What is an atomic force microscope
Atomic Force Microscopy: A new experimental technique that uses the interaction forces between atoms and molecules to observe microscopic features on the surface of an object. It consists of a nanometre-sized probe fixed to a sensitively manipulated micron-sized flexible cantilever. When the probe is very close to the sample, the forces between the atoms at its tip and the atoms on the sample surface cause the cantilever to bend away from its original position. A three-dimensional image is reconstructed from the amount of deviation or frequency of vibration of the probe as it scans the sample. It is possible to indirectly obtain the topography or atomic composition of the sample surface.
It is used to study the surface structure and properties of substances by detecting the very weak interatomic interaction forces between the surface of the sample to be measured and a miniature force-sensitive element. A pair of micro-cantilevers, which are extremely sensitive to weak forces, are fixed at one end, and a tiny tip at the other end is brought close to the sample, which then interacts with it, and the forces cause the micro-cantilevers to deform or change their state of motion.
When scanning the sample, the sensor detects these changes and obtains information on the distribution of the forces, thus obtaining information on the surface structure with nanoscale resolution. It consists of a microcantilever with a needle tip, a microcantilever motion detection device, a feedback loop to monitor its motion, a piezoelectric ceramic scanning device to scan the sample, and a computer-controlled image acquisition, display and processing system. Microcantilever motion can be detected by electrical methods such as tunnel current detection or optical methods such as beam deflection and interferometry, etc. When the tip of the needle and the sample are sufficiently close to each other and there is a short-range mutual repulsion between them, the repulsion can be detected to obtain the surface of the atomic level of resolution of the image, and in general the resolution of the nanometre level.AFM measurements of samples have no special requirements, and can be used to measure the surface of solids and adsorption systems.
