| AVS 57th International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures | Wednesday Sessions |
| Session MI-WeA |
| Session: | Spintronic Devices and Proximity Effects |
| Presenter: | K.R. Simov, University of Virginia |
| Authors: | K.R. Simov, University of Virginia C.A. Jenkins, Lawrence Berkeley National Laboratory M. Liberati, Lawrence Berkeley National Laboratory P. Reinke, University of Virginia |
| Correspondent: | Click to Email |
The magnetic doping of the group IV semiconductors Si and Ge with Mn is coveted as valuable component in novel spintronics devices. Their magnetic doping is hampered by the low solubility of Mn in both elements, and the formation of silicide and germanide phases which modify or suppress the magnetic response of the material. We therefore investigate Mn-nanostructures which are synthesized on the Si(100)(2x1) surface and then capped with a layer of Si or Ge to protect the integrity of the nanomaterial. The Mn-nanostructure is therefore embedded as a delta-doped layer within a group IV semiconductor matrix.
The first section of our presentation focuses on nanostructure synthesis, in particular the growth of monoatomic Mn-wires on the Si(100)(2x1) surface, where the dimer row structure guides the wire formation. A scanning tunneling microscopic (STM) study establishes the relation between the nanostructure type and the quality of the substrate, which is expressed in the concentration of defects prior to Mn deposition. An increasing defect concentration (1.0 % to 18.2%) leads to a suppression of wire formation and the growth of ultrasmall Mn-clusters is favored, which allows for an excellent control of nanostructure type. Surface structuring through the presence of dimer vacancy lines, or narrow terraces offer an additional route to control Mn-wire formation. A Monte-Carlo based model is introduced to describe the surface processes which lead to wire-formation.
The second section of our presentation assesses the stability of the nanostructures during the growth of the Si or Ge caps. The capping of nanostructures is indispensible for preservation of the nanostructures’ unique capabilities in devices, and is critical for magnetic measurements such as VSM (vibrating sample magnetometry) and XMCD (X-ray magnetic circular dichroism, Advanced Light Source, Lawrence Berkeley National Laboratory). An STM observation of the growth process of the Si and Ge caps shows that the Mn-nanostructures are indeed preserved, and we are therefore able to assess the magnetic properties of Mn-wires and ultrasmall clusters.
The third section of our presentation is devoted to the discussion of the magnetic properties of the Mn-wire and Mn-cluster structures. The role of magnetic anisotropy, the ionic and metallic contributions from the Mn-nanostructure, and the nature of the magnetic coupling within the respective nanostructure, and with the cap-material will be discussed.
The support from NSF-Chemistry and DOE are gratefully acknowledged.