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

December, 2020Dec 20, 2021HIGHLIGHTSVol.20 No.12

    December, 2020 | Volume 20, No. 12
  • Article 2020-12-31

    Availability of indirect atmospheric plasma from a dielectric barrier discharge device on biofilm-forming bacteria

    Na J.H., Lee J.-G., Hong S.-C. et al.
    Curr. Appl. Phys. 2020; 20(12): 1307-1313

    Abstract : An investigation of the treatment effect of atmospheric cold plasma (ACP)-generated reactive oxygen species (ROS) against problematic bacteria of chronic wounds is presented. To study ROS effects specifically, a vacuum chamber with a flowmeter to control the background gas composition and a mesh electrode for a dielectric barrier discharge (DBD) device were used. In addition, a numerical modeling was developed to simulate the amount of ROS flux transported from the mesh electrode to determine which of the ROS species was the main factor in the treatment effect. Considering the experimental and computational results and the effective transport distance of each species, ozone could be the main factor in the experimental results. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Local mismatch and noise investigation for pre and post multilayer pHEMTs

    Alim M.A., Jahan I., Nipu N.J. et al.
    Curr. Appl. Phys. 2020; 20(12): 1314-1320

    Abstract : The key objective of this study is to investigate the local mismatch of pre and post multilayer structure on the active devices. Five pre and post multilayer structure pHEMTs on the same wafer within the same cell between adjacent devices are considered. As the study of local mismatch ensures good yields and a way to gain insights about the technology various comparisons are made including the effects of multilayer structuring. The threshold voltage, built-in potential and the net doping concentration of the 2-DEG of the devices are extracted through capacitance-voltage data. The underlying electrical parameter of the transistors as well as the RF figure of merit has been analyzed. The microwave noise related parameters namely minimum noise figure, associate gain, noise resistance, magnitude of the optimum reflection are also discussed and investigated. Centre-to-edge mismatch results in minor variation in performance between devices. These studies would help within the advancement of solid, proficient and low cost generation of future compact structure in 3-D multilayer MMICs. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Thermally stable AgCu alloy disc array for near infrared filters

    Im H.-S., Sim K.-B., Seong T.-Y.
    Curr. Appl. Phys. 2020; 20(12): 1321-1327

    Abstract : We investigated the thermal and optical characteristics of AgCu alloy disc (250 and 380 nm in diameter) arrays to produce an optical filter with low near infrared (NIR) transmittance, and compared their properties with those of Ag disc array. Unlike the Ag discs, the AgCu discs remained relatively stable with hillocks after annealing at 500 °C. The Ag and AgCu disc samples had similar transmittance characteristics, showing a global minimum at ~767 nm (for the 250 nm-disc samples) and at ~1081 nm (for the 380 nm-disc samples). Based on finite-difference time-domain (FDTD) simulations, the global minimum was related to localised surface plasmon resonance (LSPR). The Maxwell-Garnett model was employed to interpret the red-shift of the transmittance minima. The calculations showed that a mixture of agglomerated and stable Ag discs, resulting in different n and k values, would be responsible for the red-shift and an increase in the minimum transmittance. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Mobility of magnetic helicoid in holmium nano-layer

    Zavornitsyn R.S., Naumova L.I., Milyaev M.A. et al.
    Curr. Appl. Phys. 2020; 20(12): 1328-1334

    Abstract : Spin valves with holmium layers and three-layer structures metal/Ho/metal were prepared by magnetron sputtering. A holmium layer in the spin valves is polycrystalline with weak axial texture. The structural coherence length along the hexagonal c-axis is approximately 2/5 of the total thickness of the holmium layer. Field dependences of the spin valves magnetoresistance were measured at different temperatures. Correlation was revealed between magnetic state in holmium layer and the shape of magnetoresistive curve. Deviation of magnetic moments of the reference layer and the adjacent part of holmium from the applied magnetic field was investigated. The field induced mobility of the magnetic helicoid in holmium layers was revealed. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Influence of cavity geometry towards plasmonic gap tolerance and respective near-field in nanoparticle-on-mirror

    Devaraj V., Lee J.-M., Oh J.-W.
    Curr. Appl. Phys. 2020; 20(12): 1335-1341

    Abstract : In this work, we emphasize the importance of cavity geometry along with nanoparticle shape and plasmonic nanogap (based on a nanoparticle on a metallic film (NPOM) design) which plays significant role in understanding the complex plasmonic mode characteristics involving nanoparticle and gap mode resonances. The cross-section imprint of planar cavity on metallic film plays decisive role in near field enhancement properties at similar NP size and plasmonic nanogap conditions for spherical and cubical NPOM systems. By mimicking the NPOM structure to metal-insulator-metal design, we understand the resonant emission differences for the respective plasmonic modes. Influence of dominant and weaker gap mode resonances resulted in an interesting optical behavior (fluctuations in near field enhancement strength) in NP mode in case of cubical nanostructures. By such extensive investigation and interpretation of sub-wavelength complex plasmonic mode characteristics, various practical applications in plasmonics field can be accomplished. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Influence of hetero-gate dielectrics on short-channel effects in scaled tunnel field-effect transistors

    Chien N.D., Vinh L.T., Hong Tham H.T. et al.
    Curr. Appl. Phys. 2020; 20(12): 1342-1350

    Abstract : In this study, we examined the influence of using hetero-gate dielectrics (HGDs) on the short-channel effects (SCEs) in scaled tunnel field-effect transistors (TFETs). For bulk TFETs, the short-channel performance is not influenced by the HGD engineering because the SCEs are caused by the tunneling at the region with negligible gate control. However, the use of the HGD increases the SCEs in double-gate TFETs because the HGD reduces the gate control on the channel. When the HGD optimized in term of on-current is used, the channel of HGD-TFETs is about 10-nm longer than that of uniform-gate dielectric TFETs to obtain similar SCEs. The SCEs in HGD-TFETs can be improved by locating the drain-side heterojunction toward the drain and/or increasing the ratio of low- and high-k equivalent oxide thicknesses. Due to the trend of scaling transistors, an appropriate design of HGD to minimize the SCEs in scaled HGD-TFETs is also crucial. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Modeling and analysis of the effects of inhomogeneous carrier distributions in InGaN multiple quantum wells

    Ryu H.-Y.
    Curr. Appl. Phys. 2020; 20(12): 1351-1358

    Abstract : It is well known that carrier distribution in InGaN multiple quantum wells (MQWs) can be significantly inhomogeneous. However, the conventional ABC recombination model assumes that carriers are uniformly distributed throughout the MQW. In this paper, a modified ABC model that considers the unequal carrier density in the QWs was developed. From the analysis of the developed ABC model, the effective recombination coefficients and modified internal quantum efficiency (IQE) were obtained for an arbitrary carrier distribution in MQWs. The efficiency droop was found to be aggravated as the carrier distribution was increasingly inhomogeneous. However, it was also found that the effect of inhomogeneous carrier distribution alone was not sufficient to explain the IQE droop with the theoretical Auger recombination coefficient based on indirect Auger processes. The developed ABC model is expected to provide insight into the influence of inhomogeneous carrier distributions in MQWs on the efficiency droop in GaN-based light-emitting diodes. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Effects of UV-ozone treatment on the electronic structures of F8BT and PFO polymeric thin films

    Choi S., Kim W., Shin W. et al.
    Curr. Appl. Phys. 2020; 20(12): 1359-1365

    Abstract : The property changes of polymeric films upon degradation are important to develop strategies to prolong the device lifetimes. In this regard, we investigated the effects of ultraviolet-ozone (UVO) treatment on the electronic structures of poly (9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) and poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) films. We found that as the UVO treatment time increased, the intensities of the UV–vis and photoluminescence spectra of both F8BT and PFO films exponentially decayed owing to the destruction of the conjugated system of the films. As per the X-ray photoelectron spectra, both the F8BT and PFO films showed significant oxidation and p-doping effects upon UVO treatment. In addition, UVO treatment caused the etching of the polymeric films, and their thickness gradually decreased; the etching rate with UVO treatment was faster for PFO than for F8BT. These results indicate that the functionalization of polymers with UVO treatment requires the careful consideration of the resulting changes in their electronic structure. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Absorbance and energy levels for a Fe3+ ion in α-Al2O3. Optical pumping applied to a 31 GHz maser

    Mrad M., Tarhini A., Giordano V.
    Curr. Appl. Phys. 2020; 20(12): 1366-1372

    Abstract : The structure of 3d5 configuration ion in a trigonal field is theoretically determined on the basis of a 252×252 matrix of complete energy. The spectra of paramagnetic electron resonance and the optical absorption of the Fe3+ ion in sapphire crystal (α−Al2O3) have been calculated by diagonalizing the matrix of total energy. The obtained results are in good agreement with experimental observations. The strength of probability transitions between energy levels pairs are also established to show the possibility for achieving the inversion of the population in the fundamental state when applying the optical pumping mechanism to the crystal. The results based on the computed parameters of transition and on the maser effect equations show that a maser signal of a 31 GHz can be generated and that depends on the cryogenic design of the resonator. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Improved properties & fatigue resistant behaviour OF Ba(Zr0.15Ti0.85)O3 ferroelectric ceramics

    Mahesh M.L.V., Pal P., Prasad V.V.B. et al.
    Curr. Appl. Phys. 2020; 20(12): 1373-1378

    Abstract : The microstructure, dielectric and piezoelectric properties of Zr doped BaTiO3 ceramics sintered at optimum temperature, are investigated. High energy ball milling technique is adopted to realize nano-sized powders of Ba(Zr0.15Ti0.85)O3 ceramics. Increased boundary mobility of fine powders aided to obtain a relative density of >98.8% of theoretical density corresponding to ceramics under study. Internal stresses in these ceramics are found to be relieved by grain-boundary sliding. The Ba(Zr0.15Ti0.85)O3 ceramics synthesized at relatively low sintering temperatures exhibit remarkable, enhanced dielectric properties viz. improved polarization, high unipolar strain values comparable to Zr doped BaTiO3 single crystals of same composition, at relatively lower electric fields and also exhibit better fatigue tolerant properties. The underlying mechanisms responsible for superior dielectric, ferroelectric and piezoelectric properties are discussed. © 2020 Korean Physical Society

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  • Article 2020-12-31

    Effects of Ca2+ ion substitution on the structure and magnetism of SrRuO3: Elusive magnetism

    Zhang W.-Y., Yue C.-X., Zhao D.-W. et al.
    Curr. Appl. Phys. 2020; 20(12): 1379-1385

    Abstract : SrRuO3 is an orthogonally distorted perovskite (Pbnm) structure whose ferromagnetism is often viewed as an itinerant ferromagnet. Although SrRuO3 has been studied for more than half a century, its structure, magnetism and transport properties are still poorly understood. In this paper, the structure and magnetic evolution of SrRuO3 are discussed in depth through the substitution of Ca2+ for Sr2+ at A sites. The results show that as the Ca substitution increases, the lattice constant decreases, the orthogonal distortion becomes larger, and the saturation magnetization MS, Curie temperature TC and Weiss temperature θp decrease accordingly. Eventually, the ferromagnetic SrRuO3 changes to paramagnetic CaRuO3. The critical exponent β of samples with different substitution contents was obtained by fitting the experimental results, and the value for SrRuO3 (β = 0.55) was similar to that obtained by mean field theory. However, the value increases with the substitution x of Ca, which can't be explained by any scaling theory. The results show that the increase in the value of β is related to the magnetic disorder caused by different magnetic interactions. Analysis using the Rhodes-Wohlfarth criterion indicates that Sr1-xCaxRuO3 has both itinerant-electron and localized-electron magnetism, which is consistent with the theoretical predictions. © 2020 Korean Physical Society

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  • Article 2020-12-31

    TEOS-based low-pressure chemical vapor deposition for gate oxides in 4H–SiC MOSFETs using nitric oxide post-deposition annealing

    Moon J.H., Kang I.H., Kim H.W. et al.
    Curr. Appl. Phys. 2020; 20(12): 1386-1390

    Abstract : The use of SiO2/4H–SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) can be problematic due to high interface state density (Dit) and low field-effect mobility (μfe). Here, we present a tetra-ethyl-ortho-silicate (TEOS)-based low-pressure chemical vapor deposition (LPCVD) method for fabricating the gate oxide of 4H–SiC MOSFETs using nitric oxide post-deposition annealing. SiO2/4H–SiC MOS capacitors and MOSFETs were fabricated using conventional wet and TEOS oxides. The measured effective oxide charge density (Qeff) and Dit of the TEOS-based LPCVD SiO2/4H–SiC MOS capacitor with nitridation were 4.27 × 1011 cm−2 and 2.99 × 1011 cm−2eV−1, respectively. We propose that the oxide breakdown field and barrier height were dependent on the effective Qeff. The measured μfe values of the SiO2/4H–SiC MOSFETs with wet and TEOS oxides after nitridation were, respectively, 11.0 and 17.8 cm2/V due to the stable nitrided interface between SiO2 and 4H–SiC. The proposed gate stack is suitable for 4H–SiC power MOSFETs. © 2020 Korean Physical Society

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December, 2020
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