Direct measurement of transient electric fields induced by ultrafast pulsed laser irradiation of silicon

We use 30 kV electron pulses to probe transient electric fields above silicon surfaces by pump-probe. Electron beam deflection at 0.29 mm away from the sample surface on the order of 10-2 degrees is measured as a function of time delay and used to measure the local electric fields. The measured field strength and direction change with time; at the pump laser fluence of 67.7 mJ/ cm2, the maximum field reaches 34 kV/m. We model the transient electric fields based on the propagation of electrons emitted from the Si surface and the percentage of electrons escaping from the surface.