Contribution à l'étude de la conduction électrique des couches métalliques minces aux basses températures

The data described in this paper have been obtained with Mostovetch, Feldman et Romand at the Laboratory of Prof. E. Darmois during the last years. The paper contains the following main experiments : 1) experimental methods for obtaining stable and clean metallic layers on glass, a few atoms thick. 2) Measurement of the D C resistance of these layers down to 4,2° K. The results concern : 1) the variation with the temperature, implying a small activation energy; 2) effect of adsorbed gases, which decrease the resistance. 3) effect of applied potential expressed by a linear relation between log R(F) et F½, F being the average field ; 4) effect of a dielectric layer on the field effect ; 5) field effect for low fields and for strong fields (saturation). The origin of the observed phenomena are briefly discussed. The activation energy may be due to the potential wall between particles or atomes; the field effect is then a modified form of the Shottky effect ; the adsorbed gases may reduce the height of the wall. The small value of the activation energy is possibly due to the fact that the electron never escape far enough from the particles. Another origin for the activation energy is connected with the surface states and the possible gap between Brillouin zones in a 2 dimensional array

Instruments et techniques pour l'ultraviolet lointain au C. N. R. S. -Bellevue

This paper describes the work done recently at the C. N. R. S. Bellevue on instrumentation problems and techniques in the vacuum ultraviolet. The application of the vacuum spark emission spectrum in the far ultraviolet to the spectrochemical analysis of metalloids in steel samples has been developed, and presently the direct reading instrument is able to measure the concentration of C, S, P, Si, As, and also of nitrogen and oxygen. A refined calculation of a focalisation mechanism for a normal incidence grating monochromator has led to an instrument of very compact design. Attempts were directed towards the study of polarized light in far U. V. and results have been obtained using stacked fluorite plates. A linear dichroïsm effect has been observed on thin samples of calcite in the region 1660–1900 Å. The study of absorption spectra in the extreme ultraviolet, using the continuous spectrum emitted by the vacuum spark as a background, allowed the observation of a particular transition mechanism in the case of xenon: the electron jump occurs between a level from an internal shell to upper levels beyond the external shell. </jats:p

Spectre d'absorption ultraviolet du gaz chlorhydrique et courbe d'énergie potentielle de l'état excité de la molécule ClH

Étude expérimentale et théorique de la variation, dans l'ultraviolet (ν allant de 44 000 à 47 000 cm-1) du coefficient d'extinction moléculaire ε en fonction du nombre d'onde ν dans Cl H pur gazeux. L'absorption spécifique ne dépend ni de la pression (ce qui montre qu'il n'y a pas association), ni de la température entre — go et + 20° C : le niveau vibratoire fondamental est donc seul excité. La courbe de log ε en fonction de ν est une droite. Calcul, à partir des résultats expérimentaux, de la courbe d'énergie potentielle de l'état excité de Cl H. Il faudrait, pour arriver à des résultats plus complets, connaître plus exactement le spectre d'absorption dans l'ultraviolet de Schumann

Application des couches métalliques minces à la réalisation de résistances électriques en particulier de résistances électriques de valeurs élevées

Conditions are described under which thin metallic layers on glass may be used as good resistors. The importance of refractory and noble metal is shown. Some data are given on the properties of thin layers resistors : temperature coefficient (which may be widely varied) ; voltage coefficient (almost negligible) power dissipation ; stability (order of 0,1 %). Are presented some practical devices for making different types of resistors by evaporation under vacuum : In order to use a thicker layer long et narrow films are employed ; procedures in order to make layers of such a shape are given. A brief description is presented of an interrupted vacuum arc where the evaporated metal is ionised and may be concentrated by an electric field on the usefull area; this arc is especially interesting for the practical evaporation of high melting metals

Étude de la conduction électrique des couches métalliques minces en haute fréquence

The electrical resistance of thin films evaporated on glass decreases with increasing frequencies ; the variation is more important at very low temperatures. This effect is accounted for the. existence of capacities between aggregates. This measures at high frequencies can give informations about metallic conduction within grains, while measurements with direct current inform about the work fonction of electrons