1. Briefly answer the following questions. You may use diagrams if necessary. a. In modern thin film deposition systems, the substrates are placed on a rotating platen. What is the purpose of the rotation? b. Consider deposition of 2 different thin films, film A with an activation energy (EA) of 1.5eV and film B with an activation energy of 2 eV. Each growth is in separate reactors. We know that both the films can be grown at 400 " C. If both the reactors are set at 400 "C, which film will have a higher growth rate? State your reasoning. c. The critical radius of nucleus of material C is composed of 100 atoms and material D critical nucleus radius is reached with 1000 atoms. If both the materials are grown under identical conditions, which film will grow first? State your reason. d. Why is it difficult to dope amorphous Si (a-Si) but easier to dope hydrogenated amorphous Si (a-Si:H)? e. If you were given 3 wafers, all with a 1 um thick silicon film and told that one wafer had an amorphous film, another had polycrystalline film, and the third had an epitaxial film. How would you identify each film if you had all the necessary tools available