Field evaporation behavior during irradiation with picosecond laser pulses

A field-ion specimen made of a low thermal diffusivity material, field evaporated using picosecond laser pulses incident from one side, is shown to develop different curvatures between the incident side and the “shadow” side of the specimen apex. Differences of approximately 2.6 and $1.5\mathrm{V}∕\mathrm{nm}$ in evaporation field were observed between the two regions of a type 304 stainless steel tip evaporated at $50\mathrm{K}$ with pulsed laser intensities of 0.04 and $0.02\mathrm{nJ}∕\mu {\mathrm{m}}^2\mathrm{ps}$ , respectively. This indicates that diffraction of the laser beam cannot ensure uniform illumination and heating over the tip apex.