Two-color optical technique for characterization of x-ray radiation-enhanced electron transport in $SiO2$

Damage enhanced electron transport, across thin oxides in x-ray irradiated $Si/SiO2$ samples, was measured via a contactless two-color laser technique. This method involves two steps: (1) optically stimulated electron injection into the oxide and (2) detection of transport, trapping, and recombination rates using time-dependent electric-field-induced second-harmonic generation arising from charge separation at the interface. Measured electron transport rates across an irradiated oxide are found to be substantially higher in comparison to unirradiated oxides. This effect is attributed to the presence of x-ray irradiation-induced defects that act as intermediate trapping sites facilitating enhanced electron tunneling through the oxide. The possible nature of the radiation-induced trapping sites is discussed.