NANOELECTRONICS



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INTRODUCTION:
What is nano electronics?
Nanoelectronics is the technology of electronic devices on a nano scale level, generally defined as between 1 and 100 nanometers in size. (A nanometer is one-billionth of a meter; a sheet of paper is about 100,000 nanometers thick.). At a nanoscale level, materials can exhibit unusual physical, chemical and biological properties that can be harnessed to develop electronic devices with new or expanded capabilities.


The aim of Nanoelectronics is to process, transmit and store information by taking advantage of properties of matter that are distinctly different from macroscopic properties. The relevant length scale depends on the phenomena investigated: it is a few nm for molecules that act like transistors or memory devices , can be 999 nm for quantum dot where the spin of the electron is being used to process information.
In 1965 Gordon Moore observed that silicon transistors were undergoing a continual process of scaling downward, an observation which was later codified as Moore's law. Since his observation transistor minimum feature sizes have decreased from 10 micrometers to the 28-22 nm range in 2011. The field of nanoelectronics aims to enable the continued realization of this law by using new methods and materials to build electronic devices with feature sizes on the nanoscale.


NANO ELECTRONIC DEVICES:
Solid State Quantum Effect NanoElectronic Devices Solid-state quantum-effect nanoelectronic devices are the nearer-term alternative for continuing to increase the density and speed of information processing.
Quantum-effect switching devices tend to function better when they are made smaller. Solid state quantum-effect nanoelectronic devices might be made as small as approximately 12 to 25 nanometers across and still function effectively if they could be fabricated reliably and uniformly on that scale. These devices function by taking advantage of effects that occur on the nanometer scale due to quantum mechanics. The most desirable properties of solid-state quantum-effect devices are low power consumption and high speed. The essential structural feature that all of these devices have in common is a small “island” composed of semiconductor or metal in which electrons may be confined. This island of a nanoelectronic device assumes a role analogous to that of channel in FET. The extent of confinement of electrons in the island defines three basic categories of solid state nano-electronic devices:
1. Quantum dots: (or artificial atoms).Island confines electrons with “zero” classical degrees of freedom remaining.
2. Resonant tunneling devices: Island confines electrons with “one” or “two” classical degrees of freedom.

3. Single electron transistors: Island confines electrons with “three” classical degrees of freedom.

Quantum Dots:
A quantum dot is a portion of matter (e.g., semiconductor) whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. Stated simply, quantum dots are semiconductors whose electronic characteristics are closely related to the size and shape of the individual crystal. Quantum dots of different sizes can be assembled into a gradient multi-layer nanofilm.