Development of ion irradiation system for in situ observation of ion irradiated semiconductor surfaces by ultra high vacuum scanning tunneling microscope

A compact ion irradiation system suitable for in situ observation of semiconductor surfaces under irradiation by low energy ions has been developed. The irradiation system contains a liquid metal ion source which provides low energy ions (100-500 eV) with the current of up to 100 pA under the pressure of less than7 × 10 ^-8Pa. The highly oriented pyrolitic graphite was irradiated by Ga ⁺ ions with energies between 100-300 eV and the tracks were observed. The numbers of the tracks at the ion energies of 200 and 300 eV agreed with the ion dose, while less tracks were observed at the ion energies of 100 and 150 eV. At 50 eV, no tracks were seen. It has been found that the threshold energy for displacement is below 100 eV for the present ion/target combination.