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Organometal halide perovskites have emerged as potential material systems for resistive memory devices besides their outstanding optical and electrical properties. Although halide‐perovskite resistive memory has the advantage of operating with a low voltage and large on/off ratio, random distribution in operation voltage remains a challenge in memory application. This stochastic operation characteristic is due to the random formation of conducting filaments that cause resistance fluctuations in the material. Therefore, it is essential to investigate the formation and dissolution of conducting filaments and their structure. However, direct observation of a nanoscale filamentary structure is often challenging. Moreover, detailed studies of conducting filaments in halide‐perovskite materials have rarely been reported. By employing a scaling theory with a fractal structure, this study investigates the geometric structures and dynamics of conducting filaments formed in organometal halide perovskite through current noise analysis. The temperature‐dependent electrical properties and current noise demonstrate the role of ion migration in the formation of conducting filaments. The findings could enhance the understanding of the resistive switching phenomena of perovskite resistive memory devices in terms of percolative conducting filaments. Thus, providing a route for achieving a stable memory operation by controlling the relevant structure and dynamics of the switching processes. [ABSTRACT FROM AUTHOR]

Abstract: Organic resistive memory devices are one of the promising next‐generation data storage technologies which can potentially enable low‐cost printable and flexible memory devices. Despite a substantial development of the field, the mechanism of the resistive switching phenomenon in organic resistive memory devices has not been clearly understood. Here, the time–dependent current behavior of unipolar organic resistive memory devices under a constant voltage stress to investigate the turn‐on process is studied. The turn‐on process is discovered to occur probabilistically through a series of abrupt increases in the current, each of which can be associated with new conducting paths formation. The measured turn‐on time values can be collectively described with the Weibull distribution which reveals the properties of the percolated conducting paths. Both the shape of the network and the current path formation rate are significantly affected by the stress voltage. A general probabilistic nature of the percolated conducting path formation during the turn‐on process is demonstrated among unipolar memory devices made of various materials. The results of this study are also highly relevant for practical operations of the resistive memory devices since the guidelines for time‐widths and magnitudes of voltage pulses required for writing and reading operation can be potentially set. [ABSTRACT FROM AUTHOR]

In the past decade, considerable progress has been made in the field of organic electronic devices toward understanding charge transport processes and developing practical device applications. In addition, the electronic noise in organic electronic devices has been extensively studied along with the progress, providing a deep understanding of their electronic phenomena. This review article presents a summary of electronic noise analyses on various organic electronic devices to determine the usefulness of such analyses toward comprehending the operation of organic electronic devices. We expect that the noise analyses presented in this article will contribute to more meaningful insights for advancing organic electronic devices. [ABSTRACT FROM AUTHOR]

The energy consumption during the operation of organic nonvolatile memory devices fabricated on a flexible polyethylene naphthalate (PEN) substrate is investigated. For bistable resistive memory devices, the applied external voltage and time are essential factors for switching the memory cell from the OFF to ON state because the amounts of voltage and time determine the applied energy needed to set the memory cell. Using the composite material polyimide (PI) and [6,6]‐phenyl‐C61 butyric acid methyl ester (PCBM) as the active layer of the bistable resistive memory devices on a flexible PEN substrate, nonvolatile unipolar switching behavior and good electrical reliability of PI:PCBM memory devices are observed, and the relationship between the applied energy and the switching characteristics for various applied voltages and times is characterized. The results of the performed experiments show that higher ON state currents are reached as greater set voltages or times are applied, and reliable switching behavior is observed at over ≈10−6 J of applied energy with at least 4 V of applied voltage and 10 ms of pulse time. [ABSTRACT FROM AUTHOR]

We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS2) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS2 and pentacene. The pentacene/MoS2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices. [ABSTRACT FROM AUTHOR]

One of the long-standing problems in the field of organic electronics is their instability in an open environment, especially their poor water resistance. For the reliable operation of organic devices, introducing an effective protection layer using organo-compatible materials and processes is highly desirable. Here, we report a facile method for the depositing of an organo-compatible superhydrophobic protection layer on organic semiconductors under ambient conditions. The protection layer exhibiting excellent water-repellent and self-cleaning properties was deposited onto organic semiconductors directly using a dip-coating process in a highly fluorinated solution with fluoroalkylsilane-coated titanium dioxide (TiO 2 ) nanoparticles. The proposed protection layer did not damage the underlying organic semiconductors and had good resistance against mechanical-, thermal-, light-stress-, and water-based threats. The protected organic field-effect transistors exhibited more-reliable electrical properties, even when exposed to strong solvents, due to its superhydrophobicity. This study provides a practical solution with which to enhance the reliability of environmentally sensitive organic semiconductor devices in the natural environment.

Grain boundaries in a chemical vapour deposition (CVD)-grown monolayer of MoS 2 induce significant effects on the electrical and low frequency noise characteristics of the MoS 2 . Here, we investigated the electrical properties and noise characteristics of MoS 2 field effect transistors (FETs) made with CVD-grown monolayer MoS 2 . The electrical and noise characteristics of MoS 2 FETs were analysed and compared for the MoS 2 channel layers with and without grain boundaries. The grain boundary in the CVD-grown MoS 2 FETs can be the dominant noise source, and dependence of the extracted Hooge parameters on the gate voltage indicated the domination of the correlated number-mobility fluctuation at the grain boundaries. The percolative noise characteristics of the single grain regions of MoS 2 were concealed by the noise generated at the grain boundary. This study can enhance understanding of the electrical transport hindrance and significant noise generation by trapped charges at grain boundaries of the CVD-grown MoS 2 devices.

We investigated the current-voltage and noise characteristics of two-dimensional (2D) monolayer molybdenum disulfide (MoS 2 ) synthesized by chemical vapor deposition (CVD). A large number of trap states were produced during the CVD process of synthesizing MoS 2 , resulting in a disordered monolayer MoS 2 system. The interface trap density between CVD-grown MoS 2 and silicon dioxide was extracted from the McWhorter surface noise model. Notably, generation-recombination noise which is attributed to charge trap states was observed at the low carrier density regime. The relation between the temperature and resistance following the power law of a 2D inverted-random void model supports the idea that disordered CVD-grown monolayer MoS 2 can be analyzed using a percolation theory. This study can offer a viewpoint to interpret synthesized low-dimensional materials as highly disordered systems.

We fabricated 8 × 8 arrays of non-volatile resistive memory devices on commercially available Scotch ® Magic ™ tape as a flexible substrate. The memory devices consist of double active layers of Al 2 O 3 with a structure of Au/Al 2 O 3 /Au/Al 2 O 3 /Al (50 nm/20 nm/20 nm/20 nm/50 nm) on attachable tape substrates. Because the memory devices were fabricated using only dry and low temperature processes, the tape substrate did not suffer from any physical or chemical damage during the fabrication. The fabricated memory devices were turned to the low resistance state at ∼3.5 V and turned to the high resistance state at ∼10 V with a negative differential resistance region after ∼5 V, showing typical unipolar non-volatile resistive memory behavior. The memory devices on the tape substrates exhibited reasonable electrical performances including a high ON/OFF ratio of 10 4 , endurance over 200 cycles of reading/writing processes, and retention times of over 10 4 s in both the flat and bent configurations.

We present the integration of flexible and microscale organic nonvolatile resistive memory devices fabricated in a cross-bar array structure on plastic substrates. This microscale integration was made via orthogonal photolithography method using fluorinated photoresist and solvents and was achieved without causing damage to the underlying organic memory materials. Our flexible microscale organic devices exhibited high ON/OFF ratio (I(ON/I(OFF) > 10(4)) under bending conditions. In addition, the ON and OFF states of our flexible and microscale memory devices were maintained for 10,000 seconds without any serious degradation.

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.

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 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.

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.