Ion implantation
One of the first beam lines constructed at the new accelerator was the high energy implantation line. The line itself was designed and completed in our laboratory, using key components from several different vendors. The scanning system and the neutral ion beam trap was supplied by the National Electrostatics Corporation (NEC) USA, The implantation chamber was bought from HVEE and the vacuum beam line components and pumping system was supplied by the Vacuum Praha and Pfeiffer companies. The implantation control and operating code is based on LabWIEW and was developed by ourselves.
The sample chamber is equipped with the sample carrousel for 12 samples of 2,5 inch in diameter. Additionally we equipped the sample chamber with the step motor control of the carrousel movement, so an automated implantation of more samples is now available. The maximum energy is 2.5MeV per charge state. For Si4+ it is 10MeV, for H+ 2.5MeV. The lowest available energy is limited by the parameters of the accelerator (stable high voltage generation and stripping conditions) and it is about 300keV.
The typical implanted doses range from 1x109 to 1x1016 ions/cm2. The minimum doses are limited by the dose control, which is based on the charge measurement. The high doses are limited by the parameters of the Tandetron ion source, reasonable time of the implantation and by the sample stability. The implanted dose can be further increased by scanning over smaller area. However only time control of the implanted dose can be used in this case. There is also a demand for the implantation of very low doses. For this purpose we are now developing special system based on a very narrow slit and single scan shot. We expected to be able implant defined doses down to 1x103 ions/cm2.
Fig: RBS profil of glass implanted by Au ions with a fluence of a 1x1015 ions/cm2.