Eau-forte | EPFL Graph Search

vignette|Rembrandt, La Pièce aux cent florins, eau-forte. L’eau-forte est un procédé de gravure en taille-douce sur une plaque métallique à l’aide d’un mordant chimique (un acide). L’artiste utilisant l’eau-forte est appelé aquafortiste. À l’origine, l’eau-forte était le nom donné à l’acide nitrique. Aujourd’hui, l’acide nitrique est remplacé par des mordants moins toxiques, tel le perchlorure de fer. L’eau-forte est un procédé de taille indirecte (par morsure du métal par un acide), par opposition à la taille directe (à l’aide d’outils, tels burin ou pointe sèche). Parmi les différents procédés d’eaux-fortes, on trouve l’aquatinte, la gravure au lavis ou la manière de crayon. Toutes désignent une technique de gravure où l’image est creusée sur une plaque de métal à l’aide d’un acide. Elles diffèrent en revanche par les outils ou vernis à graver utilisés. Le principe est simple : sur la plaque de métal préalablement recouverte d’un vernis à graver, l’artiste dessine son motif à la

Evaluation of Cost-Effective Technologies for Highly Efficient Silicon-Based Solar Cells

Luca Gautero

The work underscores the feasibility of highly efficient silicon solar cell structures manufactured with high throughput machines. The main challenge consists in the implementation of more performant structures of intrinsic higher complexity. These structures are meant to be fabricated within similar constraints on time and on cost as for conventional devices of industrial manufacture. Achievements in this direction foster larger economical deployment of this kind of renewable energy. The structure chosen for the implementation of "high efficiency" concepts requires an advanced machining of the silicon substrate. Etching techniques, dielectric coating preparations, and metal to semiconductor contact formation were evaluated for their integration in a complete silicon solar cell fabrication sequence. These sequences were later tested to gain knowledge regarding the effects of the aforementioned advanced processing. Prototypes were created using the fabrication sequence. They were analysed to acquire a further understanding of the advanced processing influences. Statistical interpretation of the data obtained was used to support physical interpretation of the observed phenomena. For one particular implementation of a surface passivation (floating junction passivation) an attempt of modelling aiming to unveil its specific dynamics is reported. A resulting solar cell concept compatible with high throughput equipment achieved a certified efficiency of 18% (VOC = 635 mV, JSC = 37.3 mA/cm2, FF = 76 %) on substrate with a reduced thickness (120 µm). The resulting sequence prepares the back surface with a thermal oxidation for passivation purposes and with a laser technique to locally contact the bulk. The thickness is compatible with the intent of cost reduction through the decrease in material consumption. Other approaches performed on the same substrate achieved 17.1% efficiency (VOC = 617 mV, JSC = 36.1 mA/cm2, FF = 75 %). In this case the passivation was achieved with deposited dielectric layers on the back surface. Furthermore, the investigated dynamics of the floating junction passivation allows for better insight into its traits. The proposed solution has an interesting ratio of efficiency versus costs. The general consequence is a higher market appeal of this particular renewable source on the energy market. The study on the floating junction passivation allows a better exploitation of this particular implementation towards more performant silicon solar cells.

EPFL2010

Method for fabricating micromirror for barcode reader, involves forming holes having diameter less than width of arms on both side of micromirror and wafer and on edges of region separating wafer and micromirror by etching arms

Nicolas Abelé, Faouzi Khechana, Philippe Renaud

A method for fabricating a micromirror in a wafer, including the steps of: depositing and etching layers forming two arms; etching the wafer such that in the back face only a thin portion of the wafer remains in the region of formation of the micromirror and the arms; performing an anisotropic etch, such that the thin portion remains only in the areas of the micromirror and the arms; and performing an isotropic etch to remove the thin portions under the arms, the etching step for forming the arms being performed following their shape and so as to form holes traversing the arms, the holes being positioned at edges of the region separating the micromirror and the wafer on both the side of the micromirror and the side of the portions of the wafer remaining after the anisotropic etching step. The invention also concerns the micromirror.

2010

Study on the Performances of AlScN based SAW/BAW Hybrid Resonators A Parametric Analysis of Acoustic Wave Resonators with Large Figure of Merit

Guilain Lionel Germain Lang, Luis Guillermo Villanueva Torrijo, Soumya Yandrapalli

In this study, we analyze a 3rd type of FBAR's fundamental mode by finite element method. We show the importance of the substrate's wave velocity and conductivity on the electromechanical coupling efficiency. Then we demonstrate that etching traditional SAW sensors in between its electrodes is an effective solution to increase its performances. Finally, the finite device simulations of optimized geometries demonstrate the full potential of AlSc(0.4)N based SAW/BAW hybrid resonators: an impedance response free of spurious modes and large figure of merit (k(t)(FD, 1.35GHz)(2) = 2.48%).

IEEE2021

Evaluation of Cost-Effective Technologies for Highly Efficient Silicon-Based Solar Cells

Luca Gautero

EPFL2010