A creation of cryogenic electron emission microscope and the applications to solid surfaces.

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A new electron emission microscope using photons, low-energy electrons, and metastable atoms as an excitation source has been developed to study spatiotemporal phenomena occurring at a solid surface. The metastable atoms such as He*(2^3S) were produced by cold-discharge and the beam intensity was attained to 〜10^16 He(2^3S) atoms s^<-1> sr^<-1>. The electrostatic and magnetic lens systems were designed at our laboratory for the low-energy electron gun and electron emission microscope based on a computer simulation program. The spatial resolution of the microscope thus constructed is 100 nm at present and will be improved by beam adjustment. We also developed a sample cooling system from some K to 1000 K to observe images of samples held at low temperature. Further we have observed PEEM images of stoichiometric NiO and chemisorbed oxygen during heating of the oxygen-exposed Ni(100), indicating that the desorption of the oxide layer proceeds inhomogeneously in space.