The influence of Ga+ irradiation on the transport properties of mesoscopic conducting thin films

We studied the influence of 30 keV Ga+-ions-commonly used in focused-ion-beam (FIB) devices-on the transport properties of thin crystalline graphite flakes, and La0.7Ca0.3MnO3 and Co thin films. The changes in electrical resistance were measured in situ during irradiation and also the temperature and magnetic field dependence before and after irradiation. Our results show that the transport properties of these materials strongly change at Ga+ fluences much below those used for patterning and ion-beam-induced deposition (IBID), seriously limiting the use of FIB when the intrinsic properties of the materials of interest are of importance. We present a method that can be used to protect the sample as well as to produce selectively irradiation-induced changes.