SiGe epitaxy on a 300 mm batch furnace

This work reports the feasibility of silicon and silicon germanium epitaxy using an ASM A412(TMa) LPCVD all quartz, hot wall, vertical batch furnace reactor using 100 wafer product loads. The very same furnace can be used for 25 wafer and 200 wafer load size, without any hardware changes, dependant on production needs. Following this approach a significant cost reduction for epitaxy in 300 mm high volume manufacturing is possible and enables new applications. The native oxide of the substrate was removed by wet chemical cleaning with time coupling of less than 1 h and subsequent in-situ low pressure hydrogen anneal prior to Si or SiGe deposition. The epitaxial layers were grown using silane and germane. The Si and SiGe layers have been characterized with ToFSIMS, XRD, Raman, AFM and TEM confirming excellent crystalline quality, layer thickness and within wafer SiGe stoichiometry uniformity.     

Bridging at the Nanometric Scale in 2.5D Cf–SiC Composites

This short paper presents the matrix microcrack bridging at a nanometric scale which was evidenced during creep tests of 2.5D C_f–SiC composites. It also shows the importance of the investigations of mechanical behavior of composite materials at all the different scales: from the macroscopic down to the nanoscopic one.     

Predictive autonomic transmission for low-cost low-margin metro optical networks

Photonic Network Communications - Low-cost low-margin implementation plays an essential role in upgrading optical metro networks required for future 5G ecosystem. In this regard, low-resolution...     

Implementation of Thermoelectric Generators in Airliners for Powering Battery-Free Wireless Sensor Networks

In recent years, wireless sensor networks (WSN) have been considered for various aeronautical applications to perform sensing, data processing and wireless transmission of information, without the need to add extra wiring. However, each node of these networks needs to be self-powered. Considering the critical drawbacks associated with the use of electrochemical energy sources such as narrow operating temperature range and limited lifetime, environmental energy capture allows an alternative solution for long-term, deploy and forget, WSN. In this context, thermoelectricity is a method of choice considering the implementation context. In this paper, we present hands-on experience related to on-going implementations of thermoelectric generators (TEG) in airliners. In a first part, we will explain the reasons justifying the choice of ambient energy capture to power WSN in an aircraft. Then, we will derive the general requirements applying to the functional use of TEG. Finally, in the last section, we will illustrate the above issues through practical implementations.     

Microstructural investigations in Cf–SiC composites in as-sintered state and after creep experiments

The high interest in ceramic matrix composites during the last decade has led to a considerable number of studies devoted to their thermomechanical properties and damage processes. Despite their sensitivity to oxygen partial pressure, carbon fibres appear to possess higher stability and better mechanical properties if they are treated under protective atmospheres than other ceramic fibres (especially classical silicon carbide fibres). The aim of this investigation is to characterize at the nanoscale the main microstructural parameters of C_f–SiC composites provided by the SEP (Division of SNECMA, Bordeaux, France). This material was fabricated from a 2.5D preform made of high strength polyacrylonitrile (PAN)-based carbon fibres densified according to the chemical vapour infiltration process. A pyrocarbon (PyC) interphase was deposited on the fibre prior to the β-SiC matrix infiltration. A careful high resolution electron microscopy (HREM) microstructural investigation focused on the fibre microstructure as well as on the different interfaces in the material: pyrocarbon/fibre and matrix/pyrocarbon interfaces. All these observations have been realized in longitudinal and transverse sections of the specimen. These observations are found in good agreement with Guigon's model for high strength ex-PAN carbon fibres. The PyC interphase texture was strongly anisotropic at the fibre/interphase and interphase/matrix interfaces over a mean thickness of 8–15 nm. Tensile creep tests were performed under partial pressure of argon between 1273 and 1673 K for stress levels ranging from 110 to 220 MPa. Scanning electron microscopy and high resolution electron microscopy were used to study the microstructural modifications inside the fibres and at the different interfaces. A discussion of the possible creep mechanisms based on the microstructural investigation and the creep results is presented.     

Power Supply for a Wireless Sensor Network： Airliner Flight Test Case Study

In this paper, we present hands-on experience related to on-going implementation in aircraft of power supply for a wireless sensor network deployed for aerodynamic flight tests. This autonomous battery-free power supply is capturing, managing and storing primary energy from the environment, using solar light and PV （photovoltaic） cells. For practical purposes, it is also equipped with an auxiliary power input. The specifications are detailed, the general architecture is presented and justified, and test results are discussed.     

Multiscale investigation of the creep behaviour of a 2.5D Cf-SiC composition

This paper deals with some results on the creep behaviour of a 2.5D C_f-SiC composite. This material fabricated by CVI was tested in tension under an argon partial pressure for temperatures ranging from 1273 to 1673 K and stresses between 110 and 220 MPa. Results regarding creep curves (strain-time) and strain rate-time curves tend to confirm the existence of a secondary stage. Damage-stress and damage-time curves are also presented. The limits of the Dorns formalism are evidenced as well as the occurrence of a damage process leading to a so-called damage-creep mechanism. In order to explain this macroscopic creep behaviour of the composite, investigations at the mesoscopic, microscopic and nanoscopic scales were necessary. Five modes of matrix microcracking are observed together with different pull-out features regarding the extracted fibre surface. The damage accumulation via matrix microcracking appears to be a time dependent mechanism. Two modes of interfacial sliding are evidenced: at 1473 K and 220 MPa, the pyrocarbon (PyC) interphase is fractured leading to debonding between carbon layers, while at 1673 K, there is a loss of anisotropy of the PyC layer close to the matrix and, thus, an interfacial sliding appearing as a viscous flow. To elucidate the role of the carbon fibres, a nanoscale study via HREM has been conducted. An increase of the mean diameters of the basic structural units (BSUs) and of the areas of local molecular orientation (LMOs) within the fibres has been observed when increasing temperature under 220 MPa. In fact, these changes do not contribute to the macroscopic strain. Therefore, this restructuration effect has been called nanocreep of the carbon fibre as it appears to have a negligible contribution to the macroscopic creep behaviour of the 2.5D C_f-SiC composite.