Integration of Ultrathin Hafnium Oxide with a Clean van der Waals Interface for Two-Dimensional Sandwich Heterostructure Electronics.

Integrating high-κ dielectrics with a small equivalent oxide thickness (EOT) with two-dimensional (2D) semiconductors for low-power consumption van der Waals (vdW) heterostructure electronics remains challenging in meeting both interface quality and dielectric property requirements. Here, we demonstrate the integration of ultrathin amorphous HfO sandwiched within vdW heterostructures by the selective thermal oxidation of HfSe precursors. The self-cleaning process ensures a high-quality interface with a low interface state density of 10-10 cm eV.

Quasi-Zero-Dimensional Ferroelectric Polarization Charges-Coupled Resistance Switching with High-Current Density in Ultrascaled Semiconductors.

Ferroelectric memristors hold immense promise for advanced memory and neuromorphic computing. However, they face limitations due to low readout current density in conventional designs with low-conductive ferroelectric channels, especially at the nanoscale. Here, we report a ferroelectric-mediated memristor utilizing a 2D MoS nanoribbon channel with an ultrascaled cross-sectional area of <1000 nm, defined by a ferroelectric BaTiO nanoribbon stacked on top.

A Light-Programmed Rewritable Lattice-Mediated Multistate Memory for High-Density Data Storage.

Mainstream non-volatile memory (NVM) devices based on floating gate structures or phase-change/ferroelectric materials face inherent limitations that compromise their suitability for long-term data storage. To address this challenge, a novel memory device based on light-programmed lattice engineering of thin rhenium disulfide (ReS ) flakes is proposed. By inducing sulfur vacancies in the ReS channel through light illumination, the device's electrical conductivity is modified accordingly and multiple conductance states for data storage therefore are generated.

Reconfigurable Quasi-Nonvolatile Memory/Subthermionic FET Functions in Ferroelectric-2D Semiconductor vdW Architectures.

The functional reconfiguration of transistors and memory in homogenous ferroelectric devices offers significant opportunities for implementing the concepts of in-memory computing and logic-memory monolithic integration. Thus far, reconfiguration is realized through programmable doping profiles in the semiconductor channel using multiple-gate operation. This complex device architecture limits further scaling to match the overall chip requirements.

Charge-Ferroelectric Transition in Ultrathin Na Bi Ti O Flakes Probed via a Dual-Gated Full van der Waals Transistor.

Ferroelectric field-effect transistors (FeFETs) have recently attracted enormous attention owing to their applications in nonvolatile memories and low-power logic electronics. However, the current mainstream thin-film-based ferroelectrics lack good compatibility with the emergent 2D van der Waals (vdW) heterostructures. In this work, the synthesis of thin ferroelectric Na Bi Ti O (NBIT) flakes by a molten-salt method is reported.

Self-Terminated Surface Monolayer Oxidation Induced Robust Degenerate Doping in MoTe for Low Contact Resistance.

We introduce an effective method to degenerately dope MoTe by oxidizing its surface into the p-dopant MoO in oxygen plasma. As a self-terminated process, the oxidation is restricted only in the very top layer, therefore offering us an easy and efficient control. The degenerate p-doping with the hole concentration of 2.

Quantum Dot Formation in Controllably Doped Graphene Nanoribbon.

We introduce the controllable doping from hydrogen silsesquioxane (HSQ) to graphene by changing its electron-beam exposure dose. Using HSQ as the dopant, a fine-resolution electron-beam resist allows us to selectively dope graphene with an extremely high spatial resolution of a few nanometers. Therefore, we can design and demonstrate the single quantum dot (QD)-like transport in the graphene nanoribbon (GNR) with the opening of the energy gap.

High-Pressure Synthesis, Crystal Structure, and Magnetic Properties of Sr2MnO3F: A New Member of Layered Perovskite Oxyfluorides.

We have successfully synthesized Sr2MnO3F, a new layered perovskite oxyfluoride with a n = 1 Ruddlesden-Popper-type structure using a high-pressure, high-temperature method. Structural refinements against synchrotron X-ray diffraction data collected from manganese oxyfluoride demonstrated that it crystallizes in a tetragonal cell with the space group I4/mmm, in which the Mn cation is located at the octahedral center position. This is in stark contrast to the related oxyhalides that have square-pyramidal coordination such as Sr2MO3X (M = Fe, Co, Ni; X = F, Cl) and Sr2MnO3Cl.

Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors.

The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors.

High-pressure synthesis, crystal structures, and magnetic properties of 5d double-perovskite oxides Ca2MgOsO6 and Sr2MgOsO6.

Double-perovskite oxides Ca2MgOsO6 and Sr2MgOsO6 have been synthesized under high-pressure and high-temperature conditions (6 GPa and 1500 °C). Their crystal structures and magnetic properties were studied by a synchrotron X-ray diffraction experiment and by magnetic susceptibility, specific heat, isothermal magnetization, and electrical resistivity measurements. Ca2MgOsO6 and Sr2MgOsO6 crystallized in monoclinic (P21/n) and tetragonal (I4/m) double-perovskite structures, respectively; the degree of order of the Os and Mg arrangement was 96% or higher.

High-pressure synthesis, crystal structure, and magnetic properties of KSbO-type 5 oxides KOsO and BiOsO.

5 Solid-state oxides KOsO (Os; 5) and BiOsO (Os; 5) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500-1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5 electronic properties and tunnel-like structure motifs were investigated. A KSbO-type structure with a space group of -3 and -3 was determined for KOsO and BiOsO, respectively.

High-temperature ferrimagnetism driven by lattice distortion in double perovskite Ca2FeOsO6.

5d and 3d hybrid solid-state oxide Ca2FeOsO6 crystallizes into an ordered double-perovskite structure with a space group of P2₁/n with high-pressures and temperatures. Ca2FeOsO6 presents a long-range ferrimagnetic transition at a temperature of ~320 K (T(c)) and is not a band insulator, but is electrically insulating like the recently discovered Sr2CrOsO6 (T(c) ~725 K). The electronic stat of Ca2FeOsO6 is adjacent to a half-metallic state as well as that of Sr2CrOsO6.