DURIP 99 - Instrumentation for Deposition and Etching of Ferromagnetic Nanoparticles
Abstract
During this award, accomplishments were made in three areas: deposition of an isotropic ferromagnetic nanoparticles, etching of metallic materials, and oxidation of metals. (a) The grantees developed a technique to deposit partially anisotropic Fe nanoparticles, 200A x 76A x 8A on Ag(111) with a uniform directionality. The investigators also found that in UHV, the silver atoms spontaneously diffuse on top of the Fe nanoparticles even at 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 in 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(l II) the primarily 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. (c) The grantees investigated the oxidation of Al(111) by O2 and NO. Al(111) ii) was chosen since adsorbates do not diffuse on this surface at 300 K so the chemical dynamics can be investigated with room temperature STM. In both cases, it was found that chemisorption occurs via nonadiabatic charge transfer from the surface and results in abstractive chemisorption: one of the atoms from diatomic molecule sticks to the surface while the remaining atom is ejected back into the gas phase. In the case of NO, the reaction is chemically selective the oxygen sticks to the surface while the nitrogen is ejected back into the gas phase.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 19, 2000
- Accession Number
- ADA385762
Entities
People
- Andrew C Kummel
Organizations
- University of California, San Diego