Difference between SEM and TEM

Difference between SEM and TEM

SEM (Scanning electron microscopes)

1. Types of electrons : It is based on scattered electrons that are emitted from the surface of a specimen

2. Sample preparation : Sample can be of any thickness and is coated with a thin layer of a heavy metal such as gold or palladium and mounted on an aluminum slab

3. Resolution : The resolution is up to 20nm

4. Magnification : The magnifying power of SEM is up to 100,000X

5. Image formation : SEM provides a 3 dimensional image. Secondary or back scattered electrons are captured, detected and displayed on computer screen

6. Application : SEM is used to study the topography and atomic composition of specimens

TEM (Transmission electron microscopes)

1. Types of electrons : It is based on transmitted electrons

2. Sample preparation : Laborious sample preparation is required. The sample has to be cut into thin sections so as to allow electrons to pass through it and are supported on TEM grids

3. Resolution : TEM has much higher resolution than SEM. It can resolve objects as close as 1nm

4. Magnification : The magnifying power of TEM is up to 5,000,000X

5. Image formation : TEM provides a 2 dimensional image. Transmitted electrons hit a fluorescent screen giving rise to a shadow image. The image can be studied directly by the operator or photographed with a camera

6. Application : TEM is used to study the interior of cells, the structure of protein molecule, the organization of molecules in viruses and cytoskeletal filaments and the arrangement of protein molecules in cell membranes