Fig. 2
Investigation of e-beam induced changes in the Cu film–PI system. Inverse pole figure maps and the inset of (111) pole figures of (a) unirradiated and (b) e-beam-irradiated Cu thin films obtained from ASTARTM analysis and (c) the grain-size distribution in each case. d The critical normal force (Lcr) extracted from a nanoscratch test measuring the normal force at the Cu–PI interface at the onset of delamination. The relative value of work of adhesion (W) between irradiated and unirradiated samples was then calculated, showing better adhesion for the irradiated sample. e The electron energy loss spectroscopy data collected from different positions at 5 nm intervals across the Cu–PI interface for the unirradiated (left) and irradiated (right) samples. Red lines are the raw data, and black lines are their averages over 20 neighboring points. The probe positions are denoted on the high-angle annular dark field scanning transmission electron microscopy images. Error bars represent the standard deviation (c, d). Scale bars, 200 nm (a, b); 50 nm (e)
