2024 Volume 59 Issue 2 Pages 62-66
A scanning electron microscope (SEM) equipped with a high-brightness monochromatic photocathode was constructed to visualize high-speed phenomena occurring in localized regions on a sample surface. This photocathode has high brightness comparable to that of a Schottky-type emitter, and narrower energy width than that of a cold field emission emitter. In addition, this high-brightness NEA photocathode can generate a pulsed electron beams with a minimum duration of picoseconds. Using this prototype SEM, we performed a proof-of-principle experiment of time-resolved measurement by applying pump-probe method. A sample voltage was synchronized with an excitation light source of the photocathode. A sinusoidal periodic voltage with a period of 30 ns (frequency 33 MHz) and a voltage amplitude of 0 to +5 V was applied to a sample, and SEM images were obtained by controlling a timing of a 150-picosecond pulse electron beam. A time variation of surface potential of an AlTiC sample, which exhibits characteristic image contrast in a secondary electron image, was measured as an SEM image, and it was found that both nanosecond temporal resolution and nanometer spatial resolution are possible. (171 words)
