Table 3: Ion sources (list of LMIS sources from [7, 20, 22, 163]). The ion species listed as “available” are available from well-developed sources and are featured in commercial instruments.

Source typeGeneral propertiesIon species

Liquid metal ion sourcesVirtual source size 10–20 nm
Typical pattern res 10–20 nm
Typical beam currents up to a few nA for Ga and up to 10–100 pA for most other species 
Very good long-term stability and lifetime for Ga, improving performance for well-known systems like AuSi and AuGe
Sputter yield mostly medium to large
Available: Ga, Au, Si, Ge 
Also exist: Ag, Al, As, B, Be, Bi, C, Ce, Co, Cr, Cs, Cu, Dy, Er, Fe, Hg, In, K, Li, Mg, Mn, Na, Nb, Nd, Ni, P, Pb, Pd, Pr, Pt, Rb, Sb, Sm, Sn, U, Y, Zn

Gas field-ionization sourcesVirtual source size below 2 nm (He, Ne)
Typical pattern res 5–10 nm
Typical beam currents up to 10 pA
Limited stability and lifetime
Sputter yield mostly small to medium
Available: He, Ne 
Also exist: H, Ar

Plasma sourcesVirtual source size ~10 µm 
Typical pattern res 100 nm–1 µm 
Typical beam currents up to a few µA 
Good stability 
Sputter yield mostly medium to large
Available: Ar, Xe 
Also exist: H, He, N, O