Insertion of Dielectric Interlayer: A New Approach to Enhance Energy Storage in HfₓZr1-xO₂ Capacitors

In this letter, we demonstrate an effective way to enrich the performance of HfxZr1-x O2 (HZO) energy storage capacitors (ESCs) by inserting Al2O3 dielectric interlayer (DIL) in the middle of HZO in TiN/HZO/TiN structure. The impact of DIL (1 Å, 5 Å and 10 Å) is investigated in three different HZO compositions [1:1, 1:2 and 1:3]. Irrespective of HZO composition, insertion of DIL at critical thickness enhances the energy storage density (ESD) and efficiency of the ESCs. Grazing incident X-ray diffractometer (GIXRD) analysis reveals that Al2O3 DIL controls the grain size of the HZO films resulting in lower energy dissipation by controlling the linearity of the hysteresis loop. At 4.5 MV/cm, the best ESD ~55 J/cm
³
with ~68% efficiency is achieved for HZO [1:2] capacitors at a critical Al2O3 thickness of 1 Å which is ~35% and ~55% enhanced as compared to that without DIL [~41 J/cm
³
, ~44%]. The best efficiency of ~88% is achieved [ESD ~26 J/cm
³
] for HZO [1:3] capacitors at a critical DIL thickness of 10 Å. The HZO [1:2] ESC with 1 Å DIL displays robust thermal stability in 25 °C to 200 °C temperature range. Moreover, the aforesaid ESCs demonstrate excellent electrical stability even after 10
⁹
times of electric field cycling. Highest ESD of ~70 J/cm
³
at ~50% efficiency is achieved for the same ESC when operated at 6.0 MV/cm. The results obtained herein provide a new strategy to achieve high performance ESCs and can be of significant scientific importance.