What is the Scanning Tunneling Microscope (STM) Project?
Scanning Tunneling Microscopes, otherwise known as STMs, are used in analyzing the atomic structure of conductive materials, and it is a great tool for understanding material properties. The problem is that commercial STMs can cost upwards of $10,000 which is what our project aims to solve; creating a cost-effective STM allows for more people to have access to technology that allows us to see the foundation of our world and start to understand it better.
What are the project requirements?
Requirements of our STM are that it is cost-effective, serviceable, and well documented in order to create a user-friendly experience. Along with the functional requirements of creating an STM that is able to provide accurate, low-noise, and high-resolution measurements.
Commercial STM Examples
Commercial STMs use different components like piezoelectric tubes and proprietary feedback systems to achieve granular imaging with the drawback of requiring extra heavy equipment like power supplies and being far more costly.
Examples include:
Nanosurf's NaioSTM
ScientaOmicron's STM
STM Concept
There are 5 main modules to our STM, the STM tip, preamp, microcontroller, digital to analog converter, and piezoelectric disc.
STM Tip
Using an atomically sharpened tungsten tip, we apply a charge between the tip and scanning surface and can read a tunneling current that changes exponentially as it goes over atomic bonds.
Preamp
The tunneling current from the tip is in the range of nano amps which cannot be read by our MCU. To solve this, we use a transimpedance amplifier to take in nA and output an amplified signal in volts.
Microcontroller (MCU)
To compile an image, we will collect 65,536 data points which we will read with an Arduino and output to a computer for further plotting. Additionally, the Arduino will be used to send signals to the DAC to control the scan.
Ditial-Analog Converter (DAC)
The DAC will take signals from the Arduino and will output a voltage to the piezoelectric disc to flex and control the scan.
Piezoelectric Disc
Piezoelectric devices take electrical energy and turn it into mechanical flex. The flex of our disc will drive the movement of our scan head, allowing us to take images.