We can see atoms! Scanning Tunneling Microscope
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Full video: • What Is An Atom And How Do We Know?
A scanning tunneling microscope (STM) is a powerful tool used in surface science that allows researchers to visualize and manipulate atoms and molecules at the surface level with remarkable precision. The ability of an STM to "see" atoms is rooted in the principles of quantum mechanics, specifically the quantum tunneling effect.
Here's a brief overview of how it works:
1. Sharp Tip: The STM has an extremely sharp conducting tip, usually made of tungsten or platinum-iridium, that is brought very close (about a nanometer) to the surface of the conductive or semi-conductive sample being examined.
2. Voltage Application: A voltage is applied between the tip and the sample, creating an electric field. The tip does not physically touch the surface of the sample.
3. Tunneling Current: Due to the close proximity of the tip to the sample, electrons can tunnel through the vacuum between the tip and the surface. This phenomenon is known as quantum tunneling. The probability of tunneling, and thus the tunneling current, is highly dependent on the distance between the tip and the surface atoms.
4. Current Measurement: As the tip scans across the surface, it maintains a constant height by adjusting its position to keep the tunneling current constant. Changes in current are detected and used to map the surface topography at atomic scales.
Visualization:
The STM does not create images of atoms in the conventional sense (like a camera). Instead, it measures the tunneling current which varies with the atomic configuration of the surface. By scanning the tip across the surface and recording variations in the tunneling current, the STM constructs a detailed map of the surface at the atomic level.
Resolution and Applications:
The resolution of an STM is so high that it can differentiate between individual atoms and even provide information about the electronic states of atoms and molecules. This capability makes it an invaluable tool in fields like materials science, nanotechnology, and condensed matter physics.
By exploiting the principles of quantum tunneling, scanning tunneling microscopes provide a direct and highly detailed view of atomic and molecular structures on surfaces, enabling scientists to study materials with unprecedented precision and depth.
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