| dc.description.abstract | Ferroelectric memory (FeRAM) can overcome the von Neumann bottleneck due to its excellent durability and operational speed, which enables faster data processing for large-scale calculations, making it a forward-looking component in artificial intelligence computation. Currently, the widely used material for ferroelectric memory is hafnium zirconium oxide thin films (HfO2-ZrO2, SL-HZO), which have attracted attention due to their superior polarization properties, lower variability, and higher switching speed compared to solid solution HfxZr1-xO2 (SS-HZO). Although studies have shown that lattice distortion may lead to strong polarization, a comprehensive physical explanation is still lacking for the relationship between periodic film thick-ness, variability, thermal stability, and retention decay in superlattice structures. In this study, we used XPS and electrical measurements to observe these behaviors and explored the root causes of these reliability issues through first-principles DFT calculations, using ab initio molecular dynamics (AIMD), nudged elastic band (NEB) method, and crystal orbital Hamilton population (COHP) analysis. By comparing defect formation (variability) and thermal stability in HZ2.5, HZ5, HZ7.5, and HZ10, we found: (i) Lower tp and an ordered arrangement of Hf-O and Zr-O atoms can shorten bond lengths, preventing distortion from propagating into the material, and phonon transport favors high-temperature retention. (ii) Larger tp allows SL-HZO to withstand higher stress biases; however, the instability of Zr-O bonds accumulates defects, resulting in higher variability during sweep operations. Experiments indicate that the benefits of A-level stacking exceed those of nanolayer stacking.
Oxide channel materials have become a focal point of research, with indium gallium zinc oxide (IGZO) standing out in particular. IGZO is junction-less due to the near-zero dielectric constant at the interface layer between the channel and oxide, thereby avoiding the electrical degradation issues associated with silicon channels. However, as applications continue to expand and develop, traditional IGZO faces challenges in high-resolution displays and 3D NAND, where higher mobility, low off-current, and excellent coverage are essential. This study uses first-principles calculations to investigate an n-type semiconductor channel material, indium oxide (In2O3), a binary compound with higher mobility and easier scalability than IGZO. Calculations show that this material has an energy gap of 2.27 eV for a monolayer film thickness and a work function of 4.2–5.3 eV, with experimentally measured mobility reaching up to 90 cm2V?1s?1. Additionally, to accommodate different applications, such as the design of bipolar transistors, inverter circuits, and transparent thin-film transistors, we focused on high-mobility wide-bandgap p-type semiconductors. While NiO and Cu?O have been widely studied, their mobilities do not exceed 100 cm2V?1s?1. In this study, we investigated two-dimensional tellurium oxide (TeO?), which has a monolayer energy gap of 3.79 eV, a work function of 3.9–4.3 eV, and a mobility of up to 200 cm2V?1s?1. This study provides a practical design guideline for high-performance ferroelectric memory applications. | en_US |