Step 5: Specimen Coating: The specimen needs to be coated with the conductive material to view with scanning electron microscope. In the sputter, a discharge is formed between anode and cathode using a suitable gas (argon). The bombardment of gas ions on cathode material (usually gold) erode the target material and deposit it on the specimen (Figure 34.2). The target used in the sputter consists of 60% gold and 40% palladium. The uniform deposition of sputtered material (gold) form even coating on the surface of specimen and make the specimen conductive to perform scanning electron microscope.  

Figure 34.2 Mechanism of Sputter to coat specimen.

Observation: A typical Scanning electron microscopic image of E.coli Bacterium is given in the Figure 34.3.