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| CHEMO-OPTICAL SENSORS |
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MOEMS FOR AIR POLLUTION MONITORING |
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The main output (photocurrent) of the software simulator for silicon photodiodes |
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Chemo-Optical Silicon Sensor |
| There are two type of sensors: absorptive (Fig. 1) and refractive (Fig. 2) ones. There are two branches: a measurement one and a reference one, coupled with an Y branch. On the measurement waveguide a chemical layer is deposited in the sol-gel technique, working as the transducer. The real part (refractive sensor) respectively the imaginary part (absorptive sensor) of the refractive index of the chemical layer is dependent on the external substance concentration. The output radiation on each branch is measured by the photodiodes, which generate a convertible output current. |
| Fig.1 Integrated chemo-optical absorptive sensor structure: |
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| Fig. 2 Integrated chemo-optical refractive sensor: |
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The sensitive layer is a silicon dioxide obtained by sol-gel technology. Their chemo-optical properties are enhanced for λ=904 nm
The optical wave-guide core is made by silicon oxinitride in the CVD technique |
| Refractive index |
1.67 |
| Thickness |
0.5 μm |
| Width |
15 μm |
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The buffer and cover of the wave-guide are made by silicon dioxide in the CVD technique.
The P+N photodiodes are realised in the planar technology |
| Responsivity at λ = 904 nm |
0.45 A/W |
| Junction depth |
3 μm |
| Length |
100 μm |
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