Post-buckling dynamic behavior of self-assembled 3D microstructures

The paper presents the snap-through phenomenon in the case of micro fabricated clamped-clamped buckled beam. This dynamic post-buckling behavior is likely to occur in 3D microstructures when they are subjected to large vibration amplitudes. The main difference between this work and previous studies is the MEMS specific beam dimension, especially the large initial deflection of the buckled beam that involves the inversion of the two first resonance frequencies. The mathematical development allows showing how the vibration amplitude of the supporting base affects the post-buckling dynamic behavior of the beam. For each frequency, the limit between the stable behavior and the snap-through behavior is evaluated. Moreover, the effect of environment is taken into account from the damping point of view. Samples are fabricated and the experiment is described. Measurements are compared to the theoretical approach and the results are in good agreement with the proposed model.     

Sputtered Titanium Carbide Thick Film for High Areal Energy on Chip Carbon‐Based Micro‐Supercapacitors

The areal energy density of on‐chip micro‐supercapacitors should be improved in order to obtain autonomous smart miniaturized sensors. To reach this goal, high surface capacitance electrode (>100 mF cm^?2) has to be produced while keeping low the footprint area. For carbide‐derived carbon (CDC) micro‐supercapacitors, the properties of the metal carbide precursor have to be fine‐tuned to fabricate thick electrodes. The ad‐atoms diffusion process and atomic peening effect occurring during the titanium carbide sputtering process are shown to be the key parameters to produce low stress, highly conductive, and thick TiC films. The sputtered TiC at 10^?3 mbar exhibits a high stress level, limiting the thickness of the TiC‐CDC electrode to 1.5 µm with an areal capacitance that is less than 55 mF cm^?2 in aqueous electrolyte. The pressure increase up to 10^?2 mbar induces a clear reduction of the stress level while the layer thickness increases without any degradation of the TiC electronic conductivity. The volumetric capacitance of the TiC‐CDC electrodes is equal to 350 F cm^?3 regardless of the level of pressure. High values of areal capacitance (>100 mF cm^?2) are achieved, whereas the TiC layer is relatively thick, which paves the way toward high‐performance micro‐supercapacitors.     

Modeling and experimental validation of sharpening mechanism based on thermal oxidation for fabrication of ultra-sharp silicon nanotips

This paper aims at modeling the thermal oxidation of silicon pillars leading to the formation of very sharp silicon tips. The model is used to determine optimum process parameters with respect to the initial shape of the silicon pillars and the geometry of the desired tip. The modeling concept is to extend a previous approach, which predicts the oxidation mechanism of silicon cylinders versus their initial radius. The silicon pillar geometry is approximated by a superposition of silicon cylindrical structures featuring a local curvature radius. Experimental validation has been performed for several initial silicon pillar shapes, at 1000/spl deg/C and 1100/spl deg/C under dry oxidation conditions, leading to formation of very sharp silicon tips. The numerical predictions are shown to agree well with these experimental data. The motivation of this study aims at designing and fabricating a nanoelectromechanical filter device. Its vibrating part consists of a silicon nanotip, covered with a thin gold layer, the geometrical features of which affect the center frequency of the nanofilter device.     

Size and shape effects on creep and diffusion at the nanoscale

In this paper, we have investigated the size and shape effects on creep and diffusion phenomena at the nanoscale. From a classical thermodynamic model, the higher diffusion of nanostructures is explained. As creep is particularly due to diffusion processes, it is therefore important to consider it at the nanoscale. Therefore, to be able to control creep in the nanoworld, temperature and stress thresholds, taking into account the size and shape of the nanostructure, are defined.     

Fabrication of 24-MHz-Disk Resonators With Silicon Passive Integration Technology

A new approach for the fabrication of large contour-mode single-crystal silicon resonators has been demonstrated without the use of SOI substrates. Twenty-four-megahertz disk resonators have been built thanks to industrial facilities dedicated to the integration of passive components on silicon and exhibit a good compromise between the quality factor higher than 50 000 and the motional resistance of a few kiloohms.     

Gallium nitride MEMS resonators: how residual stress impacts design and performances

Microsystem Technologies - Starting from Gallium Nitride epitaxially grown on silicon, pre-stressed micro-resonators with integrated piezoelectric transducers have been designed, fabricated, and...     

Complete System for Wireless Powering and Remote Control of Electrostatic Actuators by Inductive Coupling

This paper proposes a successful asynchronous remote powering and control of electrostatic microactuators, organized in two distributed micro motion systems (DMMS) with the aim of realizing a wireless microrobot. Remote powering of the integrated circuit (IC) and the microelectromechanical systems (MEMS) components is obtained by inductive coupling at 13.56 MHz, and the digital transmission is created by modulating the carrier amplitude by 25%. The system includes a high-voltage controller IC. It provides a link between the power and data on the receiver antenna on one side, and the actuators of the microrobot on the other. The micromachined antenna is designed to optimize the inductive coupling. The main IC building blocks, such as the received signal rectifier/amplifier, the integrated digital processing and the DMMS actuation voltage generation are given in detail. The demonstrator has successfully achieved the remote control and asynchronous operation under 100 V of two arrays of 1700 electrostatic actuators, having a capacity of 2 nF each     

Drying of Lemon Myrtle (Backhousia citriodora) Leaves: Retention of Volatiles and Color

Lemon myrtle plant (Backhousia citriodora) leaves were dried at three different drying temperature conditions (30, 40, and 50°C) in a fluidized bed dryer. The retention of the principal volatile compound, citral, was analyzed in dried products obtained at these three drying conditions. The changes in the color parameters L?, a?, b? of leaves were also analyzed. More than 90% of citral was retained at 50°C drying temperature, whereas the retention at 30 and 40°C was 81 and 85%, respectively, suggesting that higher temperature is beneficial to achieve higher retention of volatiles. However, in terms of the color, all the color parameters were changed maximum at 50°C drying temperature unfavorably, suggesting that the higher temperature drying causes more degradation of the pigment. Blanching of the leaves in hot water at 80°C for 1 min prior to drying did not result in any improvement in volatile retention or color.     

Optimization of SiNX:H films deposited by PECVD for reliability of electronic, microsystems and optical applications

This paper presents the correlation between the optical properties and the chemical and electrical properties of amorphous silicon nitride (SiN_X:H) films prepared by reactor Plasma-Enhanced Chemical Vapor Deposition (PECVD). The effects of temperature and mixture of gases (NH₃/SiH₄/N₂) on these dielectric films are investigated in this study. Silane (SiH₄) and ammonia (NH₃) are used as the reactive species, while nitrogen (N₂) is used as a dilution gas. A particular focus is made on the improvement of the electrical properties that are strongly correlated to the physicochemical bonds films properties. The incorporation of the N₂ dilution leads to the deposition rate and hydrogen content reductions in the film. An optimal gases mixture with N₂ is obtained to improve the breakdown voltage at low temperature, 200 °C. Fundamental properties of these fabricated films are characterized by their elemental composition, chemical specification, residual stress, optical and electrical properties. The results experimentally show that this film can be used to improve some of the key deposition parameters for the reliability of semiconductor, microsystems and optical applications.