Etude des mécanismes de collage des microsystèmes lors de la phase de libération (Mise en oeuvre de moyens de prévention)

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Kinetics of thermal desorption using Auger electron spectroscopy application to cesium covered (110) gallium arsenide

We propose a new method for monitoring surface reactions kinetics using Auger Spectroscopy. It allows continuous observations of adsorption and desorption kinetics of an element A on the surface of a substrate B. The apparatus designed for this purpose transforms a standard Auger electron spectrometer into a detector measuring the rate of these surface reactions. We have used this technique to study the thermal desorption of cesium from (110) gallium arsenide. Several binding states are found

Step-driven molecular adsorption of Sb on Si( 111 )

International audienceAdsorption of Sb on a misoriented Si(111) surface is investigated by thermodesorption Auger spectroscopy. The spectra reveal that, in the submonolayer range, new adsorption states appear for the vicinal surface which do not exist for the nominal one. Quenched molecular-dynamics simulations, in which Si and Sb are modeled by many-body tight-binding potentials, allow us to interpret these new states as due to a molecular adsorption at the steps instead of a dissociative one on the terraces

Search for quantum size effects in ultrathin epitaxial metallic films

In order to investigate quantum size effects in ultrathin metal films, tunneling spectroscopy measurements have been performed in the epitaxial CoSi2/Si system, with a metal thickness ranging from 1000 Å down to 35 A, i.e. a few de Broglie wavelengths of electrons in CoSi 2. The resulting spectra show extremely rich sets of features, the origin of which are investigated. The peaks observed at low energy (-100 meV, +100 meV) are thickness independent and attributed to phonon emission by hot electrons. The peaks observed at higher energy (up to 600 meV) are thickness dependent but their physical origin is not yet fully ascertained. The absence of unambiguous electron quantization effects in these epitaxial films is discussed and tentatively attributed to small thickness fluctuations (of the order of a few monolayers), which tend to blur the quantization of the electronic energies

Optical properties of Ge and Si nanosheets - confinement and symmetry effects

Comparison between silicon and germanium quantum sheets has been made regarding their electronic and optical properties. Ab initio calculations have been applied for this purpose by mean of the linearized augmented plane wave method. Quantum confinement is found to shift the band gap of both Si and Ge bulk to the blue, however this upshift depends strongly on the surface orientation. Moreover also the nature of the band gap is related to the surface symmetry: for (100)-oriented films the band gap becomes direct for both semiconductors, whereas the (110)- and (111)-oriented films show a different behavior. In the first case the band gap is direct for Si and indirect for Ge, in the second it is direct for Ge and indirect for Si. Concerning the optical properties, since in the Si films the folded bulk band energies are found to retain their original indirect character, all the Si films have an intense absorption peak only at high energies corresponding to the blueshifted direct band gap of Si bulk. In Ge films the conduction band minimum retains a strong F component. Therefore, dielectric function calculations clearly show that Ge films have a strong optical absorption in the visual energy region. Analysis of the squared optical matrix elements is also presented and the data are compared to the results for GaAs. (C) 2003 Elsevier Science B.V. All rights reserved