Observation of stabilized negative capacitance effect in hafnium-based ferroic films

A negative capacitance (NC) effect has been proposed as a critical pathway to overcome the Boltzmann tyranny’ of electrons, achieve the steep slope operation of transistors and reduce the power dissipation of current semiconductor devices. In particular, the ferroic property in hafnium-based films with fluorite structure provides an opportunity for the application of the NC effect in electronic devices. However, to date, only a transient NC effect has been confirmed in hafnium-based ferroic materials, which is usually accompanied by hysteresis and is detrimental to low-power transistor operations. The stabilized NC effect enables hysteresis-free and low-power transistors but is difficult to observe and demonstrate in hafnium-based films. This difficulty is closely related to the polycrystalline and multi-phase structure of hafnium-based films fabricated by atomic layer deposition or chemical solution deposition. Here, we prepare epitaxial ferroelectric Hf_0.5Zr_0.5O₂ and antiferroelectric ZrO₂ films with single-phase structure and observe the capacitance enhancement effect of Hf_0.5Zr_0.5O₂/Al₂O₃ and ZrO₂/Al₂O₃ capacitors compared to that of the isolated Al₂O₃ capacitor, verifying the stabilized NC effect. The capacitance of Hf_0.5Zr_0.5O₂ and ZrO₂ is evaluated as -17.41 and -27.64 pF, respectively. The observation of the stabilized NC effect in hafnium-based films sheds light on NC studies and paves the way for low-power transistors.