This set of Multiple Choice Questions & Answers (MCQs) focuses on “Nanomaterials – Set 6”.
1. What is the mechanism sequence for the synthesis for atomic layer deposition?
a) Generation-diffusion-absorption
b) Generation-precursor reaction-diffusion-absorption
c) Activation-diffusion-absorption
d) Precursor reaction-diffusion-absorption
View Answer
Explanation: In atomic layer deposition, first, growth surface is activated by using some precursors. After the activation of the surface, diffusion of another precursor is started which is absorbed by the activated surface by chemisorption- a monolayer growth approach. In physical vapour method generation is required and precursor reaction is characteristics of chemical vapour method.
2. Which method is best suited for monolayer deposition of materials?
a) Physical vapour deposition
b) Chemical vapour deposition
c) Atomic layer deposition
d) Lithography
View Answer
Explanation: Physical vapour deposition uses physio-sorption technique for the absorption of growth species, physio-sorption gives multilayer absorption as it binds molecules by weak forces. Lithography is not so sophisticated for obtaining monolayer. Atomic layer deposition is advanced chemical layer deposition with controlled one by one inlet of precursors which allows it to form monolayer.
3. Which method uses half reactions for the deposition of growth species?
a) Physical vapour deposition
b) Chemical vapour deposition
c) Atomic layer deposition.
d) Lithography.
View Answer
Explanation: Atomic layer deposition uses sequential use of reactants, first, one reactant activates the surface of the substrate for second reactant in first half cycle, second, second reactant get deposited on activated surface in second half cycle, and the cycle is complete. This cycle goes on. In other techniques there is no such inlet control for reactants.
4. For high purity of deposition in atomic layer deposition, which one is not correct?
a) Aggressive and complete reactions
b) No competing pathways reactions
c) Removal of unreactive reactants
d) Self decomposition
View Answer
Explanation: In atomic layer deposition, time for each half cycle is short, so fast kinetics reactions with non-equilibrium nature are required in both half cycle. Competing reactions will slow the formation or activation of surface and layers which will results in poor purity. Unreacted reactants should also be removed after each half cycle otherwise they will react in middle of cycles and purity will get effected. Self -decomposition will results in defects and impurity in crystal structure.
5. The state of precursor, best suited for atomic layer deposition is ______
a) Liquid
b) Solid
c) Gas
d) Plasma
View Answer
Explanation: For atomic layer deposition, precursor should in a state of volatile matter, which are liquid and gas, so liquid and gaseous state of precursor is preferred for deposition but plasma state of precursors give best results as they activates the surface very efficiently than other gaseous species due to their high energy.
Sanfoundry Global Education & Learning Series – Nanomaterials.
To practice all areas of Nanomaterials, here is complete set of Multiple Choice Questions and Answers.
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