Enhancing Physical Randomness in Ta₂O₅/HfO₂ Based Memristors through Electrode Engineering for True Random Number Generation

True random number generators (TRNGs) based on memristors utilize inherent switching variability to generate unpredictable true random numbers. Herein, the performance and instability of Ta2O5/HfO2/Pt based memristors induced by their top electrodes are investigated. With Ag, Ta, and Pt as their top electrodes, Ta2O5/HfO2/Pt based memristors exhibit volatility, bipolarity, and unipolarity, respectively, which correspond to different conduction mechanism models. The intrinsic stochastic characteristics can be leveraged in various TRNG circuits, especially enhancing the throughput rate and continuity of circuits by utilizing unipolar Pt/Ta2O5/HfO2/Pt devices. Notably, under optimized conditions, the TRNG based on the unipolar device achieves a throughput rate of approximately 160 kb/s, and the generated true random numbers passed all 15 NIST SP 800-22 randomness tests. This work not only realizes a TRNG with a unipolar memristor as its core entropy source but also underscores the significance in securing encrypted transmission for Internet of Things applications.