Question

Compare and contrast scanning tunneling microscopy (STM) and atomic force microscopy (AFM)? List at least two advantages and two disadvantages for both methods. Please reference at least one source in your discussion. (It may be a textbook.)

Answer 1

AFM stands for atomic force microscopy and STM stands for scanning tunneling microscopy.Comparison between the two is listed here:

1. AFM captures precise images by moving a nanometer sized tip across the surface of the image. The STM captures images using quantum tunneling.

2. In AFM the probe makes a direct contact with the surface or calculates the incipient chemical bonding . The STM images indirectly by calculating the quantum degree tunneling between the probe and sample.

3. The tip in AFM touches the surface gently touches the surface whereas in STM, the tip is kept at a short distance from the surface.

Advantages of AFM OVER STM

1 AFM resolution is better than the STM. This is why AFM is widely used in nano-technology.

2.Scanning Tunneling Microscope is normally applicable to conductors whereas Atomic Force Microscope is applicable to both conductors and insulators.

3.The AFM suits well with liquid and gas environments whereas STM operates only in high vacuum.

Disadvantages of AFM

1. A disadvantage of AFM compared with the scanning electron microscope (SEM) is the single scan image size. In one pass, the SEM can image an area on the order of square millimeters with a depth of field on the order of millimeters. Whereas the AFM can only image a maximum height on the order of 10-20 micrometers and a maximum scanning area of about 150×150 micrometers.

2. The scanning speed of an AFM is also a limitation.

Advantages of STM

1. STMs are versatile. They can be used in ultra high vacuum, air, water and other liquids and gasses.

2. They will operate in temperatures as low as zero Kelvin up to a few hundred degrees Celsius.

3.It is capable of capturing much more detail than lesser microscopes. This helps researchers better understand the subject of their research on a molecular level.

REFEENCE:https://www.springer.com/cda/content/document/cda_downloaddocument/9783642152825-c1.pdf?SGWID=0-0-45-1173242-p174031068