Investigation of a single Ge dots layer and its evolution upon oxidation by spectroscopic ellipsometry

We present an ellipsometric investigation of a layer of Ge dots embedded in Si. Through dielectric function analysis, it is found that the layer containing Ge dots is actually constituted of a Si0.85Ge0.15 alloy containing Ge richer inclusions characterised by an additional contribution around 2.98 eV. After oxidation of the Si layer, the SiGe alloy is pushed into the Si substrate by the growing oxide and the Ge rich inclusions are no longer detected

Nouveaux matériaux pour des couches minces diélectriques à bas indice de réfraction (application aux traitements antireflet sur verres ophtalmiques)

PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Spectroscopic ellipsometry study of a self-organised Ge dot layer

We report on the determination of the dielectric function of a Ge dot layer obtained by epitaxial growth on Si(001) in the presence of Sb as surfactant and capped by Si. After growth, spectroscopic ellipsometry reveals a SiGe alloy containing Ge rich regions. After etching the Si cap, the dielectric function of the Ge rich regions exhibits critical points located at 2.92, 3.65, and 4.25 eV. It is shown that this dielectric function does not correspond either to an alloy or to bulk Ge, and is affected by confinement

Adsorption et condensation de gaz dans des couches minces diélectriques mésoporeuses suivies par ellipsométrie

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Etude par ellipsométrie spectroscopique et photoluminescence des effets de taille sur les propriétés optiques de nanocristaux de Si dans SiO2 et SiO2 dopé Er. (rôle des nanocristaux de Si dans l' excitation de la luminescence des ions Er.)

PARIS-BIUSJ-Thèses (751052125) / SudocSudocFranceF

Etude des propriétés optiques de nanoparticules de silicium et de leur interface avec une matrice de silice par ellipsométrie et spectroscopie de déflexion photothermique

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Spatially Resolved EELS Fine Structures at a SiO 2

$\rm SiO_2/TiO_2$ multilayers stacks used in optical coatings have been studied by Electron Energy Loss Spectroscopy (EELS). The line-spec trum mode has been used: the incident electron probe of the STEM is scanned under digital control on the specimen surface in the direction perpendicular to the layers, while the whole spectrum is acquired. The selected energy range contains Ti $\rm L_{23}$ and O K edges, in order to study the evolution of the fine structures visible on these edges. Every experimental spectrum is then fitted with a linear combination of the two reference spectra ($\rm TiO_2$ and $\rm SiO_2$) extracted from the same sequence. It is possible to identify in the neighbourhood of the interface some EELS fine structures which cannot be fitted to a combination of reference spectra, but are representative of hybrid environments, such as Si-O-Ti in the present study. A quantitative analysis of the changes in different fine structures on the titanium and oxygen edges enables to clearly discriminate different levels of interdiffusion at the boundary

Reactivity of 3D hexagonal mesoporous silica films to environment studied by infrared ellipsometry

This paper discusses the origin of the increase of the refractive index of 3D hexagonal mesoporous silica films during aging in air. Indeed spectroscopic ellipsometric measurements in the visible range show a strong increase of refractive index from 1.25 to 1.46, without significant thickness variation. Analysis of the infrared ellipsometry spectra allows us to conclude that the silica skeleton as well as the pore volume fraction remain unmodified during aging, whereas an important hydrocarbon and water contamination of pores is observed. This contamination can be accounted for by an increase of the pore refractive index (from 1 to 1.44). This work also allows to point out that the pore volume fraction cannot be accurately determined from the value of the refractive index in the visible range without the knowledge of the skeleton refractive index and of the pore content

In-situ control of SiOx stoechiometry by spectroscopic ellipsometry

International audienceThis paper presents a study on the growth of SiOx thin films deposited by electron gun evaporation of SiO under O2 reactive atmosphere. The composition x of the films was determined by spectroscopic ellipsometry using the random bonding model (RBM) provided that the parameters used in the original model of Aspnes and Theeten [J. Appl. Phys. 50 (1979) 4928] were adapted to the growth conditions. The composition depended mainly on the flux ratio of the species arriving on the surface. This model had to be slightly modified to take into account the composition of the films evaporated without oxygen, exhibiting a x value of 1.2 instead of 1, and the incorporation of O2 in the growing film

Infrared ellipsometric study of SiO2 films: relationship between LO mode frequency and porosity

A method for evaluating the pore volume fraction of silica films for different pore connectivities is presented. A series of SiO2 films, evaporated by electron gun with or without ion bombardment, have been studied using visible and infrared ellipsometry. The TO and LO mode frequencies are deduced from the dielectric function calculated from infrared ellipsometric data. The study of both TO and LO mode frequencies is shown to bring independent information on the film microstructure. The TO mode frequency (near 1075 cm−1) varies mainly with the density of the silica matrix. On the other hand, variation in the LO mode frequency (near 1245 cm−1) is mainly due to changes in porosity. In the case of films with pores largely connected, the evaluation of the pore volume fraction from the LO frequency is compared to that obtained from the analysis of the large water absorption band near 3300 cm−1 (H–OH and Si–OH stretching absorption band)