Electron trapping in amorphous SiO2 studied by charge buildup under electron bombardment

Electron bombardment of thick pure SiO2 induces the buildup of a negative charge which can be observed through a ‘‘mirror’’ effect in a conventional Auger scanning microscope. A mechanism for the creation of this charge is proposed in terms of trapping of an electron in defects due to the irradiating beam. The influence of temperature is studied on amorphous and monocrystalline SiO2. The temperature dependence of the existence of high negative charge shows around 270 °C an anomalous effect which depends on the irradiation time. The role of electronic excitation to produce defects in silica is discussed.