A 6.5 nm thick anti-ferroelectric HfAlO x film for energy storage devices with a high density of 63.7 J cm-3

In this work, we experimentally demonstrate comprehensively optimized anti-ferroelectric HfAlO (x) films, achieving high saturated polarization charge density and doping concentration in doped-HfO2 films. This allowed us to produce an ultrathin anti-ferroelectric energy storage device with high energy storage density (ESD). With the optimized deposition temperature of 300 degrees C, Hf:Al ratio of 18:1 and an electrode of tungsten, a 6.5 nm thick anti-ferroelectric HfAlO (x) film is realized with a high ESD of 63.7 J cm(-3), which is the thinnest anti-ferroelectric film among all the reported works, associated with such a high ESD. This not only provides an effective way to improve the scaling ability of anti-ferroelectric HfAlO (x) films, but also demonstrates a new approach to strengthen the control of the phase transition.