Light-induced negative differential resistance effect in a resistive switching memory device

January, 2020Jan 09, 2020HIGHLIGHTSVol.20 No.3

    December, 2019 | Volume 20, No. 3
  • 2019-12-30

    Light-induced negative differential resistance effect in a resistive switching memory device

    Wang X., Wang Y., Feng M. et al.
    2019; 20(3): 371-378

    Abstract : The negative differential resistance (NDR) effect was observed in a Pt/BiFeO3/TiO2/BiFeO3/Pt memory cell by using light-illumination as extra stimulation. Further, the coexistence appearances and gradually becomes obvious when the device is exposed to light-illumination, which display an excellent stability and reversibility of the coexistence of NDR and resistive switching (RS) at room temperature. Through analysis of the physical conduction mechanism, it is expected that a large number of photo-generated charge carriers are induced under light-illumination on the surface and interface of the heterojunction is responsible for the appearance of this coexistence phenomenon. Importantly, the NDR effect is strengthened by the competition transfer of charge carrier in the polarized electric field under light-illumination. This work shows that the coexistence of light-modulated NDR and RS can deeply explore the potential applications of light-controlled multifunctional devices. © 2019 Korean Physical Society

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  • 2019-12-30

    Examination of high-throughput hybrid calculations using coarser reciprocal space meshes

    Park J.-S.
    2019; 20(3): 379-383

    Abstract : High-throughput density functional theory calculations have been typically performed with reduced accuracy and notable error in the band gap. Here we suggest several approaches to calculate the optoelectronic properties by using coarser k-point meshes for the Fock exchange potential. In our benchmark calculations, we were able to obtain the optical properties of zinc-blende and wurtzite materials with reasonable accuracy. We also propose an approach of high-throughput calculations using a pre-converged wavefunction by the reduced k-point meshes for the Fock exchange and performing the subsequent non-self-consistent-field calculations. © 2019

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  • 2020-01-07

    FDTD simulation of the optical properties for a gold nanoparticle-over-nanosheet hybrid structure

    Chen Y., Wang J., Xu T. et al.
    2020; 20(3): 391-399

    Abstract : The optical properties of a two-dimensional gold nanoparticle-over-nanosheet (2D-AuNP/NS) have been studied using Finite-Difference Time-Domain (FDTD) method. 2D-AuNP/NS hybrid structure exhibits three typical localized surface plasmon (LSP) resonances, which occur in nanogaps between NP-NP, NP-NS and coupled upper and lower surface of NS respectively. Thus, the influence of AuNP-size, surface AuNP-coverage, NP-NP-spacing and NS-thickness on the localized electric field was analyzed in details. The LSP resonance between NP-NS has been predicted to be the most important effect on SERS, which is dominant, stable and can maintain the SERS intensity even at a relatively low NP-coverage. If a slight deviation of AuNPs away from their original periodic positions was permitted, a disordered model was then constructed which would more closely approximate the real AuNP/NS hybrid structure and was able to calculate the influence of disorder on LSP resonance. A blue shift (rather than red shift) of the resonance peak was observed and its peak intensity would increase first and decrease then with the increase of NP-NP-spacing. FDTD simulations have finally illustrated that NP-coverage should be controlled ranging from 80.0 % to 87.0% or just equal to 100%, if both AuNP-size and NP-thickness is controlled to 10 nm. The FDTD simulation results are qualitative agreement with the existing experimental data and are very useful in the future materials designs for AuNS-based nanocomposite. © 2019

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  • 2020-01-07

    Study on the thermoelectric properties of porous Bi-Te films deposited using thermal evaporation on AAO template

    Liu S., Li G., Lan M. et al.
    2020; 20(3): 400-405

    Abstract : The application of thermoelectric films is limited to retain the temperature gradient. In this study, the Bi-Te films are deposited on the AAO template with a pore size of 100 nm using thermal evaporation. The results show that the conductive types of the Bi-Te film are tuned by source temperature. The power factor of the p-type porous film decreases 36% by comparing to that of the p-type nonporous film (1020 μW/mK2 at 250 °C). Meanwhile, the temperature difference in the porous device is maintained and is approximately 5.0 °C. Thus, the maximum output power is achieved in the porous device (about 25 pW), which is 5 times higher than that of the nonporous device. This provides a method to improve the conversion efficiency of thermoelectric film device by maintaining the temperature difference by using porous structure. © 2020 Korean Physical Society

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  • 2020-01-08

    A multi-scale model linking microstructure and macro electric behaviors of ferroelectric field effect transistor

    Jiang L., Feng X., Ming H. et al.
    2020; 20(3): 406-412

    Abstract : A multi-scale model linking microstructure and macro electric properties of ferroelectric field effect transistor (FeFET) is established based on the phase field method and Maxwell's total current law. The simulation results confirm that the channel current of FeFET is modulated by local interface ferroelectric domains which are easily affected by the microstructure. Using the developed transistor model, we investigate the effects of location of dislocation sites on hysteresis behavior of ferroelectric film and electric behavior of FeFET. Interfacial dislocations have strong effects on hysteresis behavior than internal dislocations since the former can induce imprint behavior while the latter only reduce the coercive field. However, due to the c-domains at the interface, the effects of interfacial and internal dislocations on FeFET electrical properties are the exact opposite. The interfacial dislocations just increase the voltage required to toggle the channel while the internal dislocations can induce disappearance of the FeFET memory window. © 2020 Korean Physical Society

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  • 2020-01-08

    Spin-orbit coupling-induced band inversion and spin Chern insulator phase in plumbene and stanene

    Lee K.W., Lee C.E.
    2020; 20(3): 413-418

    Abstract : Z2 topology in two-dimensional group IVA materials has been explained by the band orders due to the crystal field splitting at the Γ point in the Brillouin zone, while spin-orbit coupling (SOC) was considered just to open a band gap. By using a multi-orbital tight-binding model, we show that the SOC induces band inversion between the conduction and valence bands at the Γ point in plumbene, which also is the case in stanene when the SOC strength increases. As a result of the band inversion, plumbene becomes a spin Chern insulator with a spin Chern number CS = 2 and, as the SOC strength increases, stanene undergoes a topological phase transition from a Z2 topological insulator to a spin Chern insulator with CS = 2. Under a staggered AB-sublattice potential, plumbene undergoes a phase transition from the spin Chern insulator with CS = 2 to a Z2 topological insulator with CS = 1. © 2020 Korean Physical Society

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  • 2020-01-08

    Sensible design of open-porous spherical architectures for hybrid supercapacitors with improved high-rate capability

    Lee B.-G., Shin S.-I., Ha M.-W. et al.
    2020; 20(3): 419-424

    Abstract : Hybrid supercapacitors show high energy densities with good long-term cycling stability when used as energy sources. However, their poor rate performance as a consequence of their low ionic diffusion capability at high currents during cycling should be improved. Here, we propose using a spray-drying process to fabricate a novel structure comprising open-porous spherical lithium manganese oxide as an electrode material for hybrid supercapacitors. The resultant hybrid supercapacitor comprising full-cell systems shows a high specific capacitance (33.8 F cm−3 at a current of 1 A) and remarkable high-rate performance (25.6 F cm−3 at a current of 16 A). Moreover, outstanding cycling stability of 83% was attained at a current of 2 A after 5400 cycles. Our new strategy provides a useful methodology to increase the abundance of electrochemically active sites by fabricating a spherical structure using nanosized primary particles, which also leads to shorter diffusion pathways and to improved ionic electron transport because of the open-porous structure of the electrode materials. © 2020

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  • 2020-01-09

    ZnO/Ag/ZnO multilayer transparent electrode for highly-efficient ITO-Free polymer solar cells

    Xu R., Yang K., Zang Y.
    2020; 20(3): 425-430

    Abstract : Ultrathin metal film (UTMF) with a ZnO/Ag/ZnO hybrid structure was used as transparent electrode in a high-efficiency bulk heterojunction system for the fabrication of ITO-free polymer solar cells. The performance of the devices was carefully tuned through optical simulation using transfer matrix method by varying the thickness of ZnO seed layer and thin absorber layer. By employing appropriate device architecture, polymer solar cells fabricated using this UTMF-based electrode show efficiency as high as 9.49%, which is slightly higher compared to that of ITO-based device. From good agreement between the external quantum efficiency and optical modeling, it was found that the optimized microcavity configuration formed in UTMF-based device can greatly enhance the absorbance of the BHJ layer at longer wavelength as well as the favored exciton distribution for better charge transport and collection. © 2020

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  • 2020-01-10

    Rectifying resistance switching behaviors of SnO2 microsphere films modulated by top electrodes

    Yuan R., Xia W., Xu M. et al.
    2020; 20(3): 431-437

    Abstract : Based on the bipolar resistive switching (RS) characteristics of SnO2 films, we have fabricated a new prototypical device with sandwiched structure of Metal/SnO2/fluorine-doped tin oxide (FTO). The SnO2 microspheres film was grown on FTO glass by template-free hydrothermal synthesis, which was evaporated with various commonly used electrodes such as aluminium (Al), silver (Ag), and gold (Au), respectively. Typical self-rectifying resistance switching behaviors were observed for the RS devices with Al and Au electrodes. However, no obvious rectifying resistance switching behavior was observed for the RS device with Ag electrode. Above results were interpreted by considering the different interface barriers between SnO2 and top metal electrodes. Our current studies pave the ways for modulating the self-rectifying resistance switching properties of resistive memory devices by choosing suitable metal electrodes. © 2020 Korean Physical Society

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  • 2020-01-10

    Influence of Ag thickness on the structural, optical, and electrical properties of the SnS/Ag/SnS trilayer films for solar cell application

    Arepalli V.K., Nguyen T.D., Kim J.
    2020; 20(3): 438-444

    Abstract : We fabricated the SnS/Ag/SnS (SAS) trilayer thin films by a sputtering method at 200 °C. The structural, optical, and electrical properties of the films were studied by varying the Ag interlayer thickness from 9 to 27 nm. The EDS analysis revealed that all SAS trilayer films showed an increase in the atomic percentage of Ag from 1.87 to 6.18. The X-ray diffraction studies confirmed that SAS films with Ag-18 nm thickness showed a preferred (111) peak of the SnS with improved crystallinity. The optical absorption coefficient of the SAS films increased by a factor of 18 when compared to the SnS films without Ag. Also, the optical band gap decreased from 1.53 to 1.28 eV with Ag thickness. All SAS films exhibited the p-type conductivity with increased hole-concentration from 1.94 × 1014 to 4.15 ×1018cm−3 and also the mobility from 1.31 to 81.6 cm2. V−1s−1. © 2020 Korean Physical Society

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  • 2020-01-13

    Photocurrent spectra for above and below bandgap energies from photovoltaic PbS infrared detectors with graphene transparent electrodes

    Kim J., Ampadu E.K., Oh E. et al.
    2020; 20(3): 445-450

    Abstract : We discussed photocurrent spectra of photovoltaic PbS infrared detectors using multi-layer graphene as transparent electrode, where p-PbS films were deposited on TiO2/FTO substrates by chemical bath deposition. In the photocurrent spectra, we observed both above-bandgap and sub-bandgap photocurrent without any external bias. We discussed impurity band model and grain boundary model in order to explain the sub-bandgap photocurrent near 15 μm. Since FTO is transparent in the visible range, we were able to illuminate green laser beam from the FTO back-side, and photo-response up to 50 μm was found to be enhanced. This long wavelength photo-response was attributed to the excitation of the photo-electrons accumulated at the TiO2/PbS interface. Our photovoltaic PbS devices can detect not only short-infrared but also terahertz radiation at room temperature, which is highly applicable to various fields. © 2020 Korean Physical Society

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  • 2020-01-14

    Quantum interference effect in few-layered transition metal dichalcogenide

    Park J., Yoshida K., An S.J. et al.
    2020; 20(3): 451-455

    Abstract : Van der Waals layered transition metal dichalcogenides (TMDCs), as atomically flat two-dimensional materials, have been studied extensively in both fundamental science and application fields in recent years. The reduced-dimensional properties of TMDCs not only provide a route for the fabricating of efficient field effect transistors and optoelectronic devices but also suggest the possibility of the devices that utilize quantum coherency. In this work, we characterize the electron transport properties of ReS2, one of the TMDCs, at both room temperature and low temperature. Of particular note, we measured strong quantum conductance oscillations as a function of the gate voltages and source-drain voltages at reduced temperature, which is evidence of quantum coherent transport. This work unambiguously establishes ReS2 as a promising candidate for future quantum materials. © 2020

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January, 2020
Vol.20 No.3

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