Propriétés électriques d'hétérostructures a-GaAs/c-GaAs(n) et de structures de type MIS a-GaAsN/c-GaAs(n)

Heterojunctions were fabricated by deposit of amorphous GaAs and GaAsN on c-GaAs. $I(V)$ and $C(V)$ measurements were performed to determine electrical properties of these structures. The a-GaAs/c-GaAs(n) heterojunctions present a p-n junction like behaviour. The characteristics of the a-GaAsN/c-GaAs(n) heterojunctions present a MIS like structure behaviour with some imperfections. A fixed positive charge was detected and a density of interface states of about $10^{11}$ eV$^{-1}$cm$^{-2}$ was evaluated.L'étude porte sur des couches minces de GaAs et de GaAsN amorphes déposées par pulvérisation cathodique RF réactive sur des substrats de GaAs cristallin. Les caractéristiques électriques $I(V)$ et $C(V)$ ont été mesurées. Les hétérojonctions a-GaAs/c-GaAs(n) présentent un effet redresseur. Cet effet laisse place à une caractéristique symétrique avec une forte atténuation de l'intensité du courant pour les structures a-GaAsN/cGaAs(n). Les structures réalisées ont alors un comportement semblable à celui d'une structure MIS imparfaite. L'existence d'une charge positive fixe dans le a-GaAsN a été mise en évidence. La densité des états d'interface au milieu de la bande interdite est évaluée à quelques $10^{11}$ cm$^{-2}$eV$^{-1}$

Low-noise micro-power chopper amplifier for MEMS gas sensor

In this paper, a low-noise, low-power and low voltage Chopper Stabilized CMOS Amplifier (CHS-A) is presented and simulated using transistor model parameters of the AMS 0.35 μm CMOS process. This CHS-A is dedicated to high resistive gas sensor detection. The proposed CHS-A using Chopper Stabilization technique (CHS) exhibits an equivalent input referred noise of only 0.194 nV/√Hz for a chopping frequency of 210 kHz under ۫.25 V supply voltage and 26.5 dB voltage gain. The inband PSRR is above 90 and the CMRK exceeds 120 dB. At the same simulation condition, the total power consumption is 5 μW only

Development of integrated smart nose based on WO3 gas sensors

International audienceThis article deals with the conception and realisation of a new architecture of integrated electronic nose based on silicon microhotplates and WO 3 thin films. The first part of this work describes technological choices to elaborate a single gas sensor with low consumption (˜100 mW to reach 600°C), low thermal inertia (˜30ms), above all with a good heater stability. By consideration of response times and relative resistance variations from sensor response curves, it is possible firstly to discriminate different gas mixtures and secondly to evaluate gas concentrations by using mathematical analysis

Structural and NH 3 gas-sensing properties of La 0.8 Ca 0.1 Pb 0.1 Fe 1-x Co x O 3 (0.00 ≤ x ≤ 0.20) perovskite compounds

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A Novel High Linear CMOS Fully Integrated PA for the Design of Zigbee Transmitters

International audienceThis paper describes a 863-870-MHz transmitter for wireless sensor applications. The fully integrated designed circuit is based on AMS0.35-mu mCMOS standard technology. The transmitter presented is composed by four stages: quadrature voltage-controlled ring oscillator (QVCO) controlled by a voltage (V-CTRL), two passive switch mixers, two combiners (a substractor and an adder), and a novel high linear power amplifier (PA). Combiners and the PA has the distinction of being based on CMOS inverter circuit. The post-layout simulation of the fully differential transmitter, at the desired oscillation frequency and under a supply voltage of 3.3 V, shows that proposed circuits satisfy specifications desired especially the output power level and PA linearity

A New Active Organic Component for Flexible Ammonia Gas Sensors

The objective of this study was to realize flexible gas sensors using low cost solution processing such as drop casting. As active sensor material, a p-type organic semiconductor, αα-ωω-hexyl-distyrylbithiophene (DH-DS2T), was used. DH-DS2T based transistors exhibit high mobility together with a good air stability. As a chemical compound, DH- DS2T presents a good solubility in common organic solvent, which means thin films could also processed by solution fabrication. Sensor responses were studied by measuring the current through the semiconductor organic film as an ammonia gas concentration function (NH3: 25, 50, and 100 ppm). We demonstrate here that DH-DS2T has efficient sensor responses and leads to an efficient fully solution processed gas sensor on flexible substrate

Correlation between structural, magnetic and gas sensor properties of L a 0.885 P b 0.005 C a 0.11 F e 1 - x C o x O 2.95 ( 0.00 ≤ x ≤ 0.15 ) compounds

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