Abstract
We have developed a low energy focused ion beam (FIB) system by employing retarding field optics. The system is equipped with a gas jet and is used for ion beam assisted etching or deposition. To evaluate the usefulness of low energy FIB, we have been investigating defects in GaAs induced by irradiation of low energy Ga+ FIB and Ar+ unfocused beams. Defets induced by irradiation at 300 K were observed even at a depth of >2000 Å, which is much deeper than the ion range. However, it was observed that the deep distribution was suppressed by irradiation at low temperature (100 K.