This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Electrochemical Etching – 18”.
1. In interference lithography (IL) technique, aluminium is used as anode.
a) True
b) False
View Answer
Explanation: In this system and similar to electrochemical etching of silicon, the anode (i.e. aluminium foil) and cathode (e.g. platinum wire) are immersed in the acid electrolyte.
2. In IL technique, nanopores are produced by application of current and voltage.
a) True
b) False
View Answer
Explanation: The growth of nanopores is produced by the application of current or voltage. Note that the geometric features of pores in NAA can be precisely controlled by the anodization parameters.
3. Pore sizes in NAA can range from ____
a) 10—100 nm
b) 20—250 nm
c) 20—400 nm
d) 100—550 nm
View Answer
Explanation: Typically, pore sizes in nanoporous anodic alumina (NAA) technique can range from 20 to 400 nm, with a pore density from 5 × 108 to 3 × 1010 pores per cm2.
4. The NAA technique can produce silicon nano wires with high crystalline quality.
a) True
b) False
View Answer
Explanation: This lithographic approach makes it possible to produce silicon wires with controlled geometry, morphology and size with high crystalline quality and smooth surface.
5. The geometric features of the resulting silicon nanowires are independent of the noble-metal thickness.
a) True
b) False
View Answer
Explanation: The geometric and morphological features of the resulting silicon nanowires are dependent on the thickness of the noble metal film.
6. The pores produced by RIE etching can have a thin defective region.
a) True
b) False
View Answer
Explanation: The pores produced by RIE etching can have a thin defective region, which can prevent or hinder the metal-assisted etching process. To overcome this drawback, the same authors used a slight modification of the traditional NAA approach in order to avoid the use of RIE etching.
7. In the aforementioned approach (modified approach), which of the following metals is used?
a) V
b) Cr
c) Pt
d) Ag
View Answer
Explanation: In this new approach, a film of Ag is deposited on the NAA mask and the whole system etched. In this way, the Ag film with holes was transferred from the top of the NAA mask to the surface of the silicon substrate as a result of the dissolution of the NAA mask. Then, the etching occurred on the surface of the silicon by metal-assisted etching catalysed by the Ag film.
8. The use of NAA mask technique to produce pSi structures need simple wet chemistry laboratory.
a) True
b) False
View Answer
Explanation: The main advantage of the use of NAA masks to produce pSi structures by metal-assisted etching is that it can be carried out in a simple wet chemistry laboratory without expensive facilities.
9. Self-ordered NAA structures do not present any defects and domains.
a) True
b) False
View Answer
Explanation: Self-ordered NAA structures present defects and domains, which are inevitably transferred to the patterned structure on the silicon substrate and thus to the resulting arrays of silicon nanowires.
10. The NAA approach can produce silicon nano-wires of _____ cross-section.
a) triangular
b) circular
c) square
d) needle like
View Answer
Explanation: Along with the production of self-ordered pores, another limitation of this approach is that only silicon nanowires featuring circular section can be obtained.
11. Nanosphere lithography method is another lithographic approach extensively used to produce pSi structures.
a) True
b) False
View Answer
Explanation: Nanosphere lithography method is another lithographic approach extensively used to produce pSi structures by metal-assisted etching. Huang et al. developed an approach where a monolayer of self-assembled polystyrene (PS) nanospheres was first deposited on the surface of a silicon substrate. After this, the size and distance between adjacent nanospheres were increased by RIE etching and a noble metal film was deposited on the silicon surface by thermal evaporation.
12. At high aspect ratio, silicon nanowires tend to form bundles.
a) True
b) False
View Answer
Explanation: It is worthwhile mentioning that silicon nanowires of high aspect ratio trend to form bundles or collapse as a result of surface tension forces during the drying process. This drawback can be overcome by supercritical drying approach.
13. Porous silicon can be used as carriers for drug delivery.
a) True
b) False
View Answer
Explanation: Its biocompatibility and degradability properties have enabled the use of porous silicon structures as micro and nanocarriers for drug delivery. While it’s outstanding optical properties make porous silicon a unique material to develop optical structures suitable for optical sensing.
Sanfoundry Global Education & Learning Series – Manufacturing Processes.
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