Optical absorption spectra were used to study F centre evolution in LiF samples bombarded with 56... more Optical absorption spectra were used to study F centre evolution in LiF samples bombarded with 56 MeV α-particles and 28 MeV deuterons at room temperature. Results on the decay of the F-band show that it does not follow first order kinetics. While this band decreases, a Y-band increases in the M-region at 2.74 eV. The presence of a constant OD point I, located between these two bands, allowed the calculation of the Y-band half-width (ΔEY = 0.240 eV). Emission spectra show that the Y-band is in fact the F-band and it suggests to consider the F centre migration by the following process: F + F F.A l'aide des spectres d'absorption optique, nous étudions l'éevolution des centres F crées dans LiF par bombardement avec des particules alpha de 56 MeV et des deutons de 28 MeV, à la température ambiante. L'étude de la cinétique de décroissance de la bande F montre que le processus n'est pas du premier ordre, d'autre part, pendant cette cinétique nous voyons croître dans la région M une bande Y dont le maximum est situé à 2,74 eV. La présence d'un point I de densité optique constante situé entre cette bande Y et la bande F, permet de calculer la largeur à mi-hauteur de la bande Y (ΔEY = 0,240 eV). Les spectres d'émission permettent d'identifier la bande Y avec la bande F, ce qui nous conduit à envisager la migration du centre F dans le processus F + F F.
Colour centres are induced in LiF by bombardment with 56 MeV α-particles and 28 MeV deuterons at ... more Colour centres are induced in LiF by bombardment with 56 MeV α-particles and 28 MeV deuterons at room temperature. The nature and the evolution of these centres are studied by optical absorption spectra obtained at 300 and 77 °K, and after thermal annealing. F-centres and F-aggregate centres are observed as well as many ionized F-aggregate centres (F, F, F, F) and some other bands near 2750, 4250, 4400, 4950, and 5300 Å at LNT. The 4250 and 4400 Å bands exhibit a weak vibrational structure. When samples are annealed at temperatures above 600 °K, only the 2750 Å band and a wide flat band near 4350 Å remain; it is suggested that they are colloidal bands.Nous avons étudié les centres colorés créés dans LiF, par bombardement, à la température ambiante, avec des particules alpha de 56 MeV et deutons de 28 MeV. La nature et l'évolution des centres présents sont étudiées d'après le spectres d'absorptions optique, obtenus à 300, 77 °K et après des recuits successifs. Cette étude montre qu'en plus des centres F et agglomérats de F il apparait plusieurs centres chargés (F, F, F, F) ainsi que de nouvelles bandes dont les maxima se situent vers 2750, 4250, 4400, 4950 et 5300 Å à 77 °K. Les bandes à 4250 et 4400 Å présentent une faible structure vibrationnelle. Sur les échantillons recuits à des températures supérieures à 600 °K nous n'observons plus que la bande à 2750 Å et une bande très large dont le maximum se situe vers 4350 Å. Nous pensons que ces bandes sont dues à la présence de colloides.
ABSTRACT The low energy cluster beam deposition technique (LECBD) is developed to prepare origina... more ABSTRACT The low energy cluster beam deposition technique (LECBD) is developed to prepare original nanostructured systems from clusters preformed in the gas phase. The nucleation and growth mechanism specific of the cluster deposits is studied Ln view to control the nanostructured morphology of the cluster assembled films, especially for future applications to high areal density devices. Examples of the synthesis and properties of metallic nanostructures as well as covalent ones are presented. In the first case, systems from noble metal clusters (Ag, Au, and AgxAu1-x) and transition metal based clusters (CO, SmCo5) assemblies are studied for their original optical or magnetic properties, respectively. In the second case, covalent se mi conducting films exhibiting specific electronic structures are obtained by Si, C, and SixC1-x cage like clusters (fullerenes and heterofullerenes) depositions.
This paper presents recent results on the preparation and characterization of original magnetic n... more This paper presents recent results on the preparation and characterization of original magnetic nanostructures from nanoclusters preformed in the gas phase. Magnetic binary-clusters (i.e. Co-Sm, Co-Pt, Co-Ag) with rather well controlled sizes, structures and compositions, are prepared in the gas phase using a combined laser vaporization-rare gas condensation source and subsequently deposited at low energy (LECBD : Low Energy Cluster Beam Deposition) on various functionalized substrates to grow cluster-assembled magnetic nanostructures exhibiting specific magnetic properties. Especially a high magnetic anisotropy and consequently a high magnetic blocking temperature compatible with future applications to high density memory devices and spin electronics are expected. In this context of applications, 2D-organized arrays of functionalized binary-cluster assembled dots are prepared by LECBD on FIB-functionalized substrates (FIB: Focussed Ion Beam) with the ultimate objective to reach areal densities in the range of the Tbits/in2.
Optical absorption spectra were used to study F centre evolution in LiF samples bombarded with 56... more Optical absorption spectra were used to study F centre evolution in LiF samples bombarded with 56 MeV α-particles and 28 MeV deuterons at room temperature. Results on the decay of the F-band show that it does not follow first order kinetics. While this band decreases, a Y-band increases in the M-region at 2.74 eV. The presence of a constant OD point I, located between these two bands, allowed the calculation of the Y-band half-width (ΔEY = 0.240 eV). Emission spectra show that the Y-band is in fact the F-band and it suggests to consider the F centre migration by the following process: F + F F.A l'aide des spectres d'absorption optique, nous étudions l'éevolution des centres F crées dans LiF par bombardement avec des particules alpha de 56 MeV et des deutons de 28 MeV, à la température ambiante. L'étude de la cinétique de décroissance de la bande F montre que le processus n'est pas du premier ordre, d'autre part, pendant cette cinétique nous voyons croître dans la région M une bande Y dont le maximum est situé à 2,74 eV. La présence d'un point I de densité optique constante situé entre cette bande Y et la bande F, permet de calculer la largeur à mi-hauteur de la bande Y (ΔEY = 0,240 eV). Les spectres d'émission permettent d'identifier la bande Y avec la bande F, ce qui nous conduit à envisager la migration du centre F dans le processus F + F F.
Colour centres are induced in LiF by bombardment with 56 MeV α-particles and 28 MeV deuterons at ... more Colour centres are induced in LiF by bombardment with 56 MeV α-particles and 28 MeV deuterons at room temperature. The nature and the evolution of these centres are studied by optical absorption spectra obtained at 300 and 77 °K, and after thermal annealing. F-centres and F-aggregate centres are observed as well as many ionized F-aggregate centres (F, F, F, F) and some other bands near 2750, 4250, 4400, 4950, and 5300 Å at LNT. The 4250 and 4400 Å bands exhibit a weak vibrational structure. When samples are annealed at temperatures above 600 °K, only the 2750 Å band and a wide flat band near 4350 Å remain; it is suggested that they are colloidal bands.Nous avons étudié les centres colorés créés dans LiF, par bombardement, à la température ambiante, avec des particules alpha de 56 MeV et deutons de 28 MeV. La nature et l'évolution des centres présents sont étudiées d'après le spectres d'absorptions optique, obtenus à 300, 77 °K et après des recuits successifs. Cette étude montre qu'en plus des centres F et agglomérats de F il apparait plusieurs centres chargés (F, F, F, F) ainsi que de nouvelles bandes dont les maxima se situent vers 2750, 4250, 4400, 4950 et 5300 Å à 77 °K. Les bandes à 4250 et 4400 Å présentent une faible structure vibrationnelle. Sur les échantillons recuits à des températures supérieures à 600 °K nous n'observons plus que la bande à 2750 Å et une bande très large dont le maximum se situe vers 4350 Å. Nous pensons que ces bandes sont dues à la présence de colloides.
ABSTRACT The low energy cluster beam deposition technique (LECBD) is developed to prepare origina... more ABSTRACT The low energy cluster beam deposition technique (LECBD) is developed to prepare original nanostructured systems from clusters preformed in the gas phase. The nucleation and growth mechanism specific of the cluster deposits is studied Ln view to control the nanostructured morphology of the cluster assembled films, especially for future applications to high areal density devices. Examples of the synthesis and properties of metallic nanostructures as well as covalent ones are presented. In the first case, systems from noble metal clusters (Ag, Au, and AgxAu1-x) and transition metal based clusters (CO, SmCo5) assemblies are studied for their original optical or magnetic properties, respectively. In the second case, covalent se mi conducting films exhibiting specific electronic structures are obtained by Si, C, and SixC1-x cage like clusters (fullerenes and heterofullerenes) depositions.
This paper presents recent results on the preparation and characterization of original magnetic n... more This paper presents recent results on the preparation and characterization of original magnetic nanostructures from nanoclusters preformed in the gas phase. Magnetic binary-clusters (i.e. Co-Sm, Co-Pt, Co-Ag) with rather well controlled sizes, structures and compositions, are prepared in the gas phase using a combined laser vaporization-rare gas condensation source and subsequently deposited at low energy (LECBD : Low Energy Cluster Beam Deposition) on various functionalized substrates to grow cluster-assembled magnetic nanostructures exhibiting specific magnetic properties. Especially a high magnetic anisotropy and consequently a high magnetic blocking temperature compatible with future applications to high density memory devices and spin electronics are expected. In this context of applications, 2D-organized arrays of functionalized binary-cluster assembled dots are prepared by LECBD on FIB-functionalized substrates (FIB: Focussed Ion Beam) with the ultimate objective to reach areal densities in the range of the Tbits/in2.
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Papers by Alain Perez