Structures

Nanotechnology has yielded a number of unique structures that are not found anywhere in nature.  Most demonstrate an essential quality of quantum mechanics known as quantum confinement.  The idea behind confinement is all about keeping electrons trapped in a small area.  The sizes we're talking about here for confinement have to be less than 30 nm for effective confinement.  Quantum confinement comes in several flavors.  2-D confinement is only restricted in one dimension, and the result is a quantum well (or plane).  These are what most lasers are currently built from.  1-D confinement occurs in nanowires.  0-D confinement is found only in the quantum dot.

You're probably wondering why confinement is so important.  For one thing, it leads to new electronic properties that are not present in today's semiconductor devices.  Consider the quantum dot.  The typical quantum dot is anywhere between 3-60 nm in diameter.  That's still 30 to 600 times the size of a typical atom.  A quantum dot exhibits 0-D confinement, meaning that electrons are confined in all three dimensions.  The only things in nature that have 0-D confinement are atoms.  So a quantum dot can be loosely described as an 'artificial atom'.  This is vitally important because we can't readily experiment on regular atoms.  They're too small and too difficult to isolate in an experiment.  Quantum dots, on the other hand, are large enough to be manipulated by magnetic fields and can even be moved around with an STM or AFM.  We can deduce many important atomistic characteristics from a quantum dot that would otherwise be impossible to research in an atom.

Confinement also increases the efficiency of today's electronics.  The laser is based on a 2-D confinement layer that is usually created with some form of epitaxy like Molecular Beam Epitaxy or Chemical Vapor Deposition.  The bulk of modern lasers created with this method are highly functional, but ultimately inefficient in terms of energy consumption and heat dissipation.  Moving to 1-D confinement in wires or 0-D confinement in quantum dots allows for higher efficiencies and brighter lasers.  Quantum dot lasers are currently the best lasers available though their fabrication is still being worked out.

All of these solid nanostructures are very important to nanotechnology research.  There are several other structures that are also academically interesting.  Nanotubes and Buckyballs are a class of materials that are hollow.  They are all based on carbon forms that are wrapped to form a shell.  The carbon nanotube, for instance, has drawn much attention as one of the principal nanostructures that exhibit some great potential in nano-electro-mechanical-systems (NEMS). 

In the following sections we shall discuss the many structures currently under investigation by researchers around the world.  After we've finished discussing these structures, we will move on to their numerous applications in industry and consumer goods.