Two Stage Growth of Dispersed Nanoparticle Layers Suitable for Giant Magnetoresistance Sensors

摘要

During this award, accomplishments were made in two areas: deposition of anisotropic ferromagnetic nanoparticles and etching of metallic materials. (a) The grantees developed a technique to deposit partially anisotropic Fe nanoparticles, 200 A x 70 A x 8 A on Ag(1 11) with a uniform directionality. The investigators also found that in UHV, the silver atoms spontaneously diffuse on top of the Fe nanoparticles even a 300 K. Since silver is much more difficult to etch than iron due to the lack of volatile silver halides, this spontaneous coating of Fe by Ag explains the difficulty etching Fe particles deposited on Ag substrates. (b) The grantees also investigated the basic mechanisms of etching of Al(111) by a halogen gas, ICl. Halogen etching of metallic materials is a critical step in fabrication of magnetic sensors, spin valves, and giant magnetoresistive sensors. They found that for ICl/Al(111) the primary chemisorption process is remote dissociation in which the substrate harpoons in incoming ICl molecule with an electron. The dominant chemisorption process is abstraction in which ICl deposits the iodine atom onto the surface while the chlorine is ejected back into the gas phase.