DEPTH-SENSITIVE VISUALIZATION OF IRRADIATION-INDUCED COLUMNAR DEFECTS IN THE LAYERED SUPERCONDUCTOR 2H-NBSE2 VIA SCANNING PROBE MICROSCOPY

For the first time irradiation-induced columnar defects have been visualized in a classical superconductor by means of scanning probe microscopy (SPM). These defects manifest themselves as hillocks or hollows in atomic-force microscope (AFM) images, depending on the scan direction. Using lateral-force microscopy (LFM) the observed structures can be identified as higher lateral forces within the defects. Depth-dependent measurements show that the mean diameter of the tracks decreases inside the NbSe2 crystals as a result of a reduction of the electronic energy loss S(e). The comparison of magnetization measurements before and after the irradiation with 500 MeV I-127 show an enhancement of the critical current density as it is known for pinning active columnar defects in high-T(c) materials after the irradiation with swift heavy ions.