What is Amorphous Silicon?

In recent times a new field of materials science has opened up based on the special properties of amorphous materials. These are substances like glasses, ceramics and even metals which have no long-range order in their structure. These materials possess special properties which make them suitable for technological applications. They are often inexpensive to prepare and their properties can be engineered to suit particular applications.

Amorphous silicon is a glassy form of silicon, one of the most common elements in the Earth's crust. It is easy to prepare and has some special properties, which make it very suitable for use in electronic devices like position-sensitive detectors, field effect transistors and solar cells.

How is Amorphous Silicon prepared?

Amorphous silicon can be prepared in several different ways. The most common is to decompose silane gas (SiH₄) by using a radio frequency discharge in a vacuum chamber. The silicon produced in this process may be deposited in very thin films on substrates such as glass, stainless steel or ceramic. This makes amorphous silicon a promising material for large-scale use in thin film solar cells.

Why is more research required?

Amorphous silicon is a relatively new material. Although considerable work has been done on it over the past 20 years, there is still a vast amount more required. We need to find better ways of making it, faster ways of depositing it, and ways of fabricating it into electronic devices. One of its main shortcomings at present is that its properties tend to change under illumination or heating and this can reduce the effectiveness of any device that uses it. Ways need to be found to stabilise the material so that it achieves its full potential.

What does the future hold?

There are almost unlimited potential applications for amorphous thin film semiconductors like hydrogenated amorphous silicon. However, there are still many materials science problems that must be overcome before amorphous semiconductors achieve their full potential. One possibility is that amorphous silicon, because of its special attributes of low-cost and ease of preparation, could become the mainstay of the solar cell industry. In the future we could see huge arrays of solar cells collecting sunlight and converting it into electricity. This is not science fiction - the costs of doing this are falling rapidly and within a decade, large-scale electricity production from solar cells may be a reality. Amorphous silicon is one of the leading contenders for this role.