This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Application of Nanowires”.
1. Why are nanowires proposed to be used in MOSFETs?
a) Poor gate control over channels
b) High aspect ratio
c) Involves bulky recombination
d) No channel electrostatic potential
View Answer
Explanation: The high aspect ratio of nanowires controls the channel electrostatic potential when the gate dielectric remains wrapped around the nanowire channel. This would turn the transistor on and off effectively. Therefore, metal-oxide semiconductor field effect transistors make use of nanowires.
2. Which of these statements best describes nanowire lasers?
a) II-IV semiconductor heterostructures
b) Solid state laser using synthetic ruby crystal as its laser medium
c) Structures possessing low refractive index that allow low optical loss
d) Fabry-Perot resonator cavities with high reflectivity end facets
View Answer
Explanation: Nanowire lasers are lasers described as nanoscale, subwavelength lasers built from III-V semiconductor heterostructures. They have high refractive index which allow for low optical loss in the nanowire core. They are also referred to as Fabry Perot resonator cavities having end facets of the wire with high reflectivity.
3. Which of these is not an issue faced by the industries in using nanowires in commercial products?
a) Isolation of nanowires
b) Handling of nanowires
c) Integration of nanowires into electric circuits
d) Potential for ultimate sensitivity
View Answer
Explanation: There are certain challenges faced by the industries for the commercial utilization of nanowires. These include isolation, handling and integration of nanowires in an electric circuit while the conventional and manual pick and place approach is used. This leads to reduced throughput.
4. What is the main drawback of silicon nanowires used in FET devices for sensing?
a) Control over surface receptor density
b) Exponential decay of electrostatic potential
c) Fragmentation of antibody capturing units
d) Screening of dissolved molecules by counter ions
View Answer
Explanation: In field effect transistor (FET) devices the charges on dissolved molecules and macromolecules are screened by dissolved counterions. This happens because in most cases molecules bound to the devices are separated from the sensor surface by about 2-12nm. Consequently, the electrostatic potential arising from the charges on the analyte molecule decay exponentially towards zero with distance.
5. Silicon nanowires can be employed for the detection of nitro-aromatic explosives.
a) True
b) False
View Answer
Explanation: Silicon nanowires are employed in a number of sensing devices that include the utra-sensitive, real-time sensing of biomarker proteins for cancer, detecting nitro-aromatic explosives such as 2, 4, 6 Tri-nitrotoluene (TNT) in sensitives superior to those of canines. These wires are used for detecting single virus particles as well as measuring intermolecular forces with great precision.
6. What can increase the sensitivity of the cardiac biomarkers in detecting acute myocardial infarction?
a) Consolidation of antibody capturing units
b) Change in surface potential
c) More intimate binding to target protein
d) Tuning conducting channel
View Answer
Explanation: In order to increase the sensitivity of cardiac biomarkers in detecting an acute myocardial infarction directly from serum improvements need to be made in FET devices. This involves fragmenting the antibody capturing units and controlling surface receptor density. This would allow more intimate binding to the nanowire of the target protein providing better sensitivity.
7. Choose the incorrect statement from the following.
a) NAND gate constructed from undoped silicon nanowires can control Schottky barrier
b) Nanowires when cross each other, the juncture behaves as a quantum dot
c) Nanowires cannot be used to dielectrophoretic manipulation
d) Surface of nanowires favour physico-chemical reactions
View Answer
Explanation: NAND gate constructed from undoped silicon nanowires have the capability to control Schottky barrier to achieve low-resistance contacts by placing a silicide layer in the metal-silicon interface. It has been observed that two nanowires acting as photon waveguides when cross each other they form a juncture that behaves as a quantum dot. Nanowires are uniquely suited to dielectrophoretic manipulation owing to their high aspect ratio. The wires have large surface to volume ratio, which facilitates physico-chemical reactions on the surface of nanowires.
8. Why are high efficiency photovoltaic devices being created from nanowires?
a) Less sensitive to impurities
b) Increased material consumption
c) Poor gate control over channel
d) Retarding optical properties
View Answer
Explanation: Solar cells made of nanowires are less sensitive to impurities due to bulk recombination, in comparison to their bulk counterparts. This leads to reduction on material consumption since silicon wafers having lower purity can be used to achieve acceptable efficiency.
Sanfoundry Global Education & Learning Series – Nanotechnology.
To practice all areas of Nanotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.
If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]
