Nanoscale evidence of erbium clustering in Er-doped silicon-rich silica

International audiencePhotoluminescence spectroscopy and atom probe tomography were used to explore the optical activity and microstructure of Er 3+-doped Si-rich SiO 2 thin films fabricated by radio-frequency magnetron sputtering. The effect of post-fabrication annealing treatment on the properties of the films was investigated. The evolution of the nanoscale structure upon an annealing treatment was found to control the interrelation between the radiative recombination of the carriers via Si clusters and via 4f shell transitions in Er 3+ ions. The most efficient 1.53-μm Er 3+ photoluminescence was observed from the films submitted to low-temperature treatment ranging from 600°C to 900°C. An annealing treatment at 1,100°C, used often to form Si nanocrystallites, favors an intense emission in visible spectral range with the maximum peak at about 740 nm. Along with this, a drastic decrease of 1.53-μm Er 3+ photoluminescence emission was detected. The atom probe results demonstrated that the clustering of Er 3+ ions upon such high-temperature annealing treatment was the main reason. The diffusion parameters of Si and Er 3+ ions as well as a chemical composition of different clusters were also obtained. The films annealed at 1,100°C contain pure spherical Si nanocrystallites, ErSi 3 O 6 clusters, and free Er 3+ ions embedded in SiO 2 host. The mean size and the density of Si nanocrystallites were found to be 1.3 ± 0.3 nm and (3.1 ± 0.2) × 10 18 Si nanocrystallites·cm −3 , respectively. The density of ErSi 3 O 6 clusters was estimated to be (2.0 ± 0.2) × 10 18 clusters·cm −3 , keeping about 30% of the total Er 3+ amount. These Er-rich clusters had a mean radius of about 1.5 nm and demonstrated preferable formation in the vicinity of Si nanocrystallites

Influence of Co layer thickness on the structural and magnetic properties of multilayers

International audienceThe correlated effects of the insertion of a Pt spacer between ferromagnetic and antiferromagnetic layers and of the variation of the Co layers thickness on the structural and magnetic properties of [ (Pt/Co tCo) 3 /Pt tPt /IrMn ] n multilayers have been studied. Samples with n = 1 and 7, t Co = 0.4 and 0.6 nm, t Pt = 0 and 0.4 nm have been investigated by tomographic atom probe and superconducting quantum interference device magnetometry. For spacer free samples (t Pt = 0), the structural investigation shows that when t Co = 0.4 nm, Mn and Ir atoms diffuse deeply in the (Pt/Co) multilayers. In contrast for t Co = 0.6 nm, the Mn and Ir diffusion is much reduced. Because Pt acts as a barrier against the Mn and Ir diffusion, this difference is less pronounced in samples with Pt insertion. The hysteresis loops shapes, the exchange bias fields and the saturation magnetization values were correlated with the structural properties of these samples and discussed, taking into account the susceptibility, exchange stiffness, and perpendicular magnetic anisotropy

Atomic scale investigation of silicon nanowires and nanoclusters

In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT) provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers

(Invited) Characterization and Metrology of Nanoclusters-Based Nanostructures by Atom Probe Tomography

International audienceSilicon nanoclusters (Si-nc) embedded in SiO2 matrix have recently attracted much interest as potential candidate for many applications compatible with CMOS processing: photovoltaic cells, memory devices, waveguide amplifiers... Light emission and carrier storage properties exhibited by Si-nc are directly linked to the clusters characteristics (size, distribution, composition, interface nature with surrounding matrix...). Therefore, an accurate control of these parameters is essential in order to improve these systems. Conventional spectroscopy and microscopy techniques often encounter some limits to give quantitative information about Si-nc, especially when clusters are not crystalline. Atom probe tomography (APT) provides a 3D chemical mapping of the analyzed material at atomic scale (crystalline or not). Since the implementation of laser to APT, it becomes possible to analyze semi-conductors and oxides. In the case of Si-nc embedded in silica, APT is able to provide an accurate measurement of precipitate diameter, distribution and interface composition. Accessing this level of accuracy will help to understand and control the Si-nc characteristics which govern the properties of these new materials. The principle of the Atom probe Tomography technique will also be presented as well as its contribution in this field

Depth resolution function of the laser assisted tomographic atom probe in the investigation of semiconductors

International audienceThe investigation of boron delta layers by tomographic atom probe (3DAP) is used to demonstrate that a depth profiling resolution of 0.9 nm (full width at half maximum) can be achieved. Results are compared with measurements provided by secondary ion mass spectrometry. The steepness is found to be below 1 nm/decade. In addition, silicon atomic planes are resolved in the real space demonstrating an in-depth spatial resolution of the 3DAP below 0.2 nm. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3186617

Depth resolution function of the laser assisted tomographic atom probe in the investigation of semiconductors

International audienceThe investigation of boron delta layers by tomographic atom probe (3DAP) is used to demonstrate that a depth profiling resolution of 0.9 nm (full width at half maximum) can be achieved. Results are compared with measurements provided by secondary ion mass spectrometry. The steepness is found to be below 1 nm/decade. In addition, silicon atomic planes are resolved in the real space demonstrating an in-depth spatial resolution of the 3DAP below 0.2 nm. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3186617

Investigation of the Si-rich silicon oxide by 3D atom probe tomography

International audienceSilicon rich silicon oxide multilayers for optical devices have been investigated by laser assisted wide angle atom probe tomography. Three dimensional mapping of silicon nanoclusters multilayers was obtained. The composition of the different phases were deduced and compared to theoretical concentration. These results evidenced a size distribution of the Si clusters diameter and an incomplete phase separation between silica and silicon particles

An Innovative Process Using Only Water and Sodium Chloride for Recovering Rare Earth Elements from Nd\textendashFe\textendashB Permanent Magnets Found in the Waste of Electrical and Electronic Equipment

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Recycling and valorization of Nd-Fe-B permanent magnets in WEEE

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Recycling and valorization of Nd-Fe-B permanent magnets in WEEE

International audienc