Etude par photoémission de la passivation de GaAs en plasmas multipolaires d'azote et d'hydrogène

La passivation des matériaux III-V demeure un défi aux physiciens des surfaces. Un processus de passivation faisant intervenir une étape de nettoyage et la formation d'un nitrure en plasma a été proposé. Dans cette revue des résultats obtenus au LEP, nous détaillerons particulièrement l'interaction entre le plasma d'hydrogène ou le plasma d'azote et la surface de l'échantillon. Le plasma multipolaire utilisé produit des ions peu énergétiques et une forte proportion d'espèces atomiques. Nous concentrons notre investigation à l'étude des liaisons chimiques observées par photoémission et aux propriétés électriques de la surface. Les caractéristiques électriques sont étudiées in situ par photoémission de niveaux de coeur. L'attention sera focalisée sur la présence d'arsenic « élémentaire » et sur la désoxydation de la surface

Sequential environmental stresses tests qualification for automotive components

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Electronic structure and pairwise interactions in substoichiometric transition metal carbides and nitrides

In substoichiometric transition metal carbides and nitrides crystallizing with the NaCl structure, the vacancies, which appear on the metalloid FCC lattice only, may order under some conditions. The corresponding long range ordered phases are analogous to those predicted, for FCC substitutional alloys, by theoretical calculations using pair interactions limited to first and second neighbours (V1, V2). We show here that the ordering energy of these compounds can be expanded in terms of pairwise interactions calculated from the electronic structure of the disordered state and that this expansion can be limited to a good accuracy to first and second neighbours. From these calculated pair interactions we then derive a theoretical (V1, V2) diagram in which the domains of existence of ordered carbides and nitrides are well separated; more precisely carbides exist in the region (V2 > 0, V2 >> V1) whereas nitrides are found for (V1 ≳ V2, V1 > 0), in fair agreement with experiments.Dans les carbures et nitrures sous-stoechiometriques de métaux de transition de structure NaCl, les lacunes qui apparaissent sur le sous-réseau CFC occupé par les atomes de carbone (azote) peuvent s'ordonner sous certaines conditions. Les phases ordonnées observées sont les memes que celles que prévoient, pour les alliages CFC de substitution, des calculs théoriques utilisant des interactions de paires limitées aux premiers et seconds voisins (V1 , V2). Nous montrons ici que l'énergie d'ordre de ces composés peut s'exprimer comme une somme d'interactions de paires, calculées à partir de la structure électronique de l'état désordonné, et limitées aux premiers et seconds voisins. Nous en déduisons un diagramme (V1, V2) calculé, dans lequel les domaines d'existence des carbures et nitrures sont bien séparés : plus précisément les carbures existent dans la région (V2 > 0, V2 ≽ V1) tandis qu'on trouve les nitrures pour (V1 ≳ V2, V 1 > 0) en bon accord avec les observations expérimentales

Sequential environmental stresses tests qualification for automotive components

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Investigation of point defect generation in dry etched InP ridge waveguide structures

International audienceWaveguides engraved in InP by dry etching, reactive ion etching and inductively coupled plasma ͑ICP͒, were studied by cathodoluminescence. The dry etching processes were found to induce nonradiative recombination centers, which reduce the luminescence emission from the ridge structures. In addition, the ICP process introduced intrinsic defects, probably In vacancy related defects, which were generated at the dielectric cap/InP interface at the ridge to

Package delamination as indicator of ball bond lift: New diagnostic methodology

International audienceThe components used in the automotive environment are subjected during their lives to various environmental combined stresses. The predominant failure mechanism at the package level due to these combined stresses is the ball bond lift. The failure is due to the combination of metallurgical effects, Such as the intermetallic (IMC) Au-Al thickness growth, widening of Kirkendall voids and mechanical ones as a consequence of the delamination increase. The purpose was to detect the potential weaknesses of die to leads connections. The Usual methods described by the automotive qualification standard AEC-Q100 are not Sufficient to follow the temporal evolution Of the degradation. For this reason, we propose, in addition to the existing, methods, a new diagnosis reliability methodology, which consists to use the delamination monitoring as an indicator of potential assambly weaknesses

Effect of ion bombardment on the structural and optical properties of TiO 2 thin films deposited from oxygen/titanium tetraisopropoxide inductively coupled plasma

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Local stress measurements in laterally oxidized GaAs/AlxGa1-xAs heterostructures by micro-Raman spectroscopy

Lattice deformation induced in surface GaAs layers by the selective lateral oxidn. of buried AlxGa1-xAs layers was detd. from the energy shift of the GaAs phonon line in Raman spectra excited with a focused laser beam. The procedure included a correction for the laser beam induced heating effects. The surface GaAs layer was found under small tensile stress in the oxidized regions of the samples with respect to the unoxidized regions. The deformation is 8 * 10-4 and is the same, within exptl. error, for heterostructures incorporating pure AlAs layers or Al0.98Ga0.02As. Strong differences in Raman efficiency, as well as in photoluminescence efficiency, were obsd. for different samples, which are discussed in terms of the GaAs/oxide interface nonradiative recombination efficiency. [on SciFinder (R)

Influence of technological parameters on the behavior during aging at high temperature of various packages, in the automotive environment

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