Conduction mechanism effect on physical unclonable function using Al₂O₃/TiO_X memristors

In this study, we evaluate the performance of a physical unclonable function (PUF) using Al₂O₃/TiO_x based memristors. Through a conduction mechanism analysis, it is confirmed that the distribution of high-resistance state (HRS) is wider than that of low-resistance state (LRS) due to the direct-tunneling gap. Furthermore, cycle-to-cycle variation and random telegraph noise (RTN) characteristics which can affect the reliability of the PUF are also analyzed. Since the switching characteristics of the devices are less affected by temperature in the LRS thanks to ohmic conduction, the device state of a whole array is determined as the LRS for a better reliability. In addition, three kinds of response extraction methods are compared by evaluating the diffuseness and uniqueness with 2 × 2 switch block for the improved randomness. Finally, the reliability of the PUF is verified considering the measured conductance dependency on temperature and noise effect, and the bit error rates are compared between two states.