Pohang University of Science and Technology · Engineering
Professor Seungyeol Oh's research lab specializes in advanced ferroelectric materials, particularly HfZrO₂ (HZO)-based thin films, for next-generation nanoelectronics and neuromorphic computing. The lab focuses on optimizing ferroelectric properties such as polarization switching, endurance, and interface engineering to enable non-volatile multi-level memory devices and energy-efficient synaptic transistors. Key research directions include material integration with CMOS processes, structural engineering for high-k dielectrics, and pulse-driven device operation for applications in AI hardware and DRAM technology.
Figures are computed from collected data and may differ slightly.
We propose a HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> (HZO)-based ferroelectric synapse device with multi-levels states of remnant polarization that is equivalent to multi-levels conductance states. By optimizing the pulse condition, we obtained 32 levels of remnant polarization states for both potentiation and depression. Furthermore, a ferroelectric field-effect transistor is simulated using the obtained multiple remnan
Ferroelectric materials are promising candidates for synaptic weight elements in neural network hardware because of their nonvolatile multilevel memory effect. This feature is crucial for their use in mobile applications such as inference when vector matrix multiplication is performed during portable artificial intelligence service. In addition, the adaptive learning effect in ferroelectric polarization has gained considerable research attention for reducing the CMOS circuit overhead of an integ
In this study, we investigate the effects of various electrodes on the ferroelectric properties of ultrathin HfZrOx (HZO) films. The ferroelectric polarization is totally suppressed in the HZO films with TiN and W bottom electrodes when the film thickness is below 5 nm. These results can be attributed to the formation of a dead layer at the bottom electrode/HZO interface during the atomic layer deposition (ALD) and annealing processes. On the other hand, the HZO film with a Pt bottom electrode s
We investigate the effects of high-pressure hydrogen annealing (HPHA) on W/ferroelectric Al:HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /interface layer (IL)/Si stacks. With HPHA, degradation in remnant polarization is observed in the pristine state due to ferroelectric domain pinning. However, after wake-up, a comparable remnant polarization is observed by domain de-pinning. In addition, HPHA improves the quality current and low int
This study evaluates HfxZr1-xO2 (HZO)-based high-k dielectrics, where dielectric constant (k) is significantly enhanced through structural engineering. The investigation focuses on their dielectric characteristics by pulse operation for DRAM applications. HZO/ZrO2 (HZZ) films with different superlattice structures display different dielectric behaviors, including ferroelectricity, morphotropic phase boundary (MPB), and anti-ferroelectricity. The HZZ film at the MPB condition exhibits exceptional
HfxZr1-xO2 thin films exhibit a high dielectric constant at the morphotropic phase boundary (MPB), which is beneficial for high-k dielectric applications. To minimize the equivalent oxide thickness, the effects of various HZO thicknesses and compositions on the MPB were investigated. In general, HZO films with a thickness of 10 nm exhibit a high dielectric constant owing to MPB at a composition of Hf:Zr = 3:7. However, it was confirmed that composition optimization is required for HZO films with
Abstract With the increasing demand for high‐performance computing and storage solutions, industries are under pressure to deliver enhanced‐density, high‐speed, cost‐efficient, and reliable memory technologies. The development of advanced high dielectric constant (high‐k) dielectrics for dynamic random‐access memory (DRAM) remains essential yet challenging, with a need for further advancements on scaling and mass production compatibility. A significant advancement has been the discovery of morph
To improve the turn-off speed and uniformity of atomic threshold switching (TS) devices, we propose the use of the AgSe electrode and controlled bipolar pulse forming method. Compared with TS devices with Ag and AgTe electrodes, TS device with the AgSe electrode shows an extremely fast turn-off speed, which can be explained by the limited injection of Ag into the switching layer. By applying positive bias (Icc=500 nA, 1 ms) followed by negative bias (-0.1 to -0.2 V, 10 μs), the TS device exhibit
It is important to obtain ferroelectric HfZrO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> (HZO) films at low crystallization temperatures to ensure compatibility with low-temperature processes. This study investigates the origin of degradation in ferroelectric properties of ferroelectric films at low crystallization temperatures, by modifying the bottom electrodes and HZO thicknesses. The TiN/HZO/TiN and W/HZO/W stacks exhibit no or very
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