The cylindrical devices with tunable positive, infinite, and negative capacitance for dynamic random access memory

The capacitance behavior of the ultra-thin ferroelectric/dielectric (FE/DE) stacked devices in the nanoscale cylindrical structure deviated from the negative capacitance (NC) state to unpredicted other states. This work confirmed that the ultra-thin (2.0–3.0 nm) FE Hf _0.33 Zr _0.67 O ₂ layer could have a positive capacitance, infinite capacitance, or NC by controlling the thickness of the stacked DE Al ₂ O ₃ layer thickness (1.0–3.0 nm). Detailed analytical model and numerical simulation based on phase-field modeling, considering the FE polarization bound charge compensation by the injected/trapped interfacial carriers and the geometry effect of the cylinder, precisely identified the change of the inhomogeneous stray field energy, which played a crucial role in determining the capacitance state. Further analysis of the models revealed that the capacitance variation is strongly correlated to the extent of the initial polarization charge compensation of the ferroelectric domains. This work provides guidelines for developing the next-generation capacitors in dynamic random access memory.