Question

Why should a specimen contain no water if it is to be imaged by scanning electron microscopy?

A) Water causes the specimen to swell.
B) Water distorts the image.
C) The specimen will be observed in a vacuum, which will cause the water to freeze.
D) The specimen will be observed in a vacuum, which will cause the water to evaporate rapidly and damage the specimen.
E) Water attracts electrons.

Answer 1

A specimen must be dehydrated for SEM imaging because water would evaporate in the vacuum, damaging the specimen and interfering with imaging.

Step-by-step explanation:

A specimen should contain no water if it is to be imaged by scanning electron microscopy (SEM) because the specimen will be observed in a vacuum, which will cause the water to rapidly evaporate. This rapid evaporation of water can cause damage to the specimen as the water reacts with the low pressure of the vacuum environment.

Moreover, water can interfere with the imaging process by causing charging or beam-related artifacts due to interactions with the electron beam. To prevent such issues, the specimen undergoes a dehydration process and is often sputter-coated with metal to enhance image quality and minimize damage.