RADIATION EFFECTS ON POROUS SILICON

Electron spin resonance (ESR) was used to study paramagnetic defects i n porous silicon. Two defects have been observed: (a) the P-bo center which exists at the interface between the pore walls and an oxidized l ayer (with the same asymmetry characteristic of similar defects found at the Si/SiO2 interface), and (b) dangling bonds with a symmetric lin eshape, which suggests the presence of an amorphous layer. Irradiation of porous silicon with gamma-rays enhanced slightly the concentration of P-bo centers but it did not introduce significant amount of E' cen ters as expected. This is explained with the strong interaction of E' centers with hydrogen present in material.