Experimental observation of glassy dynamics driven by gas adsorption on porous silicon

We report on electrical resistance measurements of mesoporous silicon samples at room temperature, in the presence of various dosages of ammonia, showing very slow non-exponential responses of the system to any variation of ammonia pressure. Resistance always relaxes according to a stretched exponential law, independently of the sign of the variation. Moreover, the system remembers its own history, and memory effects can be accounted for in a very simple way in the framework of the same relaxation law. A possible extrinsic scenario based on rearrangement of trapped charges is proposed and discussed. These findings suggest that mesoporous silicon in the presence of polar molecules may be regarded as a suitable system for the study of glassy dynamics by means of electrical measurements at RT.