A study on reactivity of p(+) porous silicon layers (PSL) to different gas
atmosphere has been carried out. Substrate doping was 5-15 m Omega cm and 0
.5 Omega cm, porosity ranged from 30 to 75% and the thickness of the porous
layers was 20-30 mu m. Three different processes to insure good electrical
contact are proposed and discussed. PSL were kept at constant bias and cur
rent variations due to interaction with different concentrations of NO2 wer
e monitored at constant relative humidity (R.H.). Measurements were perform
ed at room temperature (R.T.) and at atmospheric pressure. Concentrations a
s low as 1 ppm were tested, but the high sensitivity of the sensor makes po
ssible to test lower values. The recovery time of the sensor is of the orde
r of one minute. Response to interfering gases (methanol, humidity, CO, CH4
, NO, NO2) has been examined also. In-situ FTIR spectroscopy in NO2 atmosph
ere shows a fully reversible free-carrier detrapping in the IR region. conf
irming the validity of the models proposed in the recent past for electrica
l conduction in mesoporous silicon. (C) 2000 Elsevier Science S.A. All righ
ts reserved.