APSFET (Adsorption Porous Silicon FET) is a porous silicon-based device constituted of a FET structure with a porous adsorbing layer between drain and source. Adsorbed gas molecules in the porous layer induce an inverted channel in the crystalline silicon under the porous silicon itself. The mobile charge per unit area in the channel depends on the molecular concentration in the sensing layer, so that adsorbed gas plays a role similar to the charge on the gate of a FET. In this work NO(2) detection by using the APSFET is demonstrated for the first time. NO(2) concentration as low as 100 ppb was detected. Unfortunately, such high sensitivity is obtained only for fresh samples, due to a drift of sensor properties with the sample aging. A low thermal oxidation was performed on fresh samples in order to passivate the porous silicon surface. The oxidation step positively affects the sensor in term of stability of electrical performances, keeping the high response to nitrogen dioxide.
|Titolo:||Detecting NO2 with APSFET, an adsorption porous silicon FET|
|Autori interni:||BARILLARO, GIUSEPPE|
STRAMBINI, LUCANOS MARSILIO
|Anno del prodotto:||2004|
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