Nanotechnology

[FreeGrass]

Nanoelectronic gemstone

DIAMONDS, gemstones have always amazed us with their colors. Now in the era of nanotechnology, it's the Quantum Dot (QD) that is dazzling our eyes. QDs are semiconductor nanostructures, 25 billionths of a meter in diameter, which can confine electrons in three dimensions and emit light when exposed to ultraviolet radiation or X-ray. About 50 thousandth the width of a human hair, these nano-scale gems are built by confining electrons in some insulating material(s) around a central, well-conducting region. Although they can be composed of hundreds of atoms, quantum dots in many ways behave almost as if they were single gigantic atoms. This enables the study of quantum mechanical effects on a length scale that is around 100-500 times larger than the pure atomic scale.

QDs display unique optical and electrical properties that are different from bulk material. Excited QDs emit light, this emission depends not only on the material from which the QD is made, but also on the dot's size. QDs can therefore be “tuned” during production to emit any color of light desired. The smaller the dot, the closer it is to the blue color, and the larger the dot, the closer to the red end of the spectrum. QDs can even be tuned beyond visible light.

These glittering nanostructures are now in action at different technological war-fronts. QD lasers can be operated at wavelengths previously not possible using semiconductor laser technology. QD light-emitting diodes can be incorporated into a new generation of applications such as flat-panel TV screens, digital cameras, mobile phones, personal gaming equipments.

QD technology is one of the most promising candidates for use in solid-state quantum computation. With several entangled QDs, quantum bits (qubit) are realizable. QDs as a source of pairs of entangled photons can play a major role in the development of quantum information technologies. QD detectors can be used in medical and environmental sensing, optical communications, thermal imaging, night vision cameras, and missile tracking and recognition. In modern biological analysis, organic dyes are being replaced by QDs. QDs have been tested in most biotechnological applications that use the fluorescence, including DNA recognition, cell animal biology, biological motion tracking.

Research on new generation of 31% to 42% efficient Photovoltaic devices using QDs may be the next big breakthrough in our energy crisis. With so many potentials, QD is a technology for everyone to keep an eye on.

The author is a freelance science enthusiast and student of electrical engineering in BUET.