The construction of an atom probe field ion microscope, which is a combination of probe hole field ion microscope and time flight mass spectrometer having single ion sensitivity, are described.
The characteristics of the high voltage naosecond pulser, single ion detector and the specimen tip manipulator are examined and are discussed. The details of the transmission line of nanosecond pulse and the vacuum system are also described.
The M/n ratios are computed from the equation
M/n=0.272 (V0+αVp) (t-δ) 2
for this system. The pulse factor α and delay time δ are determined from two different methods : (1) the differences between the travel times of Rh2+ and Rh+, (2) the Newton-Raphson method, which is determined numerically in minimizing the difference between M/n ratio of 51.5 and the value estimated from the experiments for Rh2+. The numerical values of α=0.751 andδ=0.290 (μs) were determined using single isotope rhodium tips. The consistene values of M/n were also obtained for W, Ta, Nb, Ir, Mo and Pt using above results. The mass resolution of the spectrometer have been discussed.
