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

Abstract

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. Particularly, the ferroic property in hafnium-based films with fluorite structure provides an opportunity for the application of NC effect in electronic devices. However, up to now, only transient NC effect has been confirmed in hafnium-based ferroic materials, which is usually accompanied with hysteresis and detrimental to low power operations of transistors. The stabilized NC effect enables the hysteresis-free and low power transistors, but has never been observed and demonstrated in hafnium-based films. Such an absence 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 Hf0.5Zr0.5O2and antiferroelectric ZrO2films with single-domain structure and observe the capacitance enhancement effect of Hf0.5Zr0.5O2/Al2O3 and ZrO2/Al2O3 capacitors than that of the isolated Al2O3capacitor, verifying the stabilized NC effect. The capacitance of Hf0.5Zr0.5O2and ZrO2is evaluated as –17.41 and –27.64 pF, respectively. The observation of stabilized NC effect in hafnium-based films sheds light on the NC studies and paves an avenue to the low-power transistors.

Large Polarization Near 50 μC/cm2 in a Single Unit Cell Layer SrTiO3

“…Delicate design of the material structure or composition to achieve extraordinary performance or precise control of physical properties is the trend of future research in advanced electronic devices. − Here, we design a viable strategy for integrating large strains and strong interfacial coupling that also successfully decreases the restriction of out-of-plane depolarization fields by using in-plane domain structures. Consequently, a highly polar SrTiO 3 is stabilized by this strategy, which exhibits large tetragonality (∼1.05), notable polar ion displacement (0.019 nm), and thus ultrahigh spontaneous polarization (up to ∼50 μC/cm 2 ).…”