# EBIC Imaging of Conductive Paths Formed in Graphene Oxide as a Result of Resistive Switching
## 1 Introduction  
The electron-beam-induced current (EBIC) method is a powerful tool for the characterization of electronic devices and analysis of their failure and/or degradation [1, 2, 3, 4]. In semiconductors, EBIC is capable of revealing extended defects, evaluating their recombination activity, and determining excess carrier diffusion length. The interpretation of EBIC data in semiconductor structures with a p/n junction or a Schottky barrier is rather straightforward, as the mechanisms of the EBIC image formation are well understood [3, 5, 6]. In the work of [7, 8], EBIC was successfully used for visualization of the leakage current sites in the gate dielectrics of field effect transistors. However, the EBIC images obtained on the devices with insulating layers can be governed by different and/or additional operative mechanisms, and thus require additional efforts for correct interpretation [7, 8, 9, 10, 11]. The frequently observed effect of electron-beam-induced charging in the insulating layers [12, 13, 14, 15, 16] makes interpretation of the EBIC images even more difficult. Recently, owing to a growing interest in the development of insulator-based resistive random access memory (RRAM), the EBIC method was used in several research works to monitor conductive paths in metal-oxide-based structures [17, 18, 19, 20, 21]. RRAM devices are of significant importance owing to their potential implementation in energy-efficient single-bit memory arrays and/or in multi-bit systems required to create adaptive neuromorphic networks [22, 23, 24]. However, despite significant progress in the development of resistive memory devices, their practical use is limited by a number of unsolved problems. The most significant problem is a lack of a clear understanding of the operative mechanisms responsible for resistive switching even in metal oxides, such as HfO\({}_{2}\), Ta\({}_{2}\)O\({}_{5}\), ZnO, and TiO\({}_{2}\), which are the most intensively studied RRAM materials. It is commonly believed that resistiveswitching in metal oxides is determined by the formation of nanoscale conductive filaments as a result of the motion of oxygen vacancies and/or metal cations [25]. Although several works focused on studying conductive filament formation have been performed using advanced methods such as transmission electron microscopy [26], scanning transmission X-ray microscopy [27], and scalpel scanning probe microscopy [28], a comprehensive picture of the underlying physical mechanism of filament formation has not yet been developed. To explore the origin and dynamics of conductive filament formation in Pt-TiO\({}_{2}\)-Pt structures, the EBIC method was successfully employed in [11]. By measuring the EBIC current as a function of the beam energy and a special device geometry, the authors attempted to assess the contribution of various competing currents to the measured EBIC signal. As the values of the competing currents in metal-insulator-metal (MIM) structures are of the same order of magnitude as the beam current, it is difficult to unambiguously deconvolute the sources of the measured current and deconstruct a cumulative effect of hot electrons, parasitic leakage, built-in field inversion, and other factors. Metal-insulator-semiconductor (MIS) structures appear to be more suitable for investigations of resistive switching by EBIC, as the concentration of the excess carriers generated inside a semiconductor substrate is orders of magnitude higher than that of the primary electrons. Therefore, the contribution of the other competing currents to the measured current will be negligible. An additional advantage of MIS structures is an opportunity for quantitative evaluations of both the generation rates and the concentrations of the excess carriers [29]. This assessment is supported by EBIC visualization of leakage current sites in the gate dielectrics of field effect transistors [7; 8] and of the conductive paths formed during resistive switching in graphene oxide (GO)-based MIS structures [21].