Study of the interaction mechanisms between absorbed NO$_2$ and por-Si/SnO$_x$ nanocomposite layers

The interaction mechanisms between NO$_2$ molecules and the surface of por-Si/SnO$_x$ nanocomposites obtained by magnetron deposition and chemical vapor deposition (CVD) are studied by infrared absorption spectroscopy and electron paramagnetic resonance methods. The observed increase in the free carrier concentration in the por-Si/SnO$_x$ nanocomposite layers is explained by a change in the charge state of $P_b$ centers due to the formation of neutral "surface defect-adsorbed NO$_2$ molecule" complexes with free carrier generation in the crystallite bulk. In the nanocomposite layers grown by the CVD method, the increase in the free hole concentration during NO$_2$ adsorption is much less pronounced in comparison with the composite grown by magnetron deposition, which is caused by the competing interaction channel of NO$_2$ molecules with electrically neutral $P_b$ centers.