Optical microscopes were the first form of microscope to be designed and employed in scientific research, but their powers were quickly determined to be limited. The image got fuzzy or distorted while studying specimens smaller than the wavelength of the light.
The electron microscope, which employs electron beams to create an image of the material, was invented in 1921 to solve this constraint. The resolution of the microscopic images created was much improved as a result of this.
Scanning probe microscopy was invented in the late twentieth century to investigate surfaces with atomic resolution, which is impossible to do with an electron microscope. The first scanning tunneling microscope was invented in 1981 by Dr. Gerd Binnig and Dr. Heinrich Rohrer. This was an important development in nanotechnology since it allowed scientists to see an atomic-level representation of the surface of samples.
Scientists may now look at individual atoms, study their properties, and manipulate them to build new structures.
Scanning Probe Microscopy Types
Scanning probe microscopes come in a variety of shapes and sizes, including:
The van der Waals force between the tip and the specimen is measured using an atomic force microscope (AFM).
The electrical current between the tip and the specimen is measured using a scanning tunneling microscope (STM).
How does an SPM work?
A scanning probe microscope uses a cantilever with a sharp probe tip to scan the surface of the object. The tip goes back and forth in a highly precise manner, allowing the probe to be moved atom by atom.
When the tip of the cantilever approaches close to the surface of the sample, a force deflects the cantilever, which may be detected using a laser reflected from the cantilever into photodiodes. Deflections can be caused by a variety of forces, including mechanical, electrostatic, magnetic, chemical bonds, van der Waals, and capillary forces.
A computer combines the data from the laser reflections detected by the photodiodes to create an image. The image is colorless since it is a representation of attributes rather than light, though the computer program may add color to help distinguish the various qualities of the specimen.
SPM Techniques
Scanning probe microscopy employs a variety of approaches, depending on the study's goals.
The microscope could, for example, be adjusted to "contact mode," which entails a constant force between the cantilever tip and the specimen's surface. This mode enables for the quick creation of a surface image.
The microscope can also be adjusted to "dynamic mode," which includes oscillating the cantilever so that the tip intermittently taps the surface of the specimen. When the study sample has a soft surface, this is especially useful.