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Placidi M.,IMB CNM | Perez-Tomas A.,IMB CNM | Zielinski M.,NOVASiC | Godignon P.,IMB CNM | And 4 more authors.
Journal of Micromechanics and Microengineering | Year: 2010

Here, we report on a comparison between two different insulated substrates, semi-insulated silicon (SIS) and silicon-on-insulator (SOI), used for the growth of 3C-SiC for electrostatic-based mechanical resonators able to operate at high temperatures. The epitaxial growth of monocrystalline 3C-SiC films in these starting materials is first described and the main encountered problems are discussed. Structural and morphological characterization of the SiC layers is then performed using an optical microscope, a scanning electron microscope, an atomic force microscope and x-ray diffraction. Raman spectroscopy is also used to study the residual stress. Then, innovative lateral electrostatic SiC resonators using these materials are fabricated and electrically tested. Globally, devices using a SOI substrate allowed electrical sensing without any associated circuitry. Temperature measurements of the electrical resonance up to 200 °C are also performed and demonstrate that SiC on SOI is a promising material for a new generation of a harsh-environment-resistant micro-electro-mechanical system. © 2010 IOP Publishing Ltd.

Wahab H.F.,University of Strathclyde | Katebi R.,University of Strathclyde | Villanova R.,ETSE
2012 20th Mediterranean Conference on Control and Automation, MED 2012 - Conference Proceedings | Year: 2012

This paper deals with five existing nonlinear estimators (filters), which include Extended Kalman Filter (EKF), Extended H-infinity Filter (EHF), State Dependent Filter (SDF), State Dependent H-Infinity Filter (SDHF) and Unscented Kalman Filter (UKF) that are formulated and implemented to estimate unmeasured states of a typical biological wastewater system. The performance of these five estimators of different complexities, behaviour and advantages are demonstrated and compared via nonlinear simulations. This study shows promising application of UKF for monitoring and control of the process variables, which are not directly measurable. © 2012 IEEE.

Placidi M.,IMB CNM | Perez-Tomas A.,IMB CNM | Godignon P.,IMB CNM | Mestres N.,ICMAB | And 3 more authors.
Materials Science Forum | Year: 2010

In this study, a SiC on insulator growth is optimized, in order to electrically isolate the active structural layer towards the substrate. High quality single crystalline SiC was grown on SOI and SIS substrates. Smooth surface, low stress and bowing, confirmed by microscopy techniques, SEM, AFM, X-Ray diffraction and Raman spectroscopy, have been obtained. SiC electrostatic resonators on insulated substrates were also fabricated, and electrically driven. These results demonstrate that this material is very promising for MEMS application requiring isolation from the substrate and operation in harsh ambient. © (2010) Trans Tech Publications, Switzerland.

Perez-Tomas A.,Catalan Institute of Nanoscience and Nanotechnology | Catalan G.,Catalan Institute of Nanoscience and Nanotechnology | Catalan G.,Catalan Institution for Research and Advanced Studies | Fontsere A.,ALBA Synchrotron | And 13 more authors.
Nanotechnology | Year: 2015

The gallium nitride (GaN)-based buffer/barrier mode of growth and morphology, the transistor electrical response (25-310 C) and the nanoscale pattern of a homoepitaxial AlGaN/GaN high electron mobility transistor (HEMT) have been investigated at the micro and nanoscale. The low channel sheet resistance and the enhanced heat dissipation allow a highly conductive HEMT transistor (Ids>1 A mm-1) to be defined (0.5 A mm-1 at 300 C). The vertical breakdown voltage has been determined to be ∼850 V with the vertical drain-bulk (or gate-bulk) current following the hopping mechanism, with an activation energy of 350 meV. The conductive atomic force microscopy nanoscale current pattern does not unequivocally follow the molecular beam epitaxy AlGaN/GaN morphology but it suggests that the FS-GaN substrate presents a series of preferential conductive spots (conductive patches). Both the estimated patches density and the apparent random distribution appear to correlate with the edge-pit dislocations observed via cathodoluminescence. The sub-surface edge-pit dislocations originating in the FS-GaN substrate result in barrier height inhomogeneity within the HEMT Schottky gate producing a subthreshold current. © 2015 IOP Publishing Ltd.

Fontsere A.,IMB CNM CSIC | Perez-Toms A.,IMB CNM CSIC | Placidi M.,IMB CNM CSIC | Llobet J.,IMB CNM CSIC | And 10 more authors.
Applied Physics Letters | Year: 2011

As GaN technology continues to gain popularity, it is necessary to control the ohmic contact properties and to improve device consistency across the whole wafer. In this paper, we use a range of submicron characterization tools to understand the conduction mechanisms through the AlGaN/GaN ohmic contact. Our results suggest that there is a direct path for electron flow between the two dimensional electron gas and the contact pad. The estimated area of these highly conductive pillars is around 5 of the total contact area. © 2011 American Institute of Physics.

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