Energy Analysis of H~(3+)Ion Beam Emitted fromGas field ionization source

摘要

Techniques for focusing ion beams are very important today in terms of industry and academia. Basically,they areoften used for sampleprocessing(for example, TEM lamella)as wellasfor observationofsample surface.For both applications, it is very important how finely the beamcan be focused.The energy dispersion of the ion beam is an important parameter which determineshow finely the beam can be focused.Agas field ionization ion source has the energy dispersion smaller than other ion sources such as a liquid metal ion sourceanditsbrightness is also as high as the field emission electron source.Our group has studied hydrogen gas field ion source.Three types of hydrogen ions, i.e., H~+, H_2~+and H)3~+can be released from the hydrogen gas field ionization ion source.It is known that H3+has smaller energy dispersion than other hydrogen ions and unfortunatelyH_3~+has been considered to be less suitable for practical usebecause of its smaller emissionamount than other ions. However, we have reported that when the emitter tipis sharpened to the atomic level,H3+gives the largestemissionamountamong the threeions with very narrow extraction voltage range. In this condition the probecurrentfor a practical use can be achieved.