Laser-induced electron beam emission from titanium dioxide on silicon photocathodes treated with cesium and barium oxide

Electron beam sources are essential for a wide range of applications, including microscopy, high-energy physics, quantum science, spectroscopy, interferometry or sensors technology. However, conventional electron sources face critical limitations in energy spread, beam current, and stability. We present and characterize a laser-stimulated electron beam source based on a titanium dioxide (TiO2) surface on n-type doped silicon, coated with cesium (Cs) and barium oxide (BaO) to reduce the work function. This approach harnesses the surface photovoltage (SPV) phenomenon in an n-type semiconductor, wherein laser activation drives charge drift toward the surface, reducing band bending and further lowering the work function. The electrons are then extracted through low-voltage field emission. Experimental investigations were conducted using a low-energy electron microscope (LEEM) and a custom field emitter characterization setup. By illuminating the TiO2 sample with laser wavelengths of 830 nm, 404 nm and 824 nm, we achieved work functions below 1 eV. The results demonstrate beam currents up to 30 nA, a clearly defined two-peak energy spectrum, and an energy distribution as narrow as 100 meV in the primary peak. These findings establish SPV as a promising alternative for generating electron beams, paving the way for innovative field emitter designs and applications.