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Abstract Methods to encode digital data items as strands of synthetic DNA followed by selective data retrieval have been demonstrated. However, these initially bio‐oriented processes remain slow and not optimized. DNA field‐effect transistor (DNA‐FET) is studied here as a possible random‐access memory (RAM) device for simple, selective and rapid ssDNA fragment retrieval used as data pool identifier. The DNA‐FET is based on a co‐planar Au‐gated fully organic transistor appended with short single‐stranded DNA (ssDNA) probes bearing a blocking molecule to prevent partial hybridization and achieve near perfect selectivity for short length ssDNA (up to 45 nt). Examination of transconductance of the novel active layer incorporating a DNA nanopore architecture reveals enhanced binding site accessibility. This, in turn, facilitates discriminatory hybridization, particularly in the physical retrieval of short‐length ssDNA from a competitive, concentrated ssDNA background pool consisting of nine different sequences, with at least one nucleotide difference. The DNA‐FET exhibits rapid operation (9 min) in the millivolt range, low detection limit (sub‐femtomolar), high selectivity and reusability. Considering the straightforward concept, near error‐free identification capacity and hypothetically outstanding scalability, the DNA‐FET described here has potential as a foundation for further exploration of advanced RAM technology in the DNA data storage process.

Abstract An antiambipolar transistor (AAT) exhibits a negative differential transconductance (NDT) due to a partially overlapped p–n junction formed in the transistor channel. However, the NDT origin remains unclear. In this study, the operando Kelvin probe force microscopy is employed to unveil this issue. When the AAT is turned on, steep potential drops induced by pinch‐off states are visible in the p‐ and n‐type channels. Due to the similarity to the surface potential profiles in the constituent transistors, it is revealed that the pinch‐off points are formed at both edges of the p–n‐stacked layers. This result indicates that the overlapped layers behave like a pseudo‐drain electrode for both transistor channels. Therefore, the AAT drain current can be explained as the overlapped currents in the saturation regions of the p‐ and n‐type transistors. Moreover, the drain current is suppressed when either the p‐ or n‐type channel is completely depleted. The depletion layer formation is responsible for the NDT property. This technique provides a comprehensive understanding of the carrier transport mechanism of AATs, leading to the further evolution of organic electronic circuits.

Abstract A dual‐gate anti‐ambipolar transistor (AAT) with a two‐dimensional ReS2 and WSe2 heterojunction is developed. The characteristic Λ‐shaped transfer curves yielded by the bottom‐gate voltage are effectively controlled by the top‐gate voltage. This feature is applied to logic operations, with the bottom‐ and top‐gate voltages acting as two input signals and the drain current (Id) monitored as an output signal. Importantly, a single dual‐gate AAT exhibits all the two‐input logic operations (AND, OR, XOR, NAND, NOR, and XNOR) under optimized input voltages. Additionally, drain voltage (Vd)‐induced switching between AND and OR logic operations is achieved. These features are advantageous for simplifying circuit design.

Abstract We report on magnetotransport in a high-quality graphene device, which is based on monolayer graphene (Gr) encapsulated by hexagonal boron nitride (hBN) layers, i.e., hBN/Gr/hBN stacks. In the vicinity of the Dirac point, a negative magnetoconductance is observed for high temperatures > ~ 40 K, whereas it becomes positive for low temperatures ≤ ~ 40 K, which implies an interplay of quantum interferences in Dirac materials. The elastic scattering mechanism in hBN/Gr/hBN stacks contrasts with that of conventional graphene on SiO2, and our ultra-clean graphene device shows nonzero magnetoconductance for high temperatures of up to 300 K.

Dark photocatalysis is the ability of a photocatalyst to accumulate photocarriers during light irradiation and consume them for redox reactions under dark conditions. This phenomenon of photocatalysts storing photocarriers is known as charge accumulation. Dark photocatalysts can mitigate fluctuations in photocatalytic reaction efficiency in response to fluctuating solar irradiation. Potassium poly(heptazine imide) (K-PHI) has attracted considerable attention due to its high photocatalytic efficiency and ability to undergo dark photocatalysis. However, the detailed mechanism of charge accumulation in K-PHI remains unclear because photochromism, potassium ion desorption, and charge accumulation occur simultaneously triggered by light irradiation, limiting the comprehensive understanding of this mechanism. To elucidate the charge accumulation mechanism in K-PHI, highly oriented K-PHI thin films were prepared. Then, their fundamental physical properties and optical response of their electrical properties were investigated. We succeeded in separately observing photochromism, potassium ion desorption, and charge accumulation induced by light irradiation on K-PHI and proposed a comprehensive model to explain these phenomena. This study not only provides insights into the unique physical phenomena exhibited by K-PHI but also contributes to the development of solar energy-storage materials in the future. [ABSTRACT FROM AUTHOR]

Acenes are a promising class of organic materials with distinctive electronic and optical properties. Here decaazapentacene and octaazatetracenes are prepared and their self-assembly behaviour at different oxidation states is analysed.

Identifying the properties of spin-states is crucial for understanding the possible magnetic applications of MoS2 thin-film transistors. Here, spin-states of conduction electrons and atomic vacancies in MoS2 are distinguished and investigated under device operation using electron spin resonance.

The solid-state properties of crystalline supramolecular polymers have generally remained unexplored. Herein, we investigated the isothermal crystallization of a supramolecular polymer and showed that, depending on the temperature, it formed distinct structures at a higher hierarchical level. Interestingly, the resulting crystalline forms showed distinct adhesive properties and mechanical-failure modes (adhesive or cohesive). [ABSTRACT FROM AUTHOR]

Semiconductor nanocrystals are potential nanoelectronic materials but often display nonuniform electric properties due to their anisotropic growths. Here, the authors report cross-sectional cathodoluminescence imaging of a single-crystalline ZnO nanowire to resolve its growth sectors with different carrier concentrations.

To elucidate the exciton dynamics at the heteromolecular interface, the temperature dependence of time-resolved photoluminescence (TRPL) spectra of neat-N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) and PTCDI-C8/Quaterrylene (QT) heteromolecular thin films was investigated. The lifetimes of excitons were evaluated to identify the Frenkel (FE), high energy charge-transfer (CTEhigh), low energy charge-transfer (CTElow), and excimer exciton states. The thermal activation energy (Δact) of CTElow in PTCDI-C8 thin film was evaluated as 25 meV, which is 1/5 of that of FE, indicating that CTElow is more thermally sensitive than FE in PTCDI-C8 thin film. We investigated the exciton transport length (l) along the vertical direction against the substrate surface in PTCDI-C8/QT thin film at 30 K, and demonstrated that lFE = 9.9 nm, lCTElow = 4.2 nm, lCTEhigh = 4.3 nm, and lexcimer = 11.9 nm. To elucidate the difference in l among these excitons, the activation energies (Ea) for quenching at the heteromolecular interface were investigated. Ea values were estimated to be 13.1 meV for CTElow and 18.6 meV for CTEhigh. These values agree with the thermal sensitivity of CTEs as reported in a previous static PL study. This latter situation is different from the case of FE and excimer excitons, which are transported via a resonant process and have no temperature dependence. The small Ea values of CTEs suggest that exciton transport takes place via a thermal hopping process in CTEs. The present experimental study provides information on nano-scaled exciton dynamics in a well-defined PTCDI-C8 (2 ML)/QT (2 ML) system.

Nanowires of semiconducting poly(3-hexylthiophene) (P3HT) were produced by a nanochanneltemplate technique. Polymer chain alignment in P3HT nanowires was investigated as a function of nanochannel widths (W) and polymer chain lengths (L). We found that the ratio between chain length and channel width (L/W) was a key parameter as regards promoting polymer chain alignment. Clear dichroism was observed in polarized ultraviolet-visible (UV-Vis) absorption spectra only at a ratio of approximately L/W=2, indicating that the L/W ratio must be optimized to achieve uniaxial chain alignment in the nanochannel direction. We speculate that an appropriate L/W ratio is effective in confining the geometries and conformations of polymer chains. This discussion was supported by theoretical simulations based on molecular dynamics. That is, the geometry of the polymer chains, including the distance and tilting angles of the chains in relation to the nanochannel surface, was dominant in determining the longitudinal alignment along the nanochannels. Thus prepared highly aligned polymer nanowire is advantageous for electrical carrier transport and has great potential for improving the device performance of field-effect transistors. In fact, a one-order improvement in carrier mobility was observed in a P3HT nanowire transistor. [ABSTRACT FROM AUTHOR]

Recent progress in photoactive organic field-effect transistors (OFETs) is reviewed. Photoactive OFETs are divided into light-emitting (LE) and light-receiving (LR) OFETs. In the first part, LE-OFETs are reviewed from the viewpoint of the evolution of device structures. Device performances have improved in the last decade with the evolution of device structures from single-layer unipolar to multi-layer ambipolar transistors. In the second part, various kinds of LR-OFETs are featured. These are categorized according to their functionalities: phototransistors, non-volatile optical memories, and photochromism-based transistors. For both, various device configurations are introduced: thin-film based transistors for practical applications, single-crystalline transistors to investigate fundamental physics, nanowires, multi-layers, and vertical transistors based on new concepts.

Multi-step chemical vapor deposition (CVD) is a synthesis method which is capable of producing a uniform, large area, and high-quality thin films. In this work, we report the effect of post-annealing on the structural and optical properties of fewlayers (FL) MoS2 thin films synthesized by multi-step CVD. Based on atomic force microscopic image, the thickness of the MoS2 thin film is ~3 nm, which is equivalent to five layers. After annealing at 900°C for 17 min, intensity of the A1g and E¹2g Raman modes increased by ~3 times while the full-width-at-half-maximum (FWHM)* reduced from ~10 cm-1 to ~7.5 cm-1 for A1g and from~13.6 cm-1 to~7.5 cm-1 for E¹2g. Both of the as-grown and annealed samples showed Xray (002) diffraction peak at 14.2° but the intensity was more prominent for the annealed sample. It was found that the annealed sample showed clear and distinct absorbance peaks at 666, 615, 448, 401, and 278 nm which correspond to the A, B, C, D, and E excitons, respectively. The results indicate that annealing significantly improved the optical and structural quality of the MoS2 film. Field-effect transistor based on annealed MoS2 thin film was fabricated and showed electron mobility of 0.21 cm²V-1s-1, on/off ratio of 1.3 × 10² and a threshold voltage of 0.72 V. Our work highlights the importance of high-temperature annealing in multi-step CVD to obtain a uniform and high-quality FL MoS2 thin films. [ABSTRACT FROM AUTHOR]

We established a process to develop well-defined polymer nanowire transistors made of liquidcrystalline semiconducting poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2). Nano-scaled channels have been fabricated in gate insulator layers of SiO2 using a lithography technique. The nanochannels offer templates for forming polymer nanowires in which polymer chains are uniaxially aligned along the nanochannels through a nano-confinement effect. In addition, this process prevents the occurrence of serious damage during the inevitable etching process that is used to separate the nanowires from each other. We examined the electrical properties and polymeric chain alignment of F8T2 nanowires. Nanowire transistors exhibited carrier mobilities of 3.5 and 2.8×10-3 cm²/Vs for 54 and 130 nm wide nanowires, respectively. The carrier mobilities were about three times larger than that of a thin film transistor. Polarized UV-vis absorption analysis clarified that the improved carrier mobility can be attributed to the enhanced polymer chain alignment in the nanochannels. This approach has great potential as regards improving device performance, downsizing, and the large-scale integration of nanowire transistors with various kinds of device configurations. [ABSTRACT FROM AUTHOR]

The balance between good solubility and high crystallinity is an advantageous characteristic of 2,6-bis(4-pentylphenylethynyl) anthracene (1). Organic field-effect transistors featuring either a vacuum-deposited film or a simple drop-cast film of 1 both showed high hole mobilities of 0.94 and 0.63 cm²V-1 s-1, respectively. [ABSTRACT FROM AUTHOR]

We synthesized cubic nanoassemblies of octahedral CeO2 nanocrystals by simply heating an aqueous solution of cerium nitrate (Ce(NO3)3) in the presence of hexanedioic acid (HOOC(CH2)4COOH) in a lab-scale plug-flow reactor. It was concluded that the octahedral shape of the primary CeO2 nanocrystals plausibly leads to octa-coordination of the primary nanocrystals, thus enabling controlled assembly to form a cubic structure. [ABSTRACT FROM AUTHOR]

We demonstrate a comprehensive study of self-assembled molecular nanowire, including molecular design, one-dimensional crystal growth, resistivity measurement of individual wire, and application to a field-effect transistor. Appropriate molecular design and control of interfacial interactions lead to single crystalline wire growth with an extensive π-stacking motif. Resistivity measurements of an individual molecular wire indicate that these structural features are advantageous for electrical transport. Finally, field-effect transistors with single- and double-wire channels were fabricated to give some indication of the potential application of the molecular wires. [ABSTRACT FROM AUTHOR]

We report on low temperature carrier transport property of quantum dot (QD) devices based on hexagonal boron nitride-encapsulated tetralayer graphene heterostructures. In the device with single dot geometry, we demonstrate a stochastic Coulomb blockade, suggesting formation of multiple dots coupled each other in series/parallel. Under a perpendicular magnetic field, the overlapping Coulomb diamonds are lifted at zero bias voltage and the charging energy is decreased. These imply the suppression of multiple dots behavior. Our results pave a way toward the investigation of interlayer correlation on single electron transport in few-layer graphene QDs. [ABSTRACT FROM AUTHOR]

Electrolyte-gated-organic field effect transistors (EG-OFETs) functionalized by engineered lipid monolayers (LMLs) are investigated to tune pH sensitivity for sensor application. The EG-OFET functionalized by the OH-terminated LML shows linear dependence on the physiological pH range (4–8). Meanwhile, the LML with polar-head groups presents limited pH sensitivity only in a certain pH range. In contrast, the methyltrichlorosilane passivation of the LML head group makes the EG-OFET non-sensitive in a broad pH range (1.68–12). These findings suggest that our proposed transistors have the potential to construct versatile sensor applications with controllable pH sensitivity. [ABSTRACT FROM AUTHOR]

Photocontrollable ambipolar transistors were developed by using diarylethene (DAE) layers with dibenzo[b,d]thiophene substituents as the transistor channels. An important feature is that both electron transport and hole transport occurred in the transistors upon ultraviolet (UV) light irradiation. The result indicates that the closed-ring isomer in the DAE molecules served as an ambipolar channel. Alternating UV and visible light irradiation controlled both the hole and electron currents, this was accompanied by photoisomerization from the closed-ring (semiconductor) to open-ring isomers (insulator). The light-induced on/off ratios in the drain currents were in the 95–225 range for the hole transport and in the 6–22 range for the electron transport. We found that the energy level alignment between the work function of the electrode and the molecular orbitals of the closed-ring isomer was responsible for the ambipolar transport. Our finding therefore offers a new strategy for developing optoelectronic organic transistors. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to clarify the factors for the stable operation of a poly(3-hexylthiophene) (P3HT)-based water gated organic field effect transistor (WG-OFET). To this end, the influence of the surface morphologies and electrode metals on the transistor properties were investigated. The experimental results indicated that a flat surface improved the on/off ratio and switching repeatability. Treating the surface with a lipid membrane was found to reduce hysteresis loops in the transfer curves probably due to the reduced number of carrier traps. The Au gate electrode effectively lowered the threshold voltage. Consequently, stable transistor operation with a low threshold voltage of 35 mV was achieved by employing a gold gate electrode and lipid membrane treatment. These results suggest that WG-OFETs with an ultra-thin lipid membrane have great potential for sensor applications, and in particular for sensing water-soluble analytes. [ABSTRACT FROM AUTHOR]

The spontaneous polarization effect of ZnO on the thin film growth of pentacene, which is a typical π conjunction organic semiconductor, was investigated. Pentacene thin films were grown on polar ZnO surfaces by ultraslow organic film physical vapor deposition to obtain layer-by-layer growth. X-ray diffraction measurements revealed that pentacene molecules stand upright on polar ZnO surfaces, and that the films consist of two polymorphs, namely, the thin-film and bulk phases. The thin-film phases of pentacene were observed regardless of the polarity of the ZnO substrate at a thickness of less than six molecular layers. However, pentacene on a Zn-polar ZnO substrate gradually changed to the bulk phase unlike that on an O-polar ZnO substrate. Kelvin probe force microscopy measurements revealed that the surface potential of pentacene becomes more positive with increasing pentacene thickness at less than two molecular layers. The variation in the potential of pentacene on the Zn-polar ZnO substrate was larger than that of pentacene on the O-polar ZnO substrate. These findings indicate that the polarity of the semiconductor can control the growth and electronic state of the inorganic/organic semiconductor interface. [ABSTRACT FROM AUTHOR]

The polarity effects of ZnO on the electronic state of a monolayer pentacene/ZnO interface were investigated by X-ray photoelectron spectroscopy (XPS). XPS revealed that the Zn-polar ZnO (Zn-ZnO) strongly depleted electrons in pentacene at the interface. The O-polar ZnO showed greater electron transfer from ZnO to pentacene than Zn-ZnO. The surface potential of pentacene on ZnO was larger than that of bulk pentacene regardless of the ZnO polarity. These findings indicate that the polarity of ZnO has the potential to control the electronic state of the organic/inorganic semiconductor interface. [ABSTRACT FROM AUTHOR]

The rogress of on-surface molecular nanoarchitectonics over the last two decades has been reviewed. Over the early period in the 1990s–2000s, molecular self-assemblies were intensively studied, where van der Waals (vdW) interaction was predominant. After that, in the 2000s, selective intermolecular interactions based on hydrogen bonds and metal–molecule coordination enabled one to direct the assembling behaviors. Here, the concept of this directed assembly is opposite to that of the vdW-based self-assembly because the resulting architectures are purposefully tailored by programing intermolecular interaction. These efforts brought forth fruit in the on-surface syntheses of covalent bond networks. Particularly in the 2010s, on-surface covalent coupling was applied to graphene nanoribbons, where widths and edge structures can be precisely defined on the atomic scale. These works have the potential to bridge fundamental material nanoarchitectonics and functional device fabrication. In this paper, such a historical development of on-surface molecular nanoarchitectonics is reviewed, with the specific emphasis on the superiority of scanning tunneling microscopy. [ABSTRACT FROM AUTHOR]