O. De Sagazan

Selenide sputtered films development for MIR environmental sensor

A micro-sensor based on selenide glasses for evanescent wave detection in mid-infrared spectral range was designed and fabricated. Ge-Sb-Se thin films were successfully deposited by radio-frequency magnetron sputtering. In order to characterize them spectroscopic ellipsometry, atomic force microscopy and contact angle measurements were employed to study near and middle infrared refractive index, surface roughness and the wettability, respectively. Selenide sputtered films were micro-patterned by means of reactive ion etching with inductively coupled plasma process enabling single-mode propagation at a wavelength of 7.7 µm for a waveguide width between 8 and 12 µm. Finally, optical waveguide surface was functionalized by deposition of a hydrophobic polymer, which will permit detection of organic molecules in water. Thus, the optical transducer is a ridge waveguide composed by cladding and guiding Ge-Sb-Se sputtered layers exhibiting a tailored refractive index contrast and a polymer layer onto its surface ready for environmental detections in middle infrared.

Transferrin Electronic Detector for Iron Disease Diagnostics

Field effect transistor (FET) structure with suspended bridge shows the ability to detect proteins with very high sensitivity. This sensor is tested for the transferrin, a specific blood plasma protein, relevant in iron disease diagnostic. This system is based on field effect transistor with a suspended bridge used as a gate electrode. The sensitive layer is made of silicon nitride as in the ISFET (ion sensitive field effect transistor) technology. The surface micro-technology ensures a small height suspended-bridge (0.5 mum) composed of poly-silicon insulated with silicon nitride. To improve sensitivity and to limit biofouling, proteins are selected by antibodies covalently bound to organic layers. The specific charge of the fixed transferrins translates the transistor transfer characteristics. For low concentration, resulting shift is important and confers a good sensitivity to our electronic transducer.

A heat balanced sigma–delta uncooled bolometer

This paper describes a heat balanced bolometer with an integrated CMOS sigma–delta interface. The sigma–delta interface accomplishes both the analogue-to-digital conversion and the heat feedback and therefore no other digital core is required. The heat feedback is implemented using a capacitively coupled electrical substitution technique with a digitally modulated signal that enables feedback linearization. Proof of concept is experimentally demonstrated with a polymer-type resistive bolometer and infrared optical source.

Microfabricated test structures for thermal gas sensor

Microfabricated test structures are presented for the proof validation of a new chemical sensor concept. The proposed detection principle is based on time constant shift of a thermal device covered with zeolites when target species are adsorbed.

Low Concentrated DNA Detection by SGFET

In this work a device based on oligonucleotide hybridization charged detection is presented. This biosensor is a SGFET (suspend gate field effect transistor), it is based on a MOSFET (metal oxide semiconductor field effect transistor) structure whose gate is suspended. The insulating layer (empty gap) is chemically modified by immobilized molecular receptors that enable miniaturized label free DNA detection. This method allows direct, time-resolved and in situ detection of specific nucleic acid binding. By the use of SGFET, the immobilization of DNA sequences brings negatives charges due to their phosphate groups under the gate and induce large shift of transfer characteristic. One of the applications of this device can be clinical testing.

pH sensing from frequency response of SGFET

This paper presents suspended gate field effect transistors (SGFET) used as highly sensitive pH sensors. The devices are there characterized in dynamic mode. The gain, measured versus frequency, is studied for different pH values and shows a resonance frequency depending on the pH value. These results, obtained with different geometries of SGFET, give an opportunity to develop new microsystems, CMOS compatible, highly sensitive to pH.

Electrical detection of very low content of transferrin in view of iron metabolism characterization

Suspended-gate FETs, namely SGFET, with sub-micron gap are used to detect electrically transferrin concentration directly without any labelling. The fabrication of the device and the process to functionnalize it, so that it will be able to detect transferrin, are given. The feasibility of the detection is demonstrated and a range of detectable concentrations is determined. Concentration, as low as 100 ng/mL, is measured. The maximum concentration in the linear regime, 5 mug/mL, is under the range of the standard clinical techniques. The fabrication of the device is compatible with usual microelectronic tools. Its functionalization can be easily implemented in any chemical environment. Present results open the way to simultaneous detection of many proteins giving in real time indication on complicated biologic functions as liver metabolism.

Development of suspended gate field effect transistors array-based microsystem for pH measurements

This work presents the specifications of a microsystem which allows pH electrical measurements of solution especially for water monitoring applications. The architecture of this microsystem consists in SGFET (Suspended gate Field Effect Transistor) array-based, control and processing modules. The array is composed of 3 × 3 identical SGFET sensors. Each SGFET can be addressed independently to increase the accuracy and the reliability of the global measurements.

Zeolite-based thermal mass gas sensor with self-identification algorithm

We demonstrate a new operation mode of thermal gas sensor based on thermal mass extraction with identification algorithm. The system is a silicon microstructure covered with zeolites operated at constant temperature while stimulated by heat pseudo-random sequence. The proposed detection principle is demonstrated at room temperature and atmospheric pressure through the detection of gas water molecules with an hydrophilic FAU-type zeolite coating.

1540 to 1645 nm continuous VCSEL emission based on quantum dashes

We report on an optically excited InAs quantum dash vertical cavity surface emitting lasers (VCSEL) on InP substrate. By introducing a wedge microcavity design, we obtain a spatial dependence of the resonant wavelength along the wafer, enabling us to monitor the gain material bandwidth. In this paper we show a continuously variable VCSEL emission from 1645 down to 1540 nm all across the wafer, a consequence of the important and wide gain afforded by the use of optimized quantum dashes.