Question

State which of the following is correct regarding the process of vacuum evaporation?

(a) The surface of the substrate should be thoroughly cleaned

(b) The substrate should not be used at all

(c) Container used in the process should be chemically active with evaporation

(d) The source material used should be made up of glass or diamond

I have been asked this question in class test.

The query is from Preparation of Thin Films in chapter Preparative Methods of Solid State Chemistry

Answer 1

Correct option is (a) The surface of the substrate should be thoroughly cleaned

The best I can explain: It is important to clean the substrate surface prior to the evaporation by a sequence of steps involving, ultrasonic cleaning in for example, a detergent solution, decreasing in, for example, alcohol, degasing under vacuum and finally ion bombardment to remove the surface layers from the substrate.