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Retention characteristics of 3D NAND Flash cells are investigated at various temperatures ( ${T}$ ) depending on the degree of program and erase. The $\Delta {V}_{\text {th}}$ for each condition is compared to understand the degradation of the retention characteristics attributable to vertical loss and/or lateral diffusion. In addition, the relationship between Program/Erase (PE) window (PGM ${V}_{\text {th}}$ – Erase ${V}_{\text {th}}$ ) and $\Delta {V}_{\text {th}}$ are analyzed. In the case when PGM ${V}_{\text {th}}$ is the same, the $\Delta {V}_{\text {th}}$ decreases as the PE window decreases. At temperatures below 150 °C, $\Delta {V}_{\text {th}}$ and PE window show linear relationship, and as PE window decreases, $\Delta {V}_{\text {th}}$ also decreases to 0. On the other hand, at 250 °C, $\Delta {V}_{\text {th}}$ has a non-zero value even if PE window decreases to 0, thus has a non-linear relationship. The measurement results show that the lateral diffusion has a great influence on the short-term retention of 3D NAND flash cells.

We report on the development of a high-resolution and highly efficient beamline for soft-X-ray resonant inelastic X-ray scattering (RIXS) located at Taiwan Photon Source. This beamline adopts an optical design that uses an active grating monochromator (AGM) and an active grating spectrometer (AGS) to implement the energy compensation principle of grating dispersion. Active gratings are utilized to diminish defocus, coma and higher-order aberrations as well as to decrease the slope errors caused by thermal deformation and optical polishing. The AGS is mounted on a rotatable granite platform to enable momentum-resolved RIXS measurements with scattering angle over a wide range. Several high-precision instruments developed in house for this beamline are briefly described. The best energy resolution obtained from this AGM-AGS beamline was 12.4 meV at 530 eV, achieving a resolving power 42,000, while the bandwidth of the incident soft X-rays was kept at 0.5 eV. To demonstrate the scientific impacts of high-resolution RIXS, we present an example of momentum-resolved RIXS measurements on a high-temperature superconducting cuprate, La$_{2-x}$Sr$_x$CuO$_4$. The measurements reveal the A$_{1g}$ apical oxygen phonons in superconducting cuprates, opening a new opportunity to investigate the coupling between these phonons and charge density waves., 9 pages, p figures, submitted to J. of Synchrotron Radiation. Revise expression

Four synaptic devices are introduced for spiking neural networks (SNNs) and deep neural networks (DNNs). Unsupervised learning is successfully demonstrated by applying the STDP learning rule reflecting the LTP/LTD characteristics of the fabricated TFT-type NOR flash memory cells. Gated Schottky diode (GSD) and vertical NAND flash cell are proposed as synaptic device for DNNs. Using matched simulation, we obtained higher learning accuracy with GSD and NAND synaptic devices compared to that with a memristor-based synapse. Measured synaptic properties of the vertical NAND cells are reported for the first time.

A new space program (PGM) scheme is proposed to achieve reliable triple-level-cell (TLC) 3-D NAND flash memory. Considering the lateral diffusion issue of stored electrons in the nitride storage layer, the proposed scheme stores electrons in the nitride layer of the space region between adjacent cells to suppress the lateral movement of trapped electrons in the programmed target cells. The effect of the space PGM can be sustained until 104 s at 90 °C and up to 1k read cycles at 25 °C. The programmed space region of the nitride layer improves the retention characteristics of the cells in the PGM state by 40% and remarkably reduces the V th redistribution.

Super-steep switching is successfully demonstrated using positive feedback (PF) in fabricated diode-type 3-D NAND flash memory strings. Thanks to the PF, the subthreshold swing (SS) measured in a cell of a string during read operation is less than 1 mV/dec at turn-on voltage (V on ) regardless of the polarity and the amount of the charge stored in the cell. This string has memory characteristics similar to conventional FET-type string while keeping much better SS than that of the FET-type string even after program/erase (P/E) cycling.

Charge spreading behavior within a few seconds, referred to as early retention, was comprehensively investigated in 24 word-line stacked tube-type 3D NAND flash memory. We thoroughly explored the charge spreading behavior from the perspectives of both electron and hole spreading in 3D NAND flash memory with different charge trap layer thicknesses at various programming and erasing levels for solid and checkerboard patterns to provide guidelines for minimizing and optimizing the charge spreading.