Now we are beginning to reach the end of this course. Before we leave, Sally will give you a brief summary of the basics of semiconductors and I will take a quick peek at the future.

Today, computers and computer chips are everywhere. The key to this technological revolution is the semiconductors. These are materials with the ability to conduct a current somewhere between good conductors (metals) and insulators. Semiconductors are very sensitive to impurities. By adding just small amounts of certain materials to them in a process known as "doping," we can greatly change their ability to conduct electricity.

By combining differently doped areas of a semiconductor, we may guide the flow of current through its different parts. It is also possible to control the current using external control voltages, like in a transistor. Today, engineers are able to construct incredibly advanced structures, such as microprocessors, on tiny pieces of semiconductor material. In the early days of the semiconductor industry, the material germanium was most common. Today however, silicon has proven to be much more effective.

In a world where computers become faster and faster each year, semiconductor components, like chips and transistors, must be made smaller and smaller. This means that we will eventually reach a limit on how much faster and more effective the Silicon based technique can be made (in fact, devices operating with just a single electron have already been demonstrated). "What happens then?" you might ask yourself. Well we don't know for sure, but today's scientists are working hard to find new materials or to improve old ones. In the future, large molecules might do the work that transistors do today. This field is called Molecular Electronics. So hopefully (if you like information technology, that is) computers can continue to evolve for a long time to come.