Atomic Force Microscopy – AFM

Atomic Force Microscopy (AFM)

Atomic Force Microscopy (AFM) is a non-optical surface topographic technique with high lateral (nm), vertical (Aº), and force (pN) resolution. It is used for better resolution visualization of nanostructures, such as thin films, nanoparticles, microelectronics, polymers, cellular components, etc. It is also used to make quantitative measurements at the nanoscale and subnanoscale, including surface roughness and step-heights. It is built on the principles of scanning probe microscopy. It is used in the different modes for the qualitative mapping of mechanical properties (friction, adhesion), physical properties (size, morphology, surface texture, roughness), electrical properties (capacitance, conductivity, resistance, surface potential), and magnetic properties of material surfaces.

In AFM, a cantilever with a nanoscale tip scans across the sample surface and uses the atomic forces to map the tip-sample interaction. The most commonly used modes of AFM are contact, non-contact, and dynamic (tapping) modes.

Common Uses

• Imaging the surface morphology of clay particles dispersed in a polymer matrix
• Compositional mapping of polymer blends and copolymers
• Characterize trenches, holes, and lines at nanometer technology node in integrated circuit technology
• Measurement of nanoscale viscoelastic properties of cells, biopolymers, and tissues using Force-Distance (FD) curve of AFM in different modes
• Mapping of microstructures of the biological tissues such as brain, lung,  blood vessel, cartilage, and tendon, etc. with good resolution
• Diagnose the effects of cytotoxic drugs on the human body
• Determination of the thickness and surface roughness of a graphene layer
• Determination of the microrheological properties of thin fluid films for the development of MEMS devices
• Detection and characterization of microorganisms in foods

Advantages

• Able to study the surface properties of both conductive and non-conductive samples
• Simple sample preparation and no need for staining, labeling, or fixation 
• High-resolution 3D images enable the measurement of the height of the nanoparticles quantitatively
• Works in multiple mediums such as ambient air, controlled environments, and liquid dispersions

Limitations

• Scan range limit: Area 150×150 µm2, vertically 10-20 µm in the z-direction
• The scanning speed of AFM is slow compared with other microscopic techniques
• Tip convolution may result in an error in the images
• Tip or sample can be damaged
• Images can have an effect of cross-talk between the x, y, z axes and hysteresis of the piezoelectric material

Industries

• Semiconductors
• Advanced Materials
• Chemistry
• Cell Biology
• Molecular Biology
• Medical Sciences
• Nanotechnology
• Thin films and coatings

Laboratories 

• EAG Laboratories Inc.
• Jordi Labs
• Lucideon group
• Materials Evaluation and Engineering, Inc.
• National Renewable Energy Laboratory (NREL)

More Details

• Working principle of AFM
• Uses of AFM
• Applications of AFM
• Limitations of AFM