Quantitative TEM and STEM study of Pt-Nanoparticles Coarsening and Ge(Mn)-based Ferromagnetic Semiconductors
type: Dataset
contact point: Organization
  fn: CCSD
keyword: ferromagnetic-semiconductors
keyword: nanocolonnes-gemn
keyword: theses
keyword: semiconducteurs-ferromagnetiques
keyword: stem
keyword: coarsening
keyword: physcondcm-genphysics-physicscondensed-matter-cond-matother-cond-matother
keyword: infoeu-reposemanticsdoctoralthesis
keyword: gemn-nanocolumns
keyword: hrtem
keyword: murissement
keyword: nanoparticules-pt
keyword: pt-nanoparticles
landing page: https://theses.hal.science/tel-00998250
description: In this work, different system have been studied using transmission electron microscopy (TEM) methods: Pt nanoparticles (NPs) on amorphous carbon, Ge quantum dots (QDs), Mn incorporation in Ge QDs and GeMn nanocolumns (NCs) embedded in Ge or GeSn matrix. The coarsening of Pt NPs on amorphous carbon film was studied by high resolution TEM (HRTEM) after annealing at temperatures between 200°C and 300°C for periods of up to 160 hours. A significant increase of the average particle size is observed with increasing annealing time for all investigated temperatures. An in-situ annealing experiment reveals two coarsening stages. The first coarsening stage is dominated by Smoluchowski ripening whereas the second coarsening stage is dominated by surface Ostwald ripening. The Arrhenius-type dependence of the derived surface mass-transport coefficients yields an activation energy Ed = 0.84 ± 0.08 eV/atom for the surface diffusion of Pt atoms on an amorphous carbon substrate. Advanced TEM methods have be used to obtain direct determination of composition profiles with atomic resolution and large field of view by correlation of high angle annular dark field (HAADF) and electron energy loss spectroscopy (EELS) signals. This method was used to obtain a direct and precise quantification of Ge concentration at the atomic level for the SiGe system. The Ge concentration profile along the growth direction was explained by Ge surface segregation during the growth with a two-state exchange model. The incorporation of Mn in Ge QDs have been performed by molecular beam epitaxy (MBE) growth of GeMn. At growth temperature of 380°C, SiMn precipitates are formed. Lowering the growth temperature at 220°C allows limiting the lateral segregation of Mn in Ge and incorporating Mn in Ge QDs. Absolute chemical composition by STEM-EELS evidenced that the total atomic density in Ge(Mn) NCs is almost two times higher than in the Ge matrix. Structural analysis by HRTEM shows that the crystalline NCs exhib…
identifier: NNT: 2013GRENY020
issued: 2026-05-05T09:57:09.451769
language: fr
modified: 2026-05-05T09:57:09.451773

test_moissonnage_selune
type: Agent

Quantitative TEM and STEM study of Pt-Nanoparticles Coarsening and Ge(Mn)-based Ferromagnetic Semiconductors
type: Distribution
access URL: https://theses.hal.science/tel-00998250
format: HTML
issued: 2026-05-05T09:57:09.453280
modified: 2026-05-05T09:57:09.435707