Compteurs à exoélectrons

On décrit un compteur à faible bruit permettant les études de thermo- et photostimulation, ainsi qu'un compteur pour l'étude « in situ » de catalyseurs de contact

Compteurs à exoélectrons

A description is given of a low noise exoelectron counter for thermo- and photo-stimulation, as well as a counter for « in situ » study of contact catalysts.On décrit un compteur à faible bruit permettant les études de thermo- et photostimulation, ainsi qu'un compteur pour l'étude « in situ » de catalyseurs de contact

Ion flux-film structure relationship during magnetron sputtering of WO

In this work, we have investigated the influence of the magnetic field configuration during magnetron sputtering of WO3 in order to establish the ion flux-film structure relationship. An asymmetric bipolar pulsed DC magnetron sputtering (PDMS) was used with two magnetic field configurations: balanced (BM) and unbalanced (UMB) magnetic configurations. Ion Energy Distribution Functions (IEDFs) of the main ion populations (Ar+, O+) were recorded. The IEDFs are broad with, in addition of the thermalized distribution around 2 eV, two peaks with available ion kinetic energy up to 40–100 eV associated with the positive part of the pulse. Comparing the BM and UBM data, we calculated an increase by a factor of 5 of the ionic current while the average energy per ion was kept constant (~44 eV). X-ray diffraction demonstrates the influence of the magnetic configuration on the coating phase constitution. The films are crystallized in the WO3 monoclinic phase with preferential orientations along the c axis using the BM configuration and along the a axis using the UBM one’s. On the other hand, it has been demonstrated that the grain size increases with the thickness using the BM configuration (up to 18 nm) while it remains constant using the UBM one’s (~7 nm)

Effect of the thickness of reactively sputtered WO 3 submicron thin films used for NO 2 detection

10.1016/j.snb.2012.03.037Tungsten trioxide (WO 3) thin films were prepared by magnetron sputtering onto silicon micro-machined substrates. The dependence of the thin film thickness (varied from 37.5 to 400 nm) on NO 2 gas sensing properties was investigated. The structure, grain size and chemical composition of the deposited WO 3 films have been studied by X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS), respectively. Our results show that the films are formed by grains crystallized in the WO 3 monoclinic phase with preferential orientations along the c axis. The grain size increased with the film thickness. The gas sensing characteristics of the sensors such as sensitivity (normalized response), response time, recovery time and aging were investigated for NO 2 detection and related to the film thickness. For example, a maximum response of 200 was obtained for 37.5 nm thick films operated at 350 °

Optical Diagnostics of RF Argon and Xenon Magnetron Discharges

A comparison of magnetron discharges in Ar and Xe gases with Al and BN targets has shown that a similar electron kinetic is producing about the same quantity of Ar and Xe metastable atoms: $(1{-}3) \times 10^{10}$ cm$^{-3}$ at gas pressures of 25 and 100 mTorr and RF powers, W, from 5 to 50 watts. The electron density is varying as $W^{\frac{1}{2}}$ in the two gases. The sputtering yields of Al and BN targets are lower in Xe than in Ar, by factors of 1.1–1.2 for Al and of 3 for BN.La comparaison de décharges magnétrons dans des gaz d'argon et de xénon, avec des cibles en Al et BN indique que des quantités équivalentes d'argon et de xénon métastables sont produites, à savoir $(1{-}3) \times 10^{10}$ cm$^{-3}$ à des pressions de 25 et 100 mTorr et des puissances RF, W, de 5 à 50 watts. La densité électronique varie comme $W^{\frac{1}{2}}$ dans les deux cas. Les taux de pulvérisation de cibles d'Al et de BN sont plus faibles dans le Xe que dans l'Ar, d'un facteur 1, 1– 1, 2 pour Al et 3 pour BN