A recipe for amazing devices
Nanotechnology is a hot topic in science at the moment, but what is it that’s so special about making things very small? Nanoscale materials have a number of properties that make them behave in a fundamentally different way from the same material on a large scale.
Firstly, when a given quantity of material is broken up into pieces that are only a few nanometres across vastly more of the atoms lie on the surface than they would in a single lump with the same mass. This increases the surface area for reactions but it also changes the way the surface atoms are bonded. A combination of these effects makes many materials that would be inert in bulk behave in a very reactive manner when engineered into nanoparticles.
When semiconductor devices are created on the nano scale, these surface effects generate additional benefits. One of the performance limitations of devices like transistors and lasers is the presence of imperfections within the crystal lattice. These are simply a product of thermodynamics and are very difficult to totally eliminate in large-scale materials. However, when a structure is only a few atoms across the thermodynamics and internal stresses become quite different. It often takes more energy to create defects than to have a perfect lattice, leading to far better crystal growth. The small scale also means that you can stack materials that have different atomic spacing on top of each other in layers without the major disruptions to the lattice that would occur in large-scale devices, which is important in creating devices.
The second major change that happens as devices approach the nano scale is that quantum mechanics begins to play an increasingly important role in their behaviour.