Search

Ultra-thin silver films of thicknesses of the order of 10 nm and less were prepared in different ambient conditions (vacuum, Ar, and N2) by pulsed laser deposition on glass and fused silica substrates. The in situ monitoring of electrical resistance of deposited films and optical emission spectroscopy of plasma were implemented as real-time analysis techniques. Change in the growth mechanism of the Ag layer in N2 ambient is expressed by an acceleration of the coalescence process, which shifts the percolation point toward lower mass thicknesses. The films prepared in vacuum and Ar ambient were found to be unstable for a final resistance in the range from 1 to 100 MΩ while the films deposited in N2 revealed stable electrical resistance. The percolation point was further lowered by introducing a sublayer of AgxOy for the film deposited in N2 gas. Based on data provided by AFM, SEM, and spectroscopic ellipsometry, different film formation mechanisms are discussed in relation to surface morphology and optical properties. Optical emission spectroscopy was used to monitor the deposition process and identify the species presented during the deposition process. The energy of the ejected particle is affected by the addition of ambient gas and depends on the properties of the working gas.

A black aluminum (B-Al) film was deposited onto the surface of a stack structure of platinum/Pb(ZrxTi1 − x)O3/platinum (Pt/PZT/Pt) to convert light into a heat variation and the heat variation into a polarization change. A comparison was performed between B-Al/Pt/PZT/Pt and conventional Pt/PZT/Pt structures. An absorbance higher than 95% was measured for the B-Al layer over a large range of wavelengths varying from 350 nm to 1000 nm. The theoretical model shows that heat diffusion was extremely fast through the layers, and the sample holder played a key role in the variation and stabilization of the system temperature. A doubled variation of the polarization was observed when the light was applied onto the surface of the stack structure with stable B-Al on the top. This behavior was interpreted by the larger temperature variations induced under the highly absorptive B-Al layers, in good correlation with the theoretical model prediction based on the heat fluxes in the structures. This result is very promising for possible pyroelectric energy harvesting applications.

International audience; In the present article, we analyse the possibility of sensitizing the 3Pj levels of Pr3+ ion with Eu2+ ion in CaF2 thin film deposited by evaporation. Indeed, the forbidden nature of the 4f-4f transition of Pr3+ ion makes its absorption too weak for thin film applications, while materials doped with the Pr3+-Yb3+ couple are promising candidates for the achievement of efficient down-converter systems and could allow strong reduction of thermalization losses in silicon solar cells.