Aurélien Gohier

High-Rate Capability Silicon Decorated Vertically Aligned Carbon Nanotubes for Li-Ion Batteries

The concept of a hybrid nanostructured collector made of thin vertically aligned carbon nanotubes (CNTs) decorated with Si nanoparticles provides high power density anodes in lithium-ion batteries. An impressive rate capability is achieved due to the efficient electronic conduction of CNTs combined with well defined electroactive Si nanoparticles: capacities of 3000 mAh g−1 at 1.3C and 800 mAh g−1 at 15C are achieved.

All-printed infrared sensor based on multiwalled carbon nanotubes

This contribution deals with all-printed infrared sensors fabricated using multiwalled carbon nanotubes deposited on a flexible polyimide substrate. A high responsivity of up to 1.2 kV/W is achieved at room temperature in ambient air. We evidence a strong dependence of the device transduction mechanism on the surrounding atmosphere, which can be attributed to bolometric effect interference with water molecule desorption upon irradiation.

Effect of Lithiation Potential and Cycling on Chemical and Morphological Evolution of Si Thin Film Electrode Studied by ToF-SIMS

Si thin films obtained by plasma enhanced chemical vapor deposition (PECVD) were used to investigate chemical and morphological modifications induced by lithiation potential and cycling. These modifications were thoughtfully analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling, which allows to distinguish the surface and bulk processes related to the formation of the solid electrolyte interphase (SEI) layer, and Li-Si alloying, respectively. The main results are a volume expansion/shrinkage and a dynamic behavior of the SEI layer during the single lithiation/delithiation process and multicycling. Trapping of lithium and other ions corresponding to products of electrolyte decomposition are the major reasons of electrode modifications. It is shown that the SEI layer contributes to 60% of the total volume variation of Si electrodes (100 nm). The apparent diffusion coefficient of lithium (DLi) calculated from the Ficks second law directly from Li-ion ToF-SIMS profiles is of the order of ∼5.9 × 10(-15) cm(2).s(-1). This quite low value can be explained by Li trapping in the bulk of electrode material, at the interfaces, continuous growth of the SEI layer and increase of SiO2 quantity. These modifications can result in limitation the ionic transport of Li.

Cup‐Stacked Carbon Nanotube Schottky Diodes for Photovoltaics and Photodetectors

High performance optoelectronic devices based on cup-stacked carbon nanotubes are realized. Based on a Schottky barrier model, rectifying behaviors and high photoresponse are observed by using growth catalysts as nanoscale electronic contacts. Similar performances are also obtained and furthermore tuned by using nanotube’s defective surface as effective decoration sites transforming nanotubes resistors into Schottky diodes.

The OPTHER project: Progress toward the THz amplifier

This paper describes the status of the OPTHER (OPtically driven TeraHertz AmplifiERs) project and progress toward the THz amplifier realization. This project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within this project is a consolidation of efforts at the international level from the leading scientific and industrial European organizations working with vacuum electronics.

European research on THz vacuum amplifiers

The OPTHER (OPtically Driven TeraHertz AmplifiERs) project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within this project is a consolidation of efforts at the international level from the main players of the European research, academy and industry in vacuum electronics. This paper describes the status of the project and progress towards the THz amplifier realization.

The organization of carbon nanotube and silicon nanowires using lateral-type porous anodic alumina

We successfully synthesized organized Carbon nanotubes (CNTs) and Silicon Nanowires (SiNWs) arrays using LPAA. This approach can yield very dense assemblies of nano-objects with a planar-type organization compatible with existing tools inherited from advanced microelectronic processes and adapted to electronic devices as field effect transistors, interconnects, sensors, etc. CNTs/SiNWs were grown using Hot-filament Chemical Vapor Deposition (HFCVD) within lateral-type porous anodic alumina. We demonstrate that the pulsed electrodeposition of metal nanoparticles to be further used as catalysts inside the membranes requires specific thinning and pore widening process to remove the alumina barrier layer located at the bottom of the pores. The growth of CNTs was found to strongly depend on the electrodeposition conditions as well as on the CVD parameters. In addition, we found that introducing atomic hydrogen (generated using a hot-wire) as etching agent was essential to prevent parasitic carbon/silicon deposition on the surface of PAA or on the wall of pores and to improve CNTs/NWs growth. Such organized CNTs/SiNWs arrays are very promising as advanced microelectronic devices and their potentiality for photosensing applications were investigated.

Towards a THz backward wave amplifier in European OPTHER project

Within the EC funded international project OPTHER (OPtically Driven TeraHertz AmplifiERs) a considerable technological effort is being undertaken, in terms of technological development, THz device design and integration. The ultimate goal is to develop a miniaturised THz amplifier based on vacuum-tube principles The main target specifications of the OPTHER amplifier are the following: - Operating frequency: in the band 0.3 to 2 THz - Output power: > 10 mW ( 10 dBm ) - Gain: 10 to 20 dB. The project is in the middle of its duration. Design and simulations have shown that these targets can be met with a proper device configuration and careful optimization of the different parts of the amplifier. Two parallel schemes will be employed for amplifier realisation: THz Drive Signal Amplifier and Optically Modulated Beam THz Amplifier.

Two anode materials for Li ion batteries with different reaction mechanisms : silicon nanowires and ruthenium nitride thin film

Research carried out in our laboratory is devoted to new materials of electrodes for lithium ion batteries. This presentation focuses on anodic materials, especially on two examples, silicon and ruthenium nitride. In both cases, electrochemical properties and structural evolutions are correlated in order to optimize performances in terms of specific capacity, cyclability and rate capability.