Field Of Memory Devices Research Articles

Pressure-Induced Reversible and Irreversible Multistate Switching in NiAs-Type Chromium Selenides

Materials capable of switching in multiple states under external stimuli have garnered extensive attention in the field of memory devices and switches. The coupling of various switching properties is of paramount significance to the creation of multifunctional devices. Herein, we report the pressure-induced multiswitching behaviors of both the structural and physical properties in two chromium selenides, CrSe and Cr2Se3. Comprehensive high-pressure characterizations reveal the collaborative occurrence of pressure-induced structural phase transitions, spin-crossover, metallization, and n–p conduction-type switching in both compounds. Upon compression, Cr2Se3 demonstrates an unexpected increase in resistivity and band gap, which is associated with the disordering of the self-intercalation structure. Of particular interest is that due to the dimensional differences in crystal structures, the photoelectric properties of the two decompressed samples are inversely regulated after pressure treatment. Notably, the band gap of Cr2Se3 is pronouncedly broadened after decompression due to the partially irreversible disorder in the structure. These results demonstrate that pressure engineering can regulate the photoelectric properties of materials effectively and flexibly, serving as a potential foundation for fabricating innovative pressure-responsive multifunctional devices.

Electric field induced tunable memristive characteristics of exfoliated graphene oxide embedded polymer nanocomposites

Resistive switching properties of layered graphene oxides (GOs) filled polymer nanocomposites (PNCs) have received tremendous attention in the field of memory devices. Herein, we report highly stable write-once-read-many-times (WORM) resistive switching properties of exfoliated GOs embedded poly(methyl methacrylate) (PMMA) thin films. The WORM characteristics of the PNC devices have been studied by varying the active layer thickness and the content of GO nanofillers. A disrupted carbon network of GOs enables defect states that act as an energy barrier for carriers and the charge transport through the PNC devices is blocked at a lower electric field. At an elevated electric field, GO sheets embedded PMMA offers percolation pathways for electron transfer, thereby making the composites electrically more conductive. The set voltage (VSET) decreases with a decrease in the active layer thickness, whereas VSET increases with a decrease in the GOs content within PNC devices. For a fixed compliance current (∼1 μA), highest ION/IOFF ratio ∼104 at 1.87 V has been achieved for the PNCs device spin-coated at 9000 rpm with 0.1 wt. % GOs content. The stability of the devices has been confirmed through retention test up to 104 s. In addition, the J-V curves are fitted and an appropriate conduction mechanism is proposed.

Transition metal oxides with triangular metallic sublattices: From multiferroics to low-dimensional magnets

Abstract The very recent studies of two classes of transition metal oxides with a triangular metallic sublattice are reported. The first class of materials concerns the swedenborgite CaBaCo4O7 family, which is shown to be a ferrimagnetic multiferroic with a gigantic-induced electrical polarization, and the second one deals with the spin chain oxides of the Sr4Mn2CoO9 type, which have been found to behave as single chain magnets and single ion magnets. These materials that exhibit a potential for applications in the field of memory devices and quantum computation pave the way for future investigations in these systems.

Observation of temperature effect on electrical properties of novel Au/Bi0.7Dy0.3FeO3/ZnO/p-Si thin film MIS capacitor for MEMS applications

In this work the dependence of electrical properties on operation temperature (27°C to 200°C) of Au-Cr/Bi0.7Dy0.3FeO3 (BDFO)/ZnO/p-Si (MIS device) are discussed. The thin film of BDFO was deposited by pulsed laser deposition (PLD) on p-Si. From the electrical characterization, the devices properties like ideality factor (η), barrier height) (BH) of Au-Cr/BDFO/ZnO/p-Si MIS were determined. The values of η and BH were found to be 1.34 and 0.86eV at 200°C and 2.16 and 0.30eV; respectively, at room temperature (27°C). The leakage current conduction mechanism of the device was investigated and found to be Schottky emission (SE) in the low electric field (<0.92MVcm−1) regime and trap assisted Poole–Frenkel (PF) mechanism for high electric field regime. The coexistence of ferroelectric and ferromagnetic coupling and excellent dielectric properties in multiferroic BDFO offers potential in the field of memory devices; sensing and energy harvesting (cantilevers).

Synthesis of Alternating Copolysiloxane with Terthiophene and Perylenediimide Derivative Pendants for Involatile WORM Memory Device

Alternating copolysiloxane with both electron donor terthiophene and electron acceptor perylenediimide derivative pendants (PTSi‐alt‐PDISi) is synthesized successfully. The polymer exhibits high decomposition and glass transition temperatures, good film‐forming ability, and high morphological stability. The estimated HOMO and LUMO energy levels of PTSi‐alt‐PDISi are –5.77 and –3.90 eV, respectively. The fabricated memory device with the configuration of ITO/PTSi‐alt‐PDISi/Au(Al) shows nonvolatile write‐once‐read‐many‐times (WORM) memory characteristics. Its turn‐on threshold voltage is 1.7 V, while its ON/OFF current density ratio is around 104 in ambient atmosphere. The well‐defined memory property of PTSi‐alt‐PDISi is attributed to the transition of the pendant terthiophene and perylenediimide groups from the disoriented state to the ordered face‐to‐face conformation at the threshold voltage and the charge transfer interaction between pendent terthiophene donor and perylenediimide acceptor moieties, which are confirmed by XRD patterns and fluorescence emission measurement. This suggests that the new donor–acceptor polysiloxanes have potential applications in the field of memory devices.

LDSS research activities in Korea

It has been only about ten years since Korea was recognized as an emerging country in the field of memory devices in the semiconductor industry. When the first GaAs MBE reactor in Korea was installed in 1983, it gave a very special meaning to the physicists, material scientists, and electronics engineers of Korea. The purchase of such a sophisticated machine could be regarded as the starting point of research on low dimensional semiconductor structures (LDSS) in Korea.