STM Topographic Imaging Lab: Constant-Current vs…

What is Scanning Tunneling Microscopy (STM)?

Scanning tunneling microscopy (STM) is a powerful tool for imaging surfaces at the atomic scale. It operates by scanning a sharp metal tip over the surface of a conductive sample, measuring the tunneling current between the tip and the sample as a function of position.

The STM technique relies on quantum mechanical tunneling, where electrons can pass through the insulating gap between the tip and the sample due to their wave-like nature.

Constant-Current Mode vs Constant-Height Mode

In constant-current mode, the feedback system adjusts the tip-sample distance to maintain a fixed tunneling current. This approach is useful for imaging surfaces with varying heights but can lead to artifacts due to changes in the local density of states.

Conversely, constant-height mode keeps the tip at a fixed height above the surface and varies the current to maintain this position, which helps in reducing these artifacts and providing clearer images.

live demo · related simulation● LIVE

Reciprocal-Lattice Cosine-Sum Surface Synthesis

The reciprocal-lattice cosine-sum method is used to synthesize surfaces from STM data. It involves a Fourier transform of the measured current distribution, which can then be inverted to reconstruct the surface height profile.

This technique allows for accurate reconstruction and analysis of complex surface structures at the atomic level.

Live Cross-Section Comparison

The live cross-section comparison feature in the STM Topographic Imaging Lab allows users to visualize the reconstructed surface heights alongside the true surface, providing a direct comparison between the two modes.

This helps in understanding how each mode affects the final image and aids in optimizing imaging parameters.

Frequently asked questions

What is quantum mechanical tunneling?

Quantum mechanical tunneling refers to the phenomenon where particles can pass through a potential barrier that they classically shouldn't be able to, due to their wave-like properties.

Why are artifacts common in constant-current mode imaging?

Artifacts arise because the feedback system adjusts for changes in the local density of states, which can vary with surface features. This adjustment can lead to distortions in the image.

How does the tip-sample distance affect STM images?

The tip-sample distance is crucial as it directly influences the tunneling current and thus the quality of the image. A consistent distance helps in obtaining accurate surface reconstructions.

What are the benefits of using constant-height mode over constant-current mode?

Constant-height mode reduces artifacts by maintaining a fixed tip-sample distance, providing clearer images that better reflect the true surface structure without feedback-induced distortions.

Try it live

Everything above runs in your browser — open STM Topographic Imaging Lab: Constant-Current vs Constant-Height (2D) and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.

▶ Open STM Topographic Imaging Lab: Constant-Current vs Constant-Height (2D) simulation