Electrical stress-induced damage in TiN/Ti/HfO2/W memristors: The critical role of voltage polarity and vacuum condition

In this work, we investigate the damage caused by the catastrophic breakdown of the insulating layer in TiN/Ti/HfO2/W memristors when subjected to ramped voltage stress. Our analysis includes physical and compositional examinations of the damaged regions using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy. These techniques are complemented by in situ SEM current-voltage (I–V) measurements performed under vacuum conditions. In particular, we explored the connection of the applied voltage polarity with the damage onset. We show that high negative voltages applied to the TiN top electrode typically result in worm-like damage patterns. This specific type of damage, along with more severe stages of degradation such as disconnection and melting, is exclusively observed for negative biases and does not occur under vacuum conditions. Conversely, under positive voltage stress, no damage is detected in the top electrode of the devices irrespective of the external conditions. These results highlight the critical role of vacuum in controlling redox-driven compositional changes and preventing catastrophic damage. By systematically analyzing the effects of voltage polarity and ambient conditions, this study provides key insights into damage generation mechanisms. The obtained results pave the way for enhancing the lifetime, reliability, and robustness of memristive technologies for their use in emerging applications.