Metals deposited on oxides tend to form bumpy clusters rather than nice, flat layers. But Scott Chambers of Sandia National Laboratories and his colleagues coaxed cobalt metal into accumulating layer by layer on a sapphire substrate (sapphire is a form of aluminum oxide) by enlisting the help of hydroxyl molecules, which produced a surface chemical reaction that led to the desired laminar growth. "For industry, a solution may be as simple as exposing the thin aluminum oxide films to a low pressure of water vapor before adding a final cobalt layer," Chambers offers. The team notes that the process--which can be carried out at room temperature--should be applicable not just to cobalt and sapphire but to a wide range of metals and metal oxides.
"Many advanced technologies rely on strong interfaces between metals and oxides," Chambers says. "These findings may provide the molecular insight industry needs to create better materials for microelectronics and sensors." The new work could have an especially significant impact on efforts to develop a new kind of computer memory known as magnetic random access memory, or MRAM, in which data is stored in metal-and-oxide sandwiches that retain their magnetic states regardless of whether the power is on or off. (Hence, the promise of computers that will boot up instantly.) MRAM devices are expected to go on the market in the next few years.
