Metastable Phase Formation in Thin Films and Multilayers

Abstract

It is well known that thin-film technology relies increasingly on multilayered structures. As dimensions become smaller, the interfacial or contact region assumes a larger and often dominant role in the performance or properties. Many examples come readily to mind. In magnetic hard disks, the active cobaltalloy layer, itself only about 50 nm thick, is grown either on a crystalline chromium thin film or directly onto amorphous nickel-phosphorous, and capped with a protective carbon or chromium-carbon coating (see Figure 1). The recording head “flies” at 90 mph and about 0.1 ü above this combination, which is expected to be mechanically durable and magnetically reliable for thousands of recordings. Atomic-scale multilayers are being investigated to provide the ability to “tune” the magnetic properties of the active recording layer or head materials. Exchange coupled magneto-optical media consisting of a few tens of angstroms of cobalt or nickel layers on amorphous TbFeCo alloys are showing promise for improving magneto-optical coupling while maintaining perpendicular anisotropy. In microelectronic circuits, aluminum or silicide contacts to silicon are essential to any device, and multilevel integration involving a series of metal, alloy, silicon (amorphous, poly- or monocrystalline) and dielectric layers (some of which might be 1-10 nm thick) are increasingly required to achieve large-scale integration. Metal-metalloid (e.g., MoSi, W-C) multilayers are used for x-ray optical elements. Artificially produced metallic superlattices and multilayers are being used to probe the fundamental magnetic, electronic, mechanical, and structural properties of metal-metal interfaces.