Contrast reversal in electron beam-induced current imaging of carbon nanotube devices governed by secondary electron emission

Electron beam-induced current (EBIC) is a vital characterization technique for promising semiconducting single-walled carbon nanotube (CNT) devices, yet its underlying imaging mechanism remains poorly understood. This study elucidates the EBIC imaging mechanism in CNTs. By simultaneously analyzing secondary electron (SE) and EBIC signals at landing energies of 1 keV and 10 keV in scanning electron microscopy (SEM), it is demonstrated that the EBIC signal is strongly correlated with SE emission intensity. This finding indicates that, unlike traditional three-dimensional semiconductor materials where EBIC imaging is dominated by built-in potential, the Pd-CNT system is governed by substrate charging polarity and electron dose. Moreover, the signal intensity distribution is determined by the resistance gradient along the CNT. This fundamental clarification of the physical origin of EBIC in CNTs provides the essential mechanistic foundation required for the reliable quantitative analysis of electrical properties at nanoscale interfaces in low-dimensional electronics.