This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Preparation of Thin Films”.
1. A process of electroplating, in which metals ions from the solutions are deposited on the cathode as a thin film in the presence of an applied external field is known as____________
a) Electroless deposition
b) Cathodic deposition
c) Anodic oxidation
d) Thermal oxidation
Explanation: Cathodic deposition is a standard method of electroplating where two metals electrodes are dipped into an electrolyte solution and on application of an external field across the electrodes, metal ions from the solution are deposited on the cathode as a thin film.
2. For Cathodic deposition which of the following statements is appropriate?
a) The charge is not balanced in the process of Cathodic deposition
b) Esterification take place in the electrolyte solution
c) The charge is balanced in the process of Cathodic deposition
d) Oxidation and reduction take place in the electrolyte solution but not in the electrodes
Explanation: In Cathodic deposition, which is a method of electroplating with the application of external field, the charges are always balanced and in order to balance the charges in the process, the anodic metal gradually dissolves in the electrolyte.
3. What is the factor that differentiates between Electroless deposition and Cathodic deposition?
a) Nature of electrolyte
c) External field
Explanation: Electroless deposition is similar to that of Cathodic deposition except that it takes place in the absence of applied external field whereas the Cathodic deposition take place in the presence of applied external field. Both the process are commonly used for the deposition of nickel films.
4. What should be the nature of the material of the substrates on which the deposition take place in Cathodic deposition?
a) Non metallic
Explanation: In both Electroless deposition (absence of external electric field) and Cathodic deposition (presence of external electric field) the disadvantage is that their use is limited mainly to the deposition of metallic films on to that substrates that are electronically conducting i.e. metals.
5. Which of the following can be used for producing oxide films on their surfaces during anodic oxidation?
a) La, Ce, Pr, Nd
b) He, Ne, Ar, Kr
c) Nh, Fl, Mc, Lv
d) Al, Ta, Nb, Ti
Explanation: Anodic oxidation is an electrolyte method for producing oxide films on the surfaces of metals such as Al, Ta, Nb, Ti and Zr. These metals form the anode which is dipped in the electrolyte and oxide ions get deposited on their surfaces. He, Ne, Ar, Kr are inert gases they have full electronic configuration hence wont undergo anodic oxidation.
6. The equilibrium thickness in the anodic oxidation process depends on which of the following factor?
a) Nature of electrolyte
b) Amount of electrolyte
c) Magnitude of the applied field
d) Weight of the electrode
Explanation: During anodic oxidation, on increasing the field strength more oxide ions diffuse through the oxide layer to the metal surface and hence, the oxide layer grows thicker. An equilibrium thickness is reached after some time which depends on the magnitude of the applied field. Anodic layer may also be formed by exposure of the metal to a glow discharge.
7. Which of the following process take place in the presence of required temperature?
a) Anodic oxidation
b) Cathodic oxidation
c) Electroless deposition
d) Thermal deposition
Explanation: Thermal oxidation is a process where a substance get oxidized in the presence of temperature. For example many substances oxidize in air at high temperature and in some cases the product is a n inert film which inhibits further oxidation. Oxidation increases as the temperature increases.
8. Chemical vapour deposition is a method which is used to obtain which of the following substance?
b) Non conducting polymers
c) Conducting compounds
d) Crystalline semiconductor
Explanation: Chemical vapour deposition is a method that make use of some of the principles involved in vapour phases transport reactions. It is used to obtain very pure films of crystalline semiconductors including III-V compounds.
9. In the chemical vapour deposition the films formed are formed by decomposition of what kind of substances?
a) Liquid molecules
b) Conducting polymers
c) Gaseous molecules
d) Solid molecules
Explanation: Chemical vapour deposition the films are formed by deposition of gaseous molecules, the decomposition can be achieved by for example, pyrolysis (i.e. heating), photolysis (i.e. irradiation with IR or UV light) or chemical reaction.
10. For the reaction given below which of the following statements is correct?
2SiI2⇄SiI4 + Si
a) The reaction decreases to the left hand side with decreasing temperature
b) The reaction increases to the right hand side with decreasing temperature
c) The reaction decreases to the right hand with decreasing temperature
d) The reaction increases to the left hand side with decreasing temperature
Explanation: The above reaction is an example of chemical vapour deposition where equilibrium is obtained between the various species and the position of the equilibrium varies with the temperature. In the above reaction, the reaction increases to the right hand side with the decreasing temperature and hence silicon may deposit on a cold substrate.
11. In the process of vacuum evaporation, which of the following substrate can be used?
a) Ceramics, glass, silicon
c) Amorphous solids
d) F-block elements
Explanation: During vacuum evaporation, the gaseous material deposits on the substrate and its surroundings as film. Various substrate materials are used, depending on the subsequent application of the film that is to be deposited. The typical substrates used are ceramics (Al2O3), glass, alkali halides, silicon, germanium, etc.
12. Which of the following factor is taken care while selecting the container in the process of vacuum evaporation?
a) Chemically reactive
b) Withstand low temperature
c) Withstand high temperature
Explanation: A wide variety of source material for evaporation may be used including metals, alloys, semiconductors, insulators, and inorganic salts. These are placed in the container made of for example tungsten, tantalum or molybdenum, which can withstand very high temperature and chemically unreactive towards the material being evaporated.
13. 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
Explanation: 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.
Sanfoundry Global Education & Learning Series – Solid State Chemistry.
To practice all areas of Solid State Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.