ENHANCEMENT OF LASER-INDUCED ELECTRON-EMISSION FROM FERROELECTRICS BY SURFACE-CHARGE REFRESHMENT

The emission from ferroelectric material is dominated by surface electrons, which screen a large part of the spontaneous polarization. The surface charge compensation of the polarization can be modified by various methods in certain limits and, hence, also the efficiency of the electron emission. An increase of the emitted charge by laser irradiation of more than two orders of magnitude was measured after switching the polarization of polycrystalline lead-lanthanum-zirconium-titanate ceramics (PLZT). An enhancement of electron emission is also observed by pre-illumination with laser light in absence of an extraction voltage compared to regular illumination under a dc extraction field. The laser-induced emission is shown to be dependent on the ferroelectric state and on the full absorption of the laser light in the material.