AVS 56th International Symposium & Exhibition
    Surface Science Monday Sessions
       Session SS1+EM-MoA

Paper SS1+EM-MoA11
Surface-driven Method for Incorporation of Mn into Ge Quantum Dots

Monday, November 9, 2009, 5:20 pm, Room M

Session: Semiconductor Surfaces and Interfaces I: Ge and III-V's
Presenter: C.A. Nolph, University of Virginia
Authors: C.A. Nolph, University of Virginia
K.R. Simov, University of Virginia
P. Reinke, University of Virginia
Correspondent: Click to Email
Magnetically doped nanostructures and quantum dots are important building blocks in future spintronic devices. We study the feasibility of magnetic doping of Ge quantum dots with Mn, an element with a large magnetic moment. A surface-driven route for Mn incorporation in Ge quantum dots promises superb control of the doping process. The Ge quantum dots are known to grow by strain-driven self-assembly (Stranski-Krastanov growth). Two pathways for Mn-doping have been identified: firstly, trapping of Mn at the Si-Ge interface and incorporation during quantum dot growth, and secondly, the deposition of Mn on the Ge quantum dot surface and dissolution of Mn during an annealing process. The first route requires a precise control of the Mn-bonding state at the Si(100) 2x1 substrate prior to the growth of quantum dots. Mn was deposited on Si(100) 2x1 and the surface phase diagram was determined across several temperature regimes and monitored with scanning tunneling microscopy. Mn-wire structures which formed at room temperature degrade and agglomerate to form Mn-clusters (115 - 270°C ± 30°C), then Mn moves into subsurface sites (316°C ± 38°C), and the onset of Mn-silicide formation is observed at about 342 - 416°C. This sequence is driven by the kinetics of the surface reaction between Mn and Si. A photoelectron spectroscopy study of the Si-Mn and the Si-Mn-Ge interface yields further insight into the bonding at the respective interfaces. The second route to dope quantum dots, namely the room-temperature deposition of Mn on Ge quantum dots, reveals the formation of Mn clusters, whose position is defined by the reconstruction of the Ge{105} facets. The diffusion of Mn on Ge(100) and Ge{105} facets, and into the Ge quantum dots is observed with STM during the annealing process. Our observations offer a comprehensive understanding of the Mn-interaction with all surfaces of relevance in the Si-Ge quantum dot system. The feasibility of the surface-driven route for Mn doping of Ge quantum dots will be discussed.