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摘要
Amorphous N-doped H: SiO2 films on silica prepared by Matrix Distributed Electron Cyclotron Resonance method were irradiated by electron-beam with different doses. With Maker fringe measurements, second-harmonic generation was observed in the irradiated regions and the films exhibited a maximum second-harmonic signal under the 5 mu A/cm(2), 480s irradiation condition. The magnitude of the induced second order nonlinear coefficient d(33) is of the order of 0.003 pm/V. The d33 is small but the striking feature is the observation of a surface level shift connected to electron-beam poling with topography measurements. The surface level shifts increased with the increasing of electron doses in both X and Y directions, which fact was related to the implanted electron, dose. With different temperature for an annealing time of 1/2h, the surface level shifts in both X and Y directions increases firstly and got the maximum change at 300 degrees C, and then decreases when the temperature was increased. In the same time, the second-harmonics (SH) signal decreased to zero. The surface was recovered at the temperature of 1250 degrees C, which means that there was no matter loss with electron-beam writing in the films. The second harmonic generation in the films is caused by the frozen-in electric field induced by the charge implantation from the electron-beam ( second order non linear coefficient chi((2)) is proportional to this electric field). The strength of the electric field is determined by two conditions: the trapping centers ( numbers, depth) and the remaining conductivity under large electric field.
