Akinori Mogami

Resolution of time‐of‐flight mass spectrometers evaluated for secondary neutral mass spectrometry

Mass resolution of a time‐of‐flight mass spectrometer with a two‐stage electrostatic reflector is calculated for secondary neutral mass spectrometry. The instrument parameters are optimized for energy and space focusing: correcting the flight time difference due to the energy width ΔE of sputtered particles and the spatial width Δs of an ionizing laser beam. The effect of Δs can be compensated by applying an acceleration field to the ionizing region, and the maximum resolution becomes about 1000 for ΔE=10 eV and Δs=1.0 mm.

Optical properties of immersion objective lenses and collimation of secondary electrons in low-voltage SEM

Optical properties of two kinds of immersion lenses, i.e. the radial gap magnetic lens and the combined electric and magnetic field lens have been compared. When the specimen allows the application of a leakage electric field about 600 V and the accelerating voltage on the specimen is lower than 2 kV, the combined field lens is better than the radial gap lens, because the spherical and chromatic aberration coefficients are small and the collimation efficiency of secondary electrons is perfect. However, if the leakage electric field is not allowed, the radial gap lens is superior to the combined field lens. In the case of the radial gap lens, a weak electric field has to be applied to the specimen for collimating electrons emitted with large angle from the specimen. When the specimen is set lower than the magnetic field maximum position, a solenoid coil placed inside the yoke of the lens is useful to bring up the off axial electrons.

Development of a double-focusing mass analyzer with crossed field using a multielectrode.

A double-focusing mass analyzer (γ=150 mm) with crossed electric and magnetic field is developed. A newly designed multielectrode is used to make the electric field in the narrow gap between the magnet pole pieces. Experimental results verify the following features of this mass analyzer as predicted theoretically; 1) much wider energy window of approximately 1 keV, 2) mass spectrum available by voltage scanning as well, 3) high mass resolution of 1,700 obtained with the wide main slit of 0.1 mm.