Laurent Mazenq

Silicon-based micromembranes with piezoelectric actuation and piezoresistive detection for sensing purposes in liquid media

In this paper, the authors report for the first time the physical cointegration of piezoelectric actuation and piezoresistive detection on resonating micromembranes dedicated to microgravimetric biosensing applications. The micromembranes are oscillated by a reverse piezoelectric phenomenon provided by a PbZrxTi1−xO3 46/54 thin layer. The oscillation amplitudes are read-out by measuring the resistance change of piezoresistors precisely located on the clamped edges of each micromembrane. The detection of the micromembranes resonant frequencies is reported in air and deionized water. A dedicated electronic set-up operating the micromembranes in a closed-loop configuration is described. The set-up enables multiplexed tracking of four micromembranes resonant frequencies in liquid media while enhancing the corresponding quality factors values. Increases up to 11-fold of the micromembranes quality factors in liquid is reported for the (0,1) vibration mode. A quality factor of up to 417 is reported in fluid.

Design of bandpass filter in W-band on a silicon membrane

The choice of membrane technology for filters in W-band was made considering the low dielectric losses observed in previous studies. Within this frequency range, the constraints related to losses and technological feasibility limit heavily the range of achievable impedances. Thus, this limits achievable bandwidth for broadband filters. Moreover for narrowband coupled-lines filters, we were faced with transmission lines shape-factor problems (wider than long). Therefore, we have chosen a narrowband pseudo-elliptic filter topology which has shown its efficiency and promising performances.

Fabrication and characterization of 100-nm wide silicon nanocantilevers using top-down approach

We present fabrication and characterization of silicon nanocantilevers as nano electromechanical systems (NEMS). We fabricated silicon nanocantilever using silicon on insulator (SOI) wafer by employing stepper UV lithography, which permits resolution of 100 nm. The nanocantilevers were driven by electrostatic force with approaching tungsten tip inside a scanning electron microscope (SEM). Both lateral and vertical resonance frequencies were visually detected with the SEM and compared with analytical results.

High-K thin films for simultaneous dielectric actuation and detection of M/NEMS flexural vibration

We show for the first time that a nanometer-scale dielectric thin film can be used as an efficient electromechanical transducer to simultaneously actuate and detect the flexural vibration of micro/nanoresonators. In this study, the first flexural vibrating mode of 16 μm long, and 350 nm-thick cantilevers are actuated by a 15 nm-thick silicon nitride layer, and detected close to resonance, at megahertz frequencies. We also measure optically its displacement, and extract and compare the transducer efficiency to an analytical model. This work would be further strengthened by the use of high-K dielectric materials obtained by atomic layer deposition.

Design, realization and characterization of all-arround SiO2/Al 2 O 3 gate, suspended silicon nanowire chemical field effect transistors

We present a sensor platform associated to silicon-nanowire chemical field effect transistors (Si-nw-ChemFET). Innovations concern the use of networks of suspended silicon N+/P/N+ nanowires as conducting channel, the realization by thermal oxidation and Atomic-Layer Deposition (ALD) of a SiO2/Al2O3 gate insulator all-around the silicon nanowires, and their final integration into covered SU8-based microfluidic channels. The Si-nw-MOSFET/ChemFET fabrication process and electrical/electrochemical characterizations are presented. The fabrication process did not need an expensive and time-consuming e-beam lithography, but only fast and low cost standard photolithography protocols. Such microdevice will provide new opportunities for biochemical analysis at the micro/nanoscale.

Spin crossover materials for MEMS actuation: Film integration and characterization

This work describes the integration of molecular spin crossover (SCO) compound [Fe(H<inf>2</inf>B(pz)<inf>2</inf>)<inf>2</inf>(phen)] 1 (H2B(pz)<inf>2</inf> = dihydrobis(pyrazolyl)borate, phen = 1,10-phenantroline) into silicon MEMS with the aim to determine the mechanical properties of the SCO thin film. Analytical methods using the experimental resonance frequency before and after deposition of 1 are used to extract the elastic modulus (E) and residual stress (σ) induced by the film deposition, leading to values of E = 6.9 ± 0.1 GPa and σ = 74.8 MPa respectively. Additional mechanical parameters as a consequence of the expected spin transition were also predicted. These results provide a step towards the integration of SCO materials for future applications as actuators in MEMS/NEMS devices.