N-type in-situ doping effect on vapour liquid solid silicon nanowires properties for gas sensing applications
Résumé
N-type in-situ doped SiNWs based resistors are fabricated and used as gas (ammonia) sensors. SiNWs are prepared by Vapour Liquid Solid method (VLS) using gold as catalyst. In-situ doping level is adjusted by varying the phosphine to silane mole ratio. Because SiNWs can act as sensitive units specific design is de-veloped to allow large sensing areas, following a process fabrica-tion compatible with a mass production planar layout. SiNWs doping effect on ammonia detection is carried out under controlled ammonia/nitrogen mixture varying from 2 ppm to 700 ppm. Results highlight that the relative response, Sg=(I0-Ig)/I0, where I0 and Ig are the current values in vacuum and reactive ambient re-spectively, follows a linear behaviour. The relative sensitivity, (S=deltaSg/delta[NH3]) decreases, whereas the sensitivity (SxI0) in-creases with the increase of the VLS SiNWs doping level