Porträt Dr. Bischoff, Lothar; FWIZ-N

Dr. Lothar Bischoff
Ion Induced Nanostructures
Phone: +49 351 260 2866, +49 351 260 2963
Fax: +49 351 260 12866

LMAIS development and testing


Liquid Metal Ion Sources (LMIS) are ion sources with a very high brightness and a point like emission area, which make them very suitable for use in focused ion beam application.  There are needle and capillary type LMIS. The application of a strong electric field in front of the emitter tip leads to the formation of a so called Taylorcone from which the ion emission occurs. This process is called field evaporation. As source material pure metals (Ga, In, ... - LMIS) or eutectic alloys (AuSi, CoNd, MnGe, ... - LMAIS) can be used .

Required properties of these materials:

  • high concentration of the wanted component in the alloy
  • low melting point
  • low vapour pressure at that temperature
  • good wetting behaviour to the needle
  • no chemical reactions or phase transitions with the emitter


The FIB laboratory of the Institute has the experience and the equipment for the development, fabrication and analysis of new needle type alloy LMIS, which are summarized in the Table:
Material Melting Point (°C) Applications
Au73Ge27 365 Au:Sputtering, nanocluster; Ge: Doping, SixGe1-x alloy
Au77Ge14Si9 365 Si:contamination free processing, imaging
Au82Si18 365 dto.
Co36Nd64 566 Co:CoSi2 ; IBS, Nd: optical + magnetic application
Co27Ge73 817 Co:magnetic application
Er69Ni31 765 Er:optical application
Er70Fe22Ni5Cr3 862 Fe,Ni,Cr:  magnetic application
Sn74Pb26 183 Sn:doping, academic
In14Ga86 14.2 Academic, source emission investigation
Mn45Ge55 720 Mn implantation in compound semiconductors
Ga38Bi62 222 Ga: acceptor; Bi: shallow donor in Si
Ga35Bi60Li5 250 Li: source for analysis and ion beam lithography
Ga 29.7 All classical FIB applications
Bi 271.5 Surface modification by monomers and clusters


For testing and characterisation of new LMAIS emitters, the following ion source parameters can be measured:

  • Current - Voltage - characteristics, stability of emission, life time and temperature behaviour
  • Mass spectra (below shown for GaBi LMAIS)
  • Distribution and angular intensity by means of a rotating Faraday cup
Masse spectra of a GaBi LMAIS as a function of the ion emission current
(click to enlarge)
Ion energy distribution and energy deficit of each emitting component of the source using a mass filter and a retarding field analyzer
FWHM of the energy distribution of different ion species as a function of mass and charge state
(click to enlarge)
FWHM of the energy distribution for different ion species with different masses and charge states at an emission current of 15 µA.



Dr. Lothar Bischoff
Ion Induced Nanostructures
Phone: +49 351 260 2866, +49 351 260 2963
Fax: +49 351 260 12866