut off)

Extra sharp pen tips for comparison:

Small utility knife tip for comparison:

2. Acquisition and drive circuit (ADC/DAC/Step Controller)

Ultra-low ripple output power supply board:

Analog acquisition and displacement voltage output board:

Front-end amplifier board:

3. Microcontroller

(pending upgrade...)

4. PC software

(pending upgrade...)

Note: (See attachments for PCB renderings of each part)