High temperature micro-hotplate

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The objective of this PhD thesis is to develop a microfluidic chip platform for real-time, multidimensional characterization of biological samples and, eventually, calorimetric measurements at the single-entity level. The developed devices are piezoelectrically transduced single- and double-clamped beams with embedded microchannels, commonly known as Suspended Microchannel Resonators (SMRs). Their operating principle relies on the flow of samples through the microchannels and on the real-time monitoring of

Perovskite-Si tandem solar cells are a leading pathway to surpass the single-junction efficiency limit of crystalline silicon photovoltaics. Their realization requires integrating many functional layers, making reproducible high-performance fabrication and systematic analysis challenging. This thesis investigates the design, fabrication, and characterization of monolithic solution-processed perovskite-Si tandems, combining process development with quantitative modeling to establish practical guidelines for

While low hole mobilities limit the current collection and efficiency of hydrogenated amorphous silicon (a-Si:H) photovoltaic devices, attempts to improve mobility of the material directly have stagnated. Herein, we explore a method of utilizing nanostructuring of a-Si:H devices to allow for improved hole collection in thick absorber layers. This is achieved by etching an array of 150 nm diameter holes into intrinsic a-Si:H and then coating the structured material with p-type a-Si:H and a conformal zinc oxi

The residual stress and buckling patterns of free-standing 8?mol.% yttria-stabilized-zirconia (8YSZ) membranes prepared by pulsed laser deposition and microfabrication techniques on silicon substrates are investigated by wafer curvature, light microscopy, white light interferometry, and nanoindentation. The 300?nm thin 8YSZ membranes (390?mu m?x?390?mu m) deposited at 25?degrees C are almost flat after free-etching, whereas deposition at 700?degrees C yields strongly buckled membranes with a compressive str

We report on the fabrication and characterization of high-temperature Pt-TSVs. A LPCVD silicon nitride passivation layer was implemented to protect the TSVs from oxidation during high-temperature treatments and wet HF-based post-processing steps, the later being widely used for the release of MEMS mechanical structures. An ohmic contact between the TSV metallization and a silicon device layer was created and maintained, during and after high-temperature treatments. These “via first” TSVs were able to withst

High band gap thin film silicon solar cells are of high interest for the use as top cell in triple junctions solar cells. Protocrystalline silicon, in the transition phase between amorphous and microcrystalline silicon, is such a high band gap material. During this project, protocrystalline intrinsic layers have been developed and optimized in p-i-n single junction solar cells by plasma-enhanced chemical vapour deposition (PECVD) in a new multi-chamber deposition system. In the first series, cells and layer

Silicon heterojunction solar cells have high open-circuit voltages thanks to excellent passivation of the wafer surfaces by thin intrinsic amorphous silicon (a-Si:H) layers deposited by plasma-enhanced chemical vapor deposition (PECVD). By using in-situ plasma diagnostics and ex-situ film characterization, we show that the best a-Si:H films for passivation are produced from deposition regimes close to the amorphous-to-crystalline transition. Based upon this finding, layers deposited in a large-area very hig

High reflectivity is essential when a metal is used as back contact and reflector in thin-film silicon solar cells. We show that thermal annealing at 150 °C improves the reflectivity of silver films deposited by sputtering at room temperature on nanotextured substrates. The annealing provokes two interlinked effects: rearrangement of the silver layer with a modification of its morphology and an increase of up to 42% in the grain size of the polycrystalline film for the preferential orientation as measured b

This paper presents the state-of-the-art of nanostencil as a direct and local patterning method. Stencil lithography is a high-resolution shadow mask technique that allows structuring surfaces without using the harsh process steps typically associated with photolithography (solvents, high temperature baking, etc.). Our work has concentrated on studying the technique and maximizing its potential in terms of resolution, scalability to full wafer, and applicability to various material systems. We found solutio

A new approach to reduce phosphorous contamination in the intrinsic layer during the deposition of amorphous silicon (a-Si:H) nip solar cells prepared in single-chamber reactors is presented. This novel process consists of a hydrogen etching plasma performed after the n-layer deposition, which prevents a recycling of phosphorous from the reactor walls when exposed to a hydrogen-rich plasma during the subsequent i-layer deposition. The implemented process reduces the phosphorous cross-contamination in the i-

The performances of thin film silicon solar cells are reported for the use of increasingly rough zinc-oxide (ZnO) front electrodes. Experimental results show that textured substrates favor increased light trapping but also the local creation of undesired current drains, degrading the electrical performance of the cells. While an appropriate plasma treatment of the ZnO surface and a high silicon material quality are required to decrease the density of such current drains, doped nano-crystalline silicon oxide

The requirements for a micromorph tandem cell front transparent conductive oxide (TCO) are multiple. This essential layer needs a high transparency, excellent conduction, strong light scattering into silicon and good surface morphology for the subsequent growth of silicon cells. These parameters are all linked and trade-offs have to be found for optimal layer. The optimum combination, taking into account current achievable materials properties, is still unclear. Concerning transparency, we study here the im

The development of a particular etching recipe involving two sequences of a Deep Reactive Ion Etching followed by an isotropic etching step for the realization of 3D stacked arrays of fins and nanowires on bulk silicon is reported. Such a recipe can be used among the new processes and designs developed to control the shape and formation of such 3D structures. Applications in microelectronics (stacked field effect transistors) and microsystems (arrays of MEMS resonators and photonic structures) are foreseen.

The endeavour to develop nanodevices demands for patterning methods in the nanometer scale. The continuous improvement in lithography methods based on deep UV (DUV), X-ray, or electron beam exposure allow for further progress in integrated circuit hardware manufacturing for the coming years. To bring nanodevices to the market, however, there is a need for fast, low-cost replication nanopatterning methods. In addition, an increased flexibility of the nanopatterning methods is important for the engineering of

Sub-micron lithography processes are continuously optimized for semiconductor products where the enormous market potential justifies investment in advanced methods and extremely sophisticated equipment. Due to the extreme process costs and due to the limited process versatility in terms of substrates, processing and materials, these high-end methods can not be applied for the engineering of multi-material and multifunctional nano/micro-electro-mechanical systems (NEMS/MEMS), such as polymer-based electronic

Pb(Zr-x, Ti1-x)O-3 (PZT) piezoelectric thin films are of major interest in MEMS technology for their ability to provide electro-mechanical coupling. In this work, the effective transverse piezoelectric coefficient e(31,f) of sol-gel processed films was investigated as a function of composition, film texture and film thickness. Dense, textured and crack-free PZT films have been obtained on silicon substrates up to a thickness of 4 mum. Crystallization anneals have been performed for every 0.25 mum. Nucleatio

In the search for a good dimensionally stable anode-type electrode, p-silicon (1-3 mW cm) has been chosen as the substrate material due to its high anodic stability and its reasonable cost compared to titanium and tantalum. Several p-Si/IrO2 electrodes have been prepd. by thermal decompn. at different temp. The effect of prepn. temp. on the morphol. and electrochem. properties has been investigated by SEM anal., X-ray diffraction, and cyclic voltammetry in 1 M HClO4 showing that p-Si/IrO2 prepd. at 450 DegC

Silicon and silicon nitride surfaces have been successfully terminated with carboxylic acid monolayers and investigated by atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). On clean Si surface, AFM showed topographical variations of 0.3-0.4 nm while for the clean Si3N4 surface the corrugation was around 3-4 nm. After material deposition, the corrugation increased in both samples with a value in topography of 1-2 nm for Si and 5-6 nm for Si3N4. The space distribution of specifi

Zinc oxide (ZnO) is a material that belongs to the family of Transparent Conductives Oxides (TCO). Its non-toxicity and the abundant availability in the Earth's crust of its components make it an ideal candidate as electrical transparent contact for thin-film amorphous and/or microcrystalline silicon solar cells. The Low-Pressure Chemical Vapour Deposition (LP-CVD) method allows one to obtain rough ZnO layers, which can effectively scatter the light that passes through them. This high scattering capacity in

We report on a 2×2 SOI switch, based on the plasma dispersion effect, reaching 5 MHz of switching frequency. Measured insertion losses, extinction ratio and crosstalk at 1300 nm and 1550 nm are presented and discussed.

High temperature micro-hotplate

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Piezoelectric Suspended Microchannel Resonators for Calorimetry

Design, fabrication and characterization of monolithic perovskite-silicon tandem solar cells

Nanohole Structuring for Improved Performance of Hydrogenated Amorphous Silicon Photovoltaics

Residual Stress and Buckling Patterns of Free-standing Yttria-stabilized-zirconia Membranes Fabricated by Pulsed Laser Deposition

Platinum TSVs for High-Temperature Processing and Operation of Microsystems

Development of high band gap protocrystalline material for p-i-n thin film silicon solar cells

21% efficiency silicon heterojunction solar cells produced with very high frequency PECVD

Highly reflective nanotextured sputtered silver back reflector for flexible high-efficiency n–i–p thin-film silicon solar cells

Advances in Nanostenciling: resistless nanopatterning enables new applications

Reduction of the phosphorous cross-contamination in nip solar cells prepared in a single-chamber PECVD reactor

Low-conductivity doped layers for improved performance of thin film silicon solar cells on highly textured substrate

Transparent conducting oxide electrodes requirements for high efficiency micromorph solar cells

3D stacked arrays of fins and nanowires on bulk silicon

High-throughput surface patterning with wafer-sized stencils fabricated by a DUV/MEMS process

MEMS based nanopatterning

{100}-textured, piezoelectric Pb(Zr-x Ti1-x)O-3 thin films for MEMS: integration, deposition and properties

Dimensionally Stable Anode-Type Anode Based on Conductive p-Silicon Substrate

AFM and SNOM characterization of carboxylic acid terminated silicon and silicon nitride surfaces

L'oxyde de zinc par dépôt chimique en phase vapeur comme contact électrique transparent et diffuseur de lumière pour les cellules solaires

5 MHz 2×2 optical switch in silicon on insulator technology using plasma dispersion effect