When it comes to electronics, thin films of diamond hold a glittering promise. Diamond carries heat rapidly, is a magnificent insulator, and, when laced with the right impurities, is a better semiconductor than silicon. But until recently, researchers have not been able to fashion the thin layers of single diamond crystals on inexpensive surfaces required to make practical devices.
Scientists at North Carolina State University and Oak Ridge National Laboratory appear to have solved the problem. Building on work done last year in South Africa, they implanted carbon ions into copper, then used lasers to melt the copper. Since carbon can't dissolve in liquid copper, the carbon atoms rise to the surface and form a thin layer of diamond atop the molten metal. Some of the film was made of single crystals. The method is a big step forward, says Max Yoder, a program manager at the Office of Naval Research, and "it has far-reaching implications." That's because the technique might also be useful for making defect-free crystals in other key semiconductor materials, such as gallium arsenide or silicon carbide.