3D c-AFM Imaging of Conductive Filaments in HfO2 Resistive Switching Devices
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Abstract
Resistive switching in metal-insulator-metal devices is promising as an alternative to flash memory. The change in resistance from insulating to conducting and back again is theoretically caused by the formation and partial destruction of conductive filaments composed of a metal or oxide structure. These filaments have a significant effect on device performance and stability. However, due to their small size (nm range) and location within the device, the filaments are difficult to study directly. Various techniques such as TEM, SEM, and c-AFM have been used to obtain 2D or 3D images of the filaments in an attempt to determine their morphology, conductivity, and composition. In this study, AFM and c-AFM were used to investigate the topography and local conductivity of the oxide layer and construct a 3D image of a conductive filament in formed p+Si|HfO2|Cu devices. Damage to the oxide layer was found to vary with both oxide crystallinity and forming voltage, conductive regions were found to be associated with the damaged areas, and the 3D data collected for the filament revealed an hourglass morphology.
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hafnium oxide, resistive switching, conductive atomic force microscopy