Atomic Force Microscope Principles

Study Notes

Principle of AFM

Atomic Force Microscopy (AFM) operates on the principle of measuring forces between a sharp probe and a sample surface at the nanoscale.
It utilizes a cantilever with a sharp tip that reacts to surface forces, allowing for high-resolution topographical imaging.

Tip Characteristics

The sharp tip used in AFM typically has a diameter in the range of a few nanometers.

Generation of Topographical Maps

A three-dimensional topographical map in AFM is generated by scanning the probe across the sample surface while measuring the cantilever's deflection.
The data collected from deflections are converted into a height information, creating detailed surface maps.

Resolution Comparison

AFM achieves resolution at the atomic level, providing finer detail than radiation-based microscopy techniques which are limited by diffraction.

Sample Movement

AFM may utilize either sample movement or probe movement for scanning, differing from techniques where samples are often fixed or imaged through lens adjustments.

Deflection Tracking

The most common method to track deflection in scanning probe microscopes is through optical beam deflection, where a laser beam reflects off the cantilever onto a photodetector.

Cantilever Coating Benefits

Coating the cantilever's back with gold or another metal enhances its reflective properties, improving the accuracy of laser deflection measurements.

Scanning Stage Purpose

The scanning stage in an AFM setup serves to precisely control the movement of the sample relative to the probe, ensuring accurate measurements.

Composition of Scanning Probe

The scanning probe typically consists of a cantilever with a sharp tip made from materials like silicon or silicon nitride.

Detection Techniques

Techniques not mentioned in the AFM detection system include methods such as electron beam detectors or other imaging methods that do not leverage probe-based interaction.

Description

Learn about the principles of Atomic Force Microscope (AFM) which is based on the cantilever principle and uses a sharp tip to scan surfaces with feedback mechanisms. Understand how the force exerted by the tip on the sample is measured by following the cantilever’s deflection.