Investigation of charge state of field-ionized noble gases by time-of-flight mass spectrometry

Charge state distributions of Ar and Ne Gas Field Ion Source (GFIS) were investigated by time-of-flight mass spectrometry using a newly designed experimental system. GIFS emitter having few atoms on the top of a (111) surface of tungsten were formed by remolding and field evaporation sequence with electrochemically etched <;111>; oriented tip. At the probe current of about lpA, the ratio of standard deviation of fluctuation and average ion current <; 2.5% was recorded from a single atom terminated emitter Ar-GFIS. Mass analysis by time-of-flight spectrometer showed that there were only singly charged ions both of Ne- and Ar-GFIS. Furthermore, no impurity gas was detected in the mass spectrum. These findings look promising for the development of both Ne and Ar GFIS systems.