Question

atomic force microscopy,its principal, resolution and use

Answer 1

What is AFM? The atomic force microscope (AFM) is one kind of scanning probe microscopes (SPM). SPMs are designed to measure local properties, such as height, friction, magnetism, with a probe. To acquire an image, the SPM raster-scans the probe over a small area of the sample, measuring the local property simultaneously

Principle of AFM

Both AFM and light microscope amplify the image of the sample but the major difference between them is that the former does not
use visible light; instead it uses a cantilever made from silicon or
silicon nitride having a very low spring constant to image a
sample. At one end of the cantilever, a very sharp tip (around 100–
200m long and 20–60 nm radius of curvature) is fabricated using
semiconductor processing techniques. The cantilever scans above
the surface of the sample by progressively moving backward and
forward across the surface. A piezo-electric crystal raises or
lowers the cantilever to maintain a constant bending of the cantilever. The force exerted on the tip varies with the difference in the
surface height and thus leads to the bending of the cantilever. A
laser beam gets constantly reflected from the top of the cantilever
towards a position-sensitive photodetector consisting of four sideby-side photodiodes (Figure 3). This laser beam detects the bend
occurring in the cantilever and calculates the actual position of the
cantilever. Thus, AFM records a three-dimensional image of the
surface topography of the sample under a constant applied force
(as low as nano Newton range), which provides a maximum
resolution image without causing any damage to the sample
surface.

Resolution

For AM-AFM the resolution in Z-axis should be in order of Angstroms under certain conditions. However it depends also on the material of the sample. Lateral resolution is much higher, around 10 nm.

Use

Compound semiconductor: Imaging compound semiconductor surfaces on atomic scale.
• Electronic materials: AFM tip is used to write and erase nanoscale electronic structures.
• Data storage: AFM is nowadays used for data storage due to space and cost constraints.
• Life science: AFM measures surface structures of various biological substances, and is capable of
visualizing biological objects from living cells down to single molecule levels.
• Pharmaceuticals: In pharmaceutical industries, AFM is used for drug crystallization study, particle
characterization and tablet coatings.
• Semiconductor: AFM is used in characterizing semiconductors.
• Optics: AFM is used in optics for the metrological measurement, since the optical profilers are unable to
image transparent specimens.
• Polymers: Polymers are generally insulators. High resolution images of the polymers are very difficult to
obtain using SEM/TEM, as the samples need to be coated with a conductive layer. AFM however can
generate images of polymers without sample preparation.

Answer 2

Atomic force microscopy (AFM) is a type of scanning probe microscopy that allows for the imaging and manipulation of materials at the atomic and molecular scale. The principal of AFM is based on the interaction between a sharp probe tip and the sample surface. As the tip scans across the surface, a small force is detected between the tip and the surface, which is used to construct an image of the surface topography.

The resolution of AFM depends on the size and shape of the probe tip. The typical resolution for AFM is on the order of a few nanometers, making it an extremely powerful tool for imaging and analyzing the surfaces of materials. In addition to topography, AFM can also be used to measure various surface properties, including electrical, magnetic, and mechanical properties.

AFM has a wide range of uses in materials science, chemistry, physics, and biology. In materials science, AFM is used to study the properties of surfaces and interfaces, and to characterize materials on the nanoscale. In chemistry, AFM is used to study the structure and properties of molecules and molecular assemblies. In physics, AFM is used to study the properties of surfaces, interfaces, and thin films. In biology, AFM is used to study the structure and properties of biological molecules, such as proteins and DNA, and to image living cells and tissues. Overall, AFM is a powerful tool for investigating the properties and behavior of materials at the atomic and molecular scale.