No abstract

Resistive random access memories can potentially open a niche area in memory technology applications by combining the advantages of the long endurance of dynamic random‐access memory and the long retention time of flash memories. Recently, resistive memory devices based on organo‐metal halide perovskite materials have demonstrated outstanding memory properties, such as a low‐voltage operation and a high ON/OFF ratio; such properties are essential requirements for low power consumption in developing practical memory devices. In this study, a nonhalide lead source is employed to deposit perovskite films via a simple single‐step spin‐coating method for fabricating unipolar resistive memory devices in a cross‐bar array architecture. These unipolar perovskite memory devices achieve a high ON/OFF ratio up to 108 with a relatively low operation voltage, a large endurance, and long retention times. The high‐yield device fabrication based on the solution‐process demonstrated here will be a step toward achieving low‐cost and high‐density practical perovskite memory devices.

Recently, two-dimensional materials such as molybdenum disulfide (MoS2) have been extensively studied as channel materials for field effect transistors (FETs) because MoS2 has outstanding electrical properties such as a low subthreshold swing value, a high on/off ratio, and good carrier mobility. In this study, we characterized the electrical and photo-responsive properties of MoS2 FET when stacking a p-type organic copper phthalocyanine (CuPc) layer on the MoS2 surface. We observed that the threshold voltage of MoS2 FET could be controlled by stacking the CuPc layers due to a charge transfer phenomenon at the interface. Particularly, we demonstrated that CuPc/MoS2 hybrid devices exhibited high performance as a photodetector compared with the pristine MoS2 FETs, caused by more electron-hole pairs separation at the p-n interface. Furthermore, we found the optimized CuPc thickness (∼2 nm) on the MoS2 surface for the best performance as a photodetector with a photoresponsivity of ∼1.98 A W(-1), a detectivity of ∼6.11 × 10(10) Jones, and an external quantum efficiency of ∼12.57%. Our study suggests that the MoS2 vertical hybrid structure with organic material can be promising as efficient photodetecting devices and optoelectronic circuits.

We investigated the effect of irradiation on molybdenum disulfide (MoS2) field effect transistors with 10 MeV high-energy proton beams. The electrical characteristics of the devices were measured before and after proton irradiation with fluence conditions of 10(12), 10(13), and 10(14) cm(-2). For a low proton beam fluence condition of 10(12) cm(-2), the electrical properties of the devices were nearly unchanged in response to proton irradiation. In contrast, for proton beam fluence conditions of 10(13) or 10(14) cm(-2), the current level and conductance of the devices significantly decreased following proton irradiation. The electrical changes originated from proton-irradiation-induced traps, including positive oxide-charge traps in the SiO2 layer and trap states at the interface between the MoS2 channel and the SiO2 layer. Our study will enhance the understanding of the influence of high-energy particles on MoS2-based nanoelectronic devices.

memories, and organic field-effect transistors (OFETs), have various advantages including mechanical flexibility, low cost, solution-processed fabrication, and tunable material functionalities by molecular design compared with silicon-based materials. [1][2][3][4][5][6][7][8][9][10][11][12][13] However, the contact resistance problem arising between organic materials and metal electrodes has been one of the dominant obstacles for adopting organic semiconducting devices instead of silicon-based devices. Diverse attempts, for instance, self-assembled monolayer (SAM) treatment on metal electrodes, [14][15][16][17][18][19] inserting a charge injection layer between OSC and metals, [20][21][22][23][24][25][26][27] choice of metals for better injection properties, [28,29] adopting carbon-based conductor like graphene as electrodes, [30] have been introduced to improve carrier injection across typically a non-ohmic contact. Especially, considering large operation voltages required for OFETs, improving contact properties of organic/metal interface is an essential step for practical applications of OSCs.Contact doping is one of the most effective techniques to reduce contact resistance and has been widely employed in silicon-based devices and recently in OSCs to reduce the contact resistance. [31][32][33][34][35][36] In order to avoid undesirable OFF currents, it needs to be performed selectively, i.e., in localized regions at the source-drain contacts only and not in the channel region. The doped regions have been usually confined to the top surface of the OSC film by depositing a small amount of dopants on the top of the organic film by thermal evaporation. As a result, the position of the gate dielectrics was normally restricted to the top side of devices (i.e., FETs in a top-gate structure) in order to enhance the charge injection from metal electrodes to the accumulation layer formed on the top surface of the polymer. [31,32] Recently, the combination of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 -TCNQ) as host and dopant material, respectively, has produced a highly conducting polymer that has been studied as a candidate for a synthetic metal and high power-factor thermoelectric material. [37][38][39][40][41] Interestingly, this combination achieved an efficient bulk-doping of PBTTT by solid-state diffusion which implied that the F 4 -TCNQ Organic semiconductors (OSCs) have been widely studied due to their merits such as mechanical flexibility, solution processability, and large-area fabrication. However, OSC devices still have to overcome contact resistance issues for better performances. Because of the Schottky contact at the metal-OSC interfaces, a non-ideal transfer curve feature often appears in the low-drain voltage region. To improve the contact properties of OSCs, there have been several methods reported, including interface treatment by self-assembled monolayers and introducing charge injection layers. Here, a selectiv...

We report the electrical properties of synthesized large-area monolayer molybdenum disulfide (MoS2) field-effect transistors (FETs) with low-cost inkjet-printed Ag electrodes. The monolayer MoS2 film was grown by a chemical vapor deposition (CVD) method, and the top-contact Ag source/drain electrodes (S/D) were deposited onto the films using a low-cost drop-on-demand inkjet-printing process without any masks and surface treatments. The electrical characteristics of FETs were comparable to those fabricated by conventional deposition methods such as photo- or electron beam lithography. The contact properties between the S/D and the semiconductor layer were also evaluated using the Y-function method and an analysis of the output characteristic at the low drain voltage regimes. Furthermore, the electrical instability under positive gate-bias stress was studied to investigate the charge-trapping mechanism of the FETs. CVD-grown large-area monolayer MoS2 FETs with inkjet-printed contacts may represent an attractive approach for realizing large-area and low-cost thin-film electronics.

Number of metastatic LN was a significant prognostic factor, in addition to the N stage. Therefore, number of metastatic LN must be considered for postoperative staging system to tailor treatment and follow-up recommendations. In addition, patients with ≥2 metastatic LN may benefit from total thyroidectomy and RAI therapy with postoperative follow-up with serum thyroglobulin.

We studied noise characteristics of a nanocomposite of polyimide (PI) and phenyl-C61-butyric acid methyl ester (PCBM) (denoted as PI:PCBM), a composite for the organic nonvolatile resistive memory material. The current fluctuations were investigated over a bias range that covers various intermediate resistive states and negative differential resistance (NDR) in organic nanocomposite unipolar resistive memory devices. From the analysis of the 1/f(γ) type noises, scaling behavior between the relative noise power spectral density S̃ and resistance R was observed, indicating a percolating behavior. Considering a linear rate equation of the charge trapping-detrapping at traps, the percolation behavior and NDR could be understood by the modulation of the conductive phase fraction φ with an external bias. This study can enhance the understanding of the NDR phenomena in organic nanocomposite unipolar resistive memory devices in terms of the current path formation and the memory switching.