Study of the insertion of dopants in group IV based semiconductor nano-objects : from hyperdoping to lamellar alloys

Ce travail de thèse concerne l'étude des propriétés structurales et optiques de multicouches de SiO/SiO₂ dopées au phosphore et de couches minces de SiP et de GeP préparées par évaporation sous ultravide. Après recuit, la formation de nc-Si est observée dans les multicouches SiO/SiO₂ dopées avec du phosphore. Le phosphore est localisé principalement dans les nc-Si avec des concentrations pouvant atteindre 10 at.%, bien supérieures à la limite de solubilité du phosphore dans le Si massif. Une résonance de plasmons de surface localisés est mise en évidence dans le moyen infrarouge. Sa position peut être ajustée en variant la concentration de phosphore. Des simulations basées sur la théorie de Mie ont permis de déterminer le taux d'activation qui est voisin de 5% et la mobilité des porteurs qui est de l'ordre de 23,5 cm²V⁻¹s⁻¹. Afin d'empêcher la désorption et la diffusion du phosphore dans le substrat de silicium, la couche mince de Si:P est déposée entre deux couches de SiO₂ d'épaisseur 20 nm. La formation du composé SiP est observée après recuit à des températures supérieures à 950°C. Celui-ci cristallise dans une structure orthorhombique de groupe d'espace Cmc2₁. Les couches minces sont constituées de grains de SiP de taille voisines du micron qui coexistent avec des grains de silicium contenant 1 à 2% de phosphore. La structure lamellaire du SiP a été mise en évidence. Les premiers essais d'exfoliation en phase liquide ont été réalisés après décapage de la couche superficielle de SiO₂ et du silicium dopé. Il est montré qu'il est possible de détacher des morceaux de SiP du substrat de Si. Le composé GeP, qui est obtenu après recuit à 500°C, cristallise dans une structure monoclinique de groupe d'espace C2/m. Les couches minces sont constituées principalement de grains de GeP qui coexistent avec de plus petits grains de Ge présents au voisinage de la surface. Comme pour le SiP, le GeP est bien lamellaire et l'exfoliation en phase liquide conduit à détacher des morceaux de GeP du substrat.This thesis concerns the study of the structural and optical properties in P-doped SiO/ SiO₂ multilayers and thin layers of SiP and GeP. They are prepared by evaporation under ultrahigh vacuum. After annealing, Si nanocrystals formation is observed in P-doped SiO/ SiO₂ multilayers. P atoms are mainly located in Si nanocrystals’ core with concentrations reaching up to 10 at.%, i.e. well beyond the solid solubility limit of P in bulk Si. Infrared absorption measurements give evidence of a localized surface plasmon resonance. The variation of phosphorus concentration allows to tune its position. Simulations, based on the Mie theory, permit to determine both the free charge carrier density, from which a dopant activation rate of about 5% is obtained, as well as the mobility of about 23,5 cm²V⁻¹s⁻¹.To prevent the phosphorus desorption and diffusion in the Si substrate, the Si:P thin film is grown between two 20nm thick SiO₂ layers. The SiP compound formation is observed after an annealing process higher than 950°C. SiP crystallizes in an orthorhombic structure in the Cmc2₁ space group. The thin films are composed of SiP grains with a size close to the micrometer scale which coexist with Si grains containing 1 to 2% of phosphorus. The lamellar structure of SiP was identified. The first liquid phase exfoliation test was performed after an etching to remove SiO₂ surface layer and the doped silicon. It is shown that it is possible to detach SiP flakes from the Si substrate. The GeP compound, which is obtained after a 500°C annealing, crystallizes in a monoclinic structure in the C2/m space group. The thin films are mainly composed of GeP grains which coexist with small Ge grains close to the surface. As SiP, GeP is lamellar and the liquid phase exfoliation leads to GeP flakes tear off from the Si substrate

Étude de l’insertion de dopants dans des nano-objets semi-conducteurs du groupe IV : de l’hyperdopage aux alliages lamellaires

This thesis concerns the study of the structural and optical properties in P-doped SiO/ SiO₂ multilayers and thin layers of SiP and GeP. They are prepared by evaporation under ultrahigh vacuum. After annealing, Si nanocrystals formation is observed in P-doped SiO/ SiO₂ multilayers. P atoms are mainly located in Si nanocrystals’ core with concentrations reaching up to 10 at.%, i.e. well beyond the solid solubility limit of P in bulk Si. Infrared absorption measurements give evidence of a localized surface plasmon resonance. The variation of phosphorus concentration allows to tune its position. Simulations, based on the Mie theory, permit to determine both the free charge carrier density, from which a dopant activation rate of about 5% is obtained, as well as the mobility of about 23,5 cm²V⁻¹s⁻¹.To prevent the phosphorus desorption and diffusion in the Si substrate, the Si:P thin film is grown between two 20nm thick SiO₂ layers. The SiP compound formation is observed after an annealing process higher than 950°C. SiP crystallizes in an orthorhombic structure in the Cmc2₁ space group. The thin films are composed of SiP grains with a size close to the micrometer scale which coexist with Si grains containing 1 to 2% of phosphorus. The lamellar structure of SiP was identified. The first liquid phase exfoliation test was performed after an etching to remove SiO₂ surface layer and the doped silicon. It is shown that it is possible to detach SiP flakes from the Si substrate. The GeP compound, which is obtained after a 500°C annealing, crystallizes in a monoclinic structure in the C2/m space group. The thin films are mainly composed of GeP grains which coexist with small Ge grains close to the surface. As SiP, GeP is lamellar and the liquid phase exfoliation leads to GeP flakes tear off from the Si substrate.Ce travail de thèse concerne l'étude des propriétés structurales et optiques de multicouches de SiO/SiO₂ dopées au phosphore et de couches minces de SiP et de GeP préparées par évaporation sous ultravide. Après recuit, la formation de nc-Si est observée dans les multicouches SiO/SiO₂ dopées avec du phosphore. Le phosphore est localisé principalement dans les nc-Si avec des concentrations pouvant atteindre 10 at.%, bien supérieures à la limite de solubilité du phosphore dans le Si massif. Une résonance de plasmons de surface localisés est mise en évidence dans le moyen infrarouge. Sa position peut être ajustée en variant la concentration de phosphore. Des simulations basées sur la théorie de Mie ont permis de déterminer le taux d'activation qui est voisin de 5% et la mobilité des porteurs qui est de l'ordre de 23,5 cm²V⁻¹s⁻¹. Afin d'empêcher la désorption et la diffusion du phosphore dans le substrat de silicium, la couche mince de Si:P est déposée entre deux couches de SiO₂ d'épaisseur 20 nm. La formation du composé SiP est observée après recuit à des températures supérieures à 950°C. Celui-ci cristallise dans une structure orthorhombique de groupe d'espace Cmc2₁. Les couches minces sont constituées de grains de SiP de taille voisines du micron qui coexistent avec des grains de silicium contenant 1 à 2% de phosphore. La structure lamellaire du SiP a été mise en évidence. Les premiers essais d'exfoliation en phase liquide ont été réalisés après décapage de la couche superficielle de SiO₂ et du silicium dopé. Il est montré qu'il est possible de détacher des morceaux de SiP du substrat de Si. Le composé GeP, qui est obtenu après recuit à 500°C, cristallise dans une structure monoclinique de groupe d'espace C2/m. Les couches minces sont constituées principalement de grains de GeP qui coexistent avec de plus petits grains de Ge présents au voisinage de la surface. Comme pour le SiP, le GeP est bien lamellaire et l'exfoliation en phase liquide conduit à détacher des morceaux de GeP du substrat

Heavily Doped Si Nanocrystals Formed in P-(SiO/SiO 2 ) Multilayers: A Promising Route for Si-Based Infrared Plasmonics

International audienceAs building blocks of multifunctional materials involving coupling at the nanoscale, highly doped semiconductor nanocrystals are of great interest for potential applications in nanophotonics. In this work, we investigate the plasmonic properties of highly doped Si nanocrystals embedded in a silica matrix. These materials are obtained by evaporation of heavily Phosphorus-doped SiO/SiO2 multilayers in a ultrahigh vacuum chamber followed by rapid thermal annealing. For P contents between 0.7 and 1.9 at%, structural investigations at the nanoscale give clear evidence that P atoms are mainly located in the core of Si nanocrystals with concentrations reaching up to 10 at%, i.e. well beyond the solid solubility limit of P in bulk Si. Alloying and formation of SiP nanoparticles is observed for P contents exceeding 4 at% in the multilayer. Infrared absorption measurements give evidence of a localized surface plasmon resonance located in the 3 to 6 µm range. A core-shell structure was used to model Si nanocrystals embedded in a silica matrix. Based on the Mie theory and the Drude model, both the mobility and the free charge carrier density were extracted from the simulation, with values reaching 27 cm 2 V-1 s-1 and 2.3×10 20 cm-3 , respectively. This results in a dopant activation rate of about 8 %

Heavily Doped Si Nanocrystals Formed in P-(SiO/SiO 2 ) Multilayers: A Promising Route for Si-Based Infrared Plasmonics

International audienceAs building blocks of multifunctional materials involving coupling at the nanoscale, highly doped semiconductor nanocrystals are of great interest for potential applications in nanophotonics. In this work, we investigate the plasmonic properties of highly doped Si nanocrystals embedded in a silica matrix. These materials are obtained by evaporation of heavily Phosphorus-doped SiO/SiO2 multilayers in a ultrahigh vacuum chamber followed by rapid thermal annealing. For P contents between 0.7 and 1.9 at%, structural investigations at the nanoscale give clear evidence that P atoms are mainly located in the core of Si nanocrystals with concentrations reaching up to 10 at%, i.e. well beyond the solid solubility limit of P in bulk Si. Alloying and formation of SiP nanoparticles is observed for P contents exceeding 4 at% in the multilayer. Infrared absorption measurements give evidence of a localized surface plasmon resonance located in the 3 to 6 µm range. A core-shell structure was used to model Si nanocrystals embedded in a silica matrix. Based on the Mie theory and the Drude model, both the mobility and the free charge carrier density were extracted from the simulation, with values reaching 27 cm 2 V-1 s-1 and 2.3×10 20 cm-3 , respectively. This results in a dopant activation rate of about 8 %

Heavily Doped Si Nanocrystals Formed in P-(SiO/SiO 2 ) Multilayers: A Promising Route for Si-Based Infrared Plasmonics

International audienceAs building blocks of multifunctional materials involving coupling at the nanoscale, highly doped semiconductor nanocrystals are of great interest for potential applications in nanophotonics. In this work, we investigate the plasmonic properties of highly doped Si nanocrystals embedded in a silica matrix. These materials are obtained by evaporation of heavily Phosphorus-doped SiO/SiO2 multilayers in a ultrahigh vacuum chamber followed by rapid thermal annealing. For P contents between 0.7 and 1.9 at%, structural investigations at the nanoscale give clear evidence that P atoms are mainly located in the core of Si nanocrystals with concentrations reaching up to 10 at%, i.e. well beyond the solid solubility limit of P in bulk Si. Alloying and formation of SiP nanoparticles is observed for P contents exceeding 4 at% in the multilayer. Infrared absorption measurements give evidence of a localized surface plasmon resonance located in the 3 to 6 µm range. A core-shell structure was used to model Si nanocrystals embedded in a silica matrix. Based on the Mie theory and the Drude model, both the mobility and the free charge carrier density were extracted from the simulation, with values reaching 27 cm 2 V-1 s-1 and 2.3×10 20 cm-3 , respectively. This results in a dopant activation rate of about 8 %