Nanoscale morphology tuning of mesoporous Ge: electrochemical mechanisms

International audienceThe extended analysis of influence of the surface hydrogen passivation degree on morphology of mesoporous Ge (PGe) formed by Bipolar Electrochemical Etching technique is reported. It is shown that the high degree of the surface passivation results in formation of the isotropic sponge-like PGe layers, whereas at low degree of the surface passivation the crystallographic “pine-tree-like” pores are obtained. The intermediate passivation results in the “fish-bone” morphology. It should be noted that the last two morphologies were never obtained before and are unique to mesoporous Ge. The electrochemical reactions taking place on Ge during BEE process are identified by analyzing the evolution of the surface potential during the BEE process; the results were interpreted similarly to the cyclic voltametry data. Finally, a general electrochemical model describing the pore formation with different morphologies depending on the surface passivation degree is introduced

Monte Carlo simulations of phonon transport in nanoporous silicon and germanium

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Monte Carlo simulations of phonon transport in nanoporous silicon and germanium

International audienceHeat conduction of nanoporous silicon and germanium thin films is studied thanks to a statistical approach. Resolution of phonon Boltzmann transport equation is performed with a Monte Carlo technique in order to assess thermal conductivity. Sensitivity of this latter property with respect to parameters such as phonon mean free path and characteristics of the pores ( distribution, size, porosity) is discussed and compared to predictions from analytical models. Results point out that thermal properties might be tailored through the design of the porosity and more specifically by the adjustment of the phonon-pore mean free path. Finally, an effective medium technique is used to extend our work to multilayered crystalline-nanoporous structures. Results show that ought to pore scattering, a diffusive Fourier regime can be recovered even when the film thickness is below the bulk limit

Realisation of Self-Aligned Thin Film Si Solar Cell with Interdigitated Structure

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Realisation of Self-Aligned Thin Film Si Solar Cell with Interdigitated Structure

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Copper light induced plating on silver screen-printed contacts of silicon solar cells

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Mesoporous Germanium formed by bipolar electrochemical etching

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