The Flat Face of Technology

Discover, September 1, 1993

Welcome to the technology of flatland. Researchers around the world are discovering ways to create thin films of chemicals, some only a few atoms thick, that can do many things no other substances can. Some are semiconductors that can be made into computer chips. Others have special magnetic properties that let them act as memory storage systems. Others are superconductors–they carry electric current without any resistance. And some thin films can make a knife edge as hard as a diamond.

To make a thin film, engineers fire a high-temperature beam of molecules (900 degrees Fahrenheit) into a vacuum chamber. The beam hits the surface of a wafer made out of silicon, silicon compounds, lanthanum aluminate, or another similar material. If the conditions are right, the molecules from the beam organize themselves into a crystal.

Getting the conditions right is no small task. First, the wafer’s surface has to be made of a perfect crystal similar to the one the molecules will form on top of it. (Since the structure of the crystal on the wafer pulls the falling molecules into its own order, a hexagonal crystal on the surface could not produce a thin film with a square crystal.) Next, the molecules have to spread evenly over the surface in a thin, perfect layer. And finally, the newly formed thin film has to cool down without last-minute crumpling.

Perfect thin films are as smooth and featureless as well-made mirrors. Imperfect films (like all the films in these photographs, taken at a magnification of 100 to 1,500 at the National High Magnetic Field Laboratory) are of no practical use, but they give engineers crucial hints for future efforts, such as which materials are the most likely to produce successful results and which techniques for depositing the chemicals on the surface work best. And flawed films give all of us a beautiful look at a strange two-dimensional world.