Why is it in news?

Based on the process of inelastic quantum tunnelling, the Electrical Engineering department of Indian Institute of Technology, Bombay, is researching to develop an “electronic nose. The “nose” can differentiate between molecules based on their vibrational energies.

Details

• The IIT Bombay researchers have showed that, using inelastic quantum mechanical tunneling, it is possible to construct an artificial “nose” that differentiates between different odorant molecules by sensing their vibrational energies. Quantum effects can get washed out at room temperature, but they propose a way that is sturdy even at room temperature.
• The nose they have proposed is actually a one-dimensional “resonant tunnelling diode” – a quantum device that conducts only when it is excited by special discrete values of electrical energy.
• Essentially this is a modification of a quantum wire – a linear array in which the electrons can move in one dimension only. The device takes a quantum wire a little further in a modification without which we do not see room-temperature operation. It adds a double barrier structure — with a [potential] well in the middle — in the transport direction as well.
• A double potential barrier (like two barricades) is created on the quantum wire, which confines the electrons further to be enclosed in a small region. It is known in quantum mechanics that this allows the confined electrons to possess discrete values of energy. This device selectively allows electrons with specific resonant incident energies to tunnel through the barriers.
• The resonant tunneling diode shows a peak in the current but does not shut down completely away from the peak. The way the odorant molecule information enters is through the creation of a vibrational mode that modulates the current, specifically by opening up an inelastic channel for tunnelling wherein the electron loses energy in the form of vibration, Normally such vibrational signatures are washed out at higher temperatures, but the paper shows that for the proposed device they would persist at room temperature.
• Making the device involves fabricating a one-dimensional semiconductor device with a double barrier, using standard semiconductor fabrication technology. 

Conclusion

The device can help in bomb detection, where currently dogs are used, thus endangering their lives. This device can also be used in radioactive areas or in any hazardous enviounment for a variety of applications. It can also be used in agriculture for faster sorting the fresh produce from the degraded, rotten ones. This device, once fully creaded, can open a floodgate of opportunities. It will also augment India’s scientific prowess.

Source

The Hindu