Emission characteristics of Au_(60)Be_(40) and Au_(62)Si_(23)Be_(15) liquid metal ion sources

摘要

The angular current densities, relative abundance, and total energy distributions (TEDs) of the various ion species from the binary Au_(60)Be_(40) and ternary Au_(62)Si_(23)Be_(15) liquid metal ion sources (LMISs) have been measured. The results support a postionization mechanism for the formation of the various monoatomic M~(+2) species, while the M~+ species are formed by a combination of field evaporation, field ionization, and charge exchange mechanisms. All ion species show an increase in the full width at half maximum of the TEDs with total emission current, mass, and charge. The dominant monoatomic species at 5 μA total emission current are Au~+ (64%), Au~(+2) (15%), Be~(+2) (10%), and Be~+ (3.2%) for the binary LMIS and Au~+ (63%), Au~(+2) (13%), Si~(+2) (3.2%), Be~(+2) (2.1%), and Be~+ (0.71%) for the ternary LMIS. The predicted beam sizes for Au~(+2) and Be~(+2) for the binary LMIS at a beam current of 5 pA in a typical focusing column are 15 and 8 nm, respectively.