As device sizes get smaller, the electrical properties of aluminum will not meet the new requirements," says Monteiro, a materials scientist in the Plasma Applications Group of Berkeley Lab's Accelerator and Fusion Research Division. "We need lower resistivity and greater resistance to electromigration." Electromigration is the drift of metal atoms when the conductor carries high current densities, which can create voids. He adds, "We also need something that's compatible with lower dielectric-constant materials," which have been introduced by chip manufacturers to improve insulation and reduce circuit delays.