Charge emission in thermal poling of glasses with carbon film anode

Electric fields ∼109 V/m can be induced in glass platelets at a temperature of ∼300°C and some kilovolts applied across its thickness. This glass poling process finds applications in non-linear optics. The electric field is confined to an alkali-ion depleted region formed near the anode side of the sample. Partial neutralization mechanisms are assumed to take place during poling, one possibility being the emission of negative charges from the depletion region. To investigate this emission, soda lime glass platelets were poled at 270°C in vacuum up to 2.5 kV. A thin (∼20 nm), amorphous carbon film was sputtered on one surface of each sample and used as anode allowing eventual charges emitted to be collected in a Faraday cup. Emission occurred in pulses with ∼200 μs duration consisting of ∼108 elementary charges of ⩽60 eV energy. The pulse occurrence probability was inversely proportional to its charge. Charge emission was not detected with aluminum film anodes. The pulse generation process is still under inspection.