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This work reveals the origin of PL evolution of InSe flake induced by weak and strong laser irradiation and provides a reliable experimental supplement to the photo oxidation study of InSe and opens up a new avenue to regulate the PL of InSe.

With excellent stability, flexibility, and piezoelectricity, poly(vinylidene fluoride) (PVDF) and its copolymer [P(VDF-TrFE)] have received much attention. However, the applications for its ferroelectricity still suffer the drawbacks of relative low remanent polarization (P r) and high coercive electric field (E c). In this work, P(VDF-TrFE) composite films were fabricated with the additive of organic perovskite ferroelectric MDABCO-NH4I3. Compared with pure P(VDF-TrFE), the P r increases from 7.17 to 12.7 μC cm−2, while E c decreases from 516 to 324 kV cm−1 as well as increased permittivity from 15.6 to 37.0. These may provide an alternative way for ferroelectric memory, sensors, and energy storage devices.

High-quality homogeneous junctions are of great significance for developing transition metal dichalcogenides (TMDs) based electronic and optoelectronic devices. Here, we demonstrate a lateral p-type/intrinsic/n-type (p-i-n) homojunction based multilayer WSe2 diode. The photodiode is formed through selective doping, more specifically by utilizing self-aligning surface plasma treatment at the contact regions, while keeping the WSe2 channel intrinsic. Electrical measurements of such a diode reveal an ideal rectifying behavior with a current on/off ratio as high as 1.2 × 106 and an ideality factor of 1.14. While operating in the photovoltaic mode, the diode presents an excellent photodetecting performance under 450 nm light illumination, including an open-circuit voltage of 340 mV, a responsivity of 0.1 A W-1, and a specific detectivity of 2.2 × 1013 Jones. Furthermore, benefiting from the lateral p-i-n configuration, the slow photoresponse dynamics including the photocarrier diffusion in undepleted regions and photocarrier trapping/detrapping due to dopants or doping process induced defect states are significantly suppressed. Consequently, a record-breaking response time of 264 ns and a 3 dB bandwidth of 1.9 MHz are realized, compared with the previously reported TMDs based photodetectors. The above-mentioned desirable properties, together with CMOS compatible processes, make this WSe2p-i-n junction diode promising for future applications in self-powered high-frequency weak signal photodetection.

Epidermal growth factor receptor variant III (EGFRvIII) is a mutant isoform of EGFR with a deletion of exons 2-7 making it insensitive to EGF stimulation and downstream signal constitutive activation. However, the mechanism underlying the stability of EGFRvIII remains unclear. Based on CRISPR-Cas9 library screening, we found that mucin1 (MUC1) is essential for EGFRvIII glioma cell survival and temozolomide (TMZ) resistance. We revealed that MUC1-C was upregulated in EGFRvIII-positive cells, where it enhanced the stability of EGFRvIII. Knockdown of MUC1-C increased the colocalization of EGFRvIII and lysosomes. Upregulation of MUC1 occurred in an NF-κB dependent manner, and inhibition of the NF-κB pathway could interrupt the EGFRvIII-MUC1 feedback loop by inhibiting MUC1-C. In a previous report, we identified AC1Q3QWB (AQB), a small molecule that could inhibit the phosphorylation of NF-κB. By screening the structural analogs of AQB, we obtained EPIC-1027, which could inhibit the NF-κB pathway more effectively. EPIC-1027 disrupted the EGFRvIII-MUC1-C positive feedback loop in vitro and in vivo, inhibited glioma progression, and promoted sensitization to TMZ. In conclusion, we revealed the pivotal role of MUC1-C in stabilizing EGFRvIII in glioblastoma (GBM) and identified a small molecule, EPIC-1027, with great potential in GBM treatment.

Hysteresis is a frequently observed phenomenon in the transfer characteristics of thin film transistors. Charge trapping/de-trapping processes of gate oxide and gate-channel interface are commonly known to be the origin of hysteresis and correlated to low frequency noise (LFN) properties of the devices. In this letter, a rapid four-point sweeping method (RFSM) is proposed to reveal the dependence of hysteresis, as well as the distribution of effective trap density on sweeping rate and gate bias range. Based on the RFSM, the hysteresis properties of four-layer MoS2 FETs are studied in detail. The experimental results demonstrate that the hysteresis and trap density at different frequencies and gate voltages, which could further roughly map the traps with different time constants and energy depths, can be obtained by the simple RFSM. Trap density estimated by RFSM shows a comparable range with that extracted from LFN, indicating that the traps inducing the hysteresis may also cause LFN.

The emergence of near-eye displays, such as head-mounted displays, is triggering a requirement for highly enhanced display resolution. High-resolution micro-displays with micro-organic light-emitting diodes (micro-OLEDs) can be a preferential candidate, owing to the mature industrialization of OLEDs along with the advantages of flexibility, light weight, and ease of processing. However, micro-OLEDs with pixel sizes down to micrometers are difficult to be achieved using conventional techniques such as fine metal mask evaporation and lithography. Here, a solution-processing approach to pattern organic semiconductors (OSCs) for micro-OLED arrays with the assistance of templated dewetting is demonstrated. Solvents containing organic functional materials are dewetted on the surface with hydrophobic/hydrophilic patterns to form ordered droplet arrays using dip-coating. Subsequently, patterned OSC films are produced by effectively controlling solvent evaporation. Micro-OLED arrays with a pixel size down to 1 µm are successfully fabricated by further deposition of emitting/electron transport layers and top electrodes. This approach can open an avenue for low-cost manufacturing of flexible and high-resolution micro-displays.

Numerous molecular ferroelectrics having excellent properties even comparable to inorganic ones, which usually contain heavy or toxic metals, have been developed recently. Hopefully, they can be used as substitutes for the well-known organic ferroelectric polymers (P(VDF-TrFE)) with huge coercive fields and poor spontaneous polarization for various applications. However, the bottleneck for practical applications, i.e., the preparation of high-quality thin films and high resolution device arrays with a desired crystallographic orientation for memory switching, still remains. In this study, large-area micro device arrays of molecular ferroelectrics with highly-crystalline or even single-crystalline films are intentionally self-assembled on electrodes or within electrode gaps using a solution processing technique, including the molecular ferroelectrics for which it is usually difficult to make thin films. The as-grown air-stable memory micro arrays with an optimum crystallographic orientation can exhibit excellent non-volatile memory performance with a smaller operation voltage of

Monolayer MoS2 is a direct bandgap semiconductor which is believed to be one of the most promising candidates for optoelectronic devices. Chemical vapor deposition (CVD) is the most popular method to synthesize monolayer MoS2 with a large area. However, many defects are always found in monolayer MoS2 grown by CVD, such as sulfur vacancies, which severely degrade the performance of devices. This work demonstrates a concise and effective method for direct growth of high quality monolayer MoS2 by using SiO2/Si substrates pretreated with sulfur vapor. The MoS2 monolayer obtained using this method shows about 20 times PL intensity enhancement and a much narrower PL peak width than that grown on untreated substrates. Detailed characterization studies reveal that MoS2 grown on sulfur vapor pretreated SiO2/Si substrates has a much lower density of sulfur vacancies. The synthesis of monolayer MoS2 with high optical quality and low defect concentration is critical for both fundamental physics studies and potential practical device applications in the atomically thin limit.

Two-dimensional heterojunctions exhibit many unique features in nanoelectronic and optoelectronic devices. However, heterojunction engineering requires a complicated alignment process and some defects are inevitably introduced during material preparation. In this work, a laser scanning technique is used to construct a lateral WSe2 p-n junction. The laser-scanned region shows p-type behavior, and the adjacent region is electrically n-doped with a proper gate voltage. The laser-oxidized product WOx is found to be responsible for this p-type doping. After laser scanning, WSe2 displays a change from ambipolar to unipolar p-type property. A significant photocurrent emerges at the p-n junction. Therefore, a self-powered WSe2 photodetector can be fabricated based on this junction, which presents a large photoswitching ratio of 106, a high photoresponsivity of 800 mA W-1, and a short photoresponse time with long-term stability and reproducibility. Therefore, this selective laser-doping method is prospective in future electronic applications.

Molecular ferroelectrics (MFs) have been proven to demonstrate excellent properties even comparable to those of inorganic counterparts usually with heavy metals. However, the validation of their device applications is still at the infant stage. The polycrystalline feature of conventionally obtained MF films, the patterning challenges for microelectronics and the brittleness of crystalline films significantly hinder their development for organic integrated circuits, as well as emerging flexible electronics. Here, a large-area flexible memory array is demonstrated of oriented molecular ferroelectric single crystals (MFSCs) with nearly saturated polarization. Highly-uniform MFSC arrays are prepared on large-scale substrates including Si wafers and flexible substrates using an asymmetric-wetting and microgroove-assisted coating (AWMAC) strategy. Resultant flexible memory arrays exhibit excellent nonvolatile memory properties with a low-operating voltage of5 V, i.e., nearly saturated ferroelectric polarization (6.5 µC cm

High-quality homogeneous junctions are of great significance for developing transition metal dichalcogenides (TMDs) based electronic and optoelectronic devices. Here, we demonstrate a lateral

Environmental influences are critical for the reliability of photoelectric devices, especially those using organic semiconductors. Among all the influence factors, the effect of relative humidity on the material's photoelectrical properties receives less attentions. To date, reported humidity effects are mostly related to the electrical properties. Their impact to the photoelectrical characteristics has rarely been investigated. In this work, we firstly report a detailed study on the dependency of material's photoelectrical properties on the relative humidity in photosensitive field effect transistors. It was found that both the amplitude and the decay time of the photocurrent indicated a profound dependency on the humidity. To further clarify the mechanism, experiments were carefully designed along with a simulation to recognize and to provide a detailed understanding on any possible influence factors in these processes. The results indicate a prominent co-existence of carrier-trapping and dielectric-polarization phenomena in the photoelectric device under the influences of humidity. Since the water molecules in the atmosphere are predominant, the observed variation in the photoelectrical properties can be explained.

Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality. Monolayer molybdenum disulfide (MoS2) and seed-assistant are the mostly selected 2D TMDC and growth strategy for such CVD processes, respectively. Though the advantages of seed catalysts in facilitating the nucleation, achieving higher yield and better repeatability, as well as their effects on the morphologies of as-grown MoS2 have been studied, the influence of seeding promoters on both optical and electrical properties of as-grown monolayer MoS2 is not known comprehensively, which is indeed critical for understanding fundamental physics and developing practical application of such emerging 2D semiconductors. In this report, we systematically investigated the effect of different seeding promoters on the properties of CVD-grown monolayer MoS2. It is found that different seed molecules lead to different impacts on the optical and electrical properties of as-grown monolayer MoS2. Among three different seed catalysts (perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS), copper phthalocyanine (CuPc), and crystal violet (CV)), PTAS performs better in obtaining large area monolayer MoS2 with good optical quality and high electrical mobility than the other two. Our work gives a guide for modifying the properties of as-grown monolayer MoS2 and other 2D transition metal dichalcogenides in seeding promoters-assisted synthesis process.

Most viscosity sensors, which are important in the health, automotive and food production industries, are currently based on mechanical or optical approaches. They are not compatible with emerging flexible and wearable electronics consisting of various lightweight integrated sensors with more compact architecture and lower cost. Here we demonstrate an organic device for sensing the viscosity of nonelectrolyte aqueous solutions which can work at low viscosities (0.9–10 mPa·s). The photoconductivity of devices involving semiconductor/water interfaces was found to obey Walden's rule, suggesting that viscosity could be measured by electrical means. This may be a promising approach for the design of viscosity sensors for portable and wearable applications. Keywords: Viscosity sensors, Organic photosensors, Glucose aqueous solution, Photoelectrochemical cells, Walden's rule

A new mercury coordination polymer was successfully prepared from HgCl2 and 5-methyltetrazole (Hmtz) and characterized by elemental analysis, thermal analysis, luminescence, theoretical calculation, powder X-ray diffraction and single-crystal X-ray diffraction. Complex 1 is a three-dimensional (3D) hybrid framework constructed from 1D double mercury halide chains and mtz−, and it has an unprecedented ‘AFUQOH’ topological network. Time-dependent density functional theory (TDDFT) calculations reveal that the mechanisms of the fluorescence emission of 1 are dominantly resulted from the metal-to-ligand charge transfer (MLCT) and ligand-to-metal charge transfer (MLCT). Impressively, acentric complex 1 displays not only second harmonic generation (SHG) response but also ferroelectric behaviors.

Heterostructures with built-in electric fields are crucial for charge separation and lateral photovoltaic effect in current position-sensitive detectors (PSDs), which have to be produced by combining semiconductors with metal or other semiconductors to form various vertical junctions (e.g. Schottky junctions) via complicated and high-cost manufacture processes. In the present work, it was found that vertical junctions can be directly written and patterned inside graphene oxide (GO) films with gradient C/O ratios by laser scribing due to the optical filter effect of the films and the formation of reduced GO (rGO) layers. Such junctions were verified to show the capability for high-precision position sensing on the micrometer scale, owing to the lateral photovoltaic effect. These self-powered laser-scribed PSDs can exhibit a small nonlinearity of

Monolayer MoS2 is a direct bandgap semiconductor which is believed to be one of the most promising candidates for optoelectronic devices. Chemical vapor deposition (CVD) is the most popular method to synthesize monolayer MoS2 with a large area. However, many defects are always found in monolayer MoS2 grown by CVD, such as sulfur vacancies, which severely degrade the performance of devices. This work demonstrates a concise and effective method for direct growth of high quality monolayer MoS2 by using SiO2/Si substrates pretreated with sulfur vapor. The MoS2 monolayer obtained using this method shows about 20 times PL intensity enhancement and a much narrower PL peak width than that grown on untreated substrates. Detailed characterization studies reveal that MoS2 grown on sulfur vapor pretreated SiO2/Si substrates has a much lower density of sulfur vacancies. The synthesis of monolayer MoS2 with high optical quality and low defect concentration is critical for both fundamental physics studies and potential practical device applications in the atomically thin limit.

Two-dimensional (2D) semiconductors, represented by 2D transition metal dichalcogenides (TMDs), exhibit rich valley physics due to strong spin-orbit/spin-valley coupling. The most common way to probe such 2D systems is to utilize optical methods, which can monitor light emissions from various excitonic states and further help in understanding the physics behind such phenomena. Therefore, 2D TMDs with good optical quality are in great demand. Here, we report a method to directly grow epitaxial WS2 and MoS2 monolayers on hexagonal boron nitride (hBN) flakes with a high yield and high optical quality; these monolayers show better intrinsic light emission features than exfoliated monolayers from natural crystals. For the first time, the valley Zeeman splitting of WS2 and MoS2 monolayers on hBN has been visualized and systematically investigated. This study paves a new way to produce high optical quality WS2 and MoS2 monolayers and to exploit their intrinsic properties in a multitude of applications. MOE (Min. of Education, S’pore)

Two-dimensional heterojunctions exhibit many unique features in nanoelectronic and optoelectronic devices. However, heterojunction engineering requires a complicated alignment process and some defects are inevitably introduced during material preparation. In this work, a laser scanning technique is used to construct a lateral WSe

In this investigation, we experimentally demonstrated a high-speed Gbps long-distance real-time visible light communication system based on non-return-to-zero on-off keying modulation by using a high-bandwidth Gallium nitride-based micro-LED with a modulation bandwidth of ∼230 MHz and a size of 40 μ m $ \times $ 40 μ m. The maximum real-time data rate obtained is up to 1.3 Gbps at a 3 m free-space transmission distance with a bit-error rate (BER) of 3.4 $ \times $ 10 –3 and 1 Gbps at a 10 m distance with a BER of 3.2 $ \times $ 10–3, both of which are underneath the forward error correction threshold of 3.8 $ \times $ 10–3 required for free-error operation. In addition, when the transmission distance is increased to 16 m in free space through reflecting the emission light beam by blue reflectors mounted on the wall, a data rate of 0.87 Gbps with a BER of 3.5 $ \times $ 10–3 is achieved successfully.

Microwave annealing (MWA) and furnace annealing are compared for their low thermal budget capability to improve the characteristics of ZnO-based thin-film transistors (TFTs). Both the ZnO channel and the Al2O3 gate dielectric are fabricated using atomic layer deposition. Using Si-wafer-susceptor assisted MWA with a substantial reduction of both annealing temperature and duration, significant improvements of the characteristics of the ZnO TFTs can be attained. A multi-step MWA process is found to further improve the characteristics of the TFTs. For the same microwave power and total duration, the field-effect mobility of the multi-step MWA TFT is 42% greater than that of the one-step MWA TFT with a similar sub-threshold swing. The multi-step MWA process can serve the purpose at temperatures as low as 220 °C.

Transition metal dichalcogenides (TMDCs) demonstrate great potential in numerous applications. However, these applications require a precise control of layer thickness at the atomic scale. In this work, we present an in-situ study of the self-limiting oxidation process in MoTe2 by ozone (O3) treatment. A precise layer-by-layer control of MoTe2 flakes can be achieved via multiple cycles of oxidation and wet etching. The thinned MoTe2 flakes exhibit comparable optical properties and film quality to the pristine exfoliated ones. Besides, an additional p-type doping is observed after O3 oxidation. Such a p-doping effect converts the device properties of MoTe2 from electron-dominated to hole-dominated ambipolar characteristics.

Photo-induced phase transitions (PIPTs) provide an ultrafast, energy-efficient way for precisely manipulating the topological properties of transition-metal ditellurides, and can be used to stabilize a topological phase in an otherwise semiconducting material. Using first-principles calculations, we demonstrate that the PIPT in monolayer MoTe$_2$ from the semiconducting 2H phase to the topological 1T$'$ phase can be triggered purely by electronic excitations that soften multiple lattice vibrational modes. These softenings, driven by a Peierls-like mechanism within the conduction bands, lead to structural symmetry breaking within sub-picosecond timescales, which is shorter than the timescale of a thermally driven phase transition. The transition is predicted to be triggered by photons with energies over $1.96$\,eV, with an associated excited carrier density of $3.4\times10^{14}$\,cm$^{-2}$, which enables a controllable phase transformation by varying the laser wavelength. Our results provide insight into the underlying physics of the phase transition in 2D transition-metal ditellurides, and show an ultrafast phase transition mechanism for manipulation of the topological properties of 2D systems., 3

Chemical vapor deposition synthesis of semiconducting transition metal dichalcogenides (TMDs) offers a new route to build next-generation semiconductor devices. But realization of continuous and uniform multilayer (ML) TMD films is still limited by their specific growth kinetics, such as the competition between surface and interfacial energy. In this work, a layer-by-layer vacuum stacking transfer method is applied to obtain uniform and non-destructive ML-MoS

In this study, we have realized controllable fabrication of gold nanopatterns on pristine monolayer graphene by using nanosphere lithography, in which polystyrene (PS) spheres are used as templates. With this method, periodically ordered triangular Au nanopatterns are uniformly formed on graphene surface. Micro-Raman spectroscopy shows that these sacrificial PS templates have no obvious effect on graphene surface structure while the subsequently formed Au nanopatterns are found to enhance Raman intensity of G and 2D bands by surface plasmon resonance. The compressive stress introduced in the metal deposition process leads to an obvious blue shift of 2D band. Besides, the metal-induced doping effect reduces the intensity ratio between 2D and G bands. This uniform arrangement of metal nanostructure is expected to grow other nanomaterials or used as Raman enhancement substrate in biomedicine, catalyzer and optics areas.

White light generated by mixing the red, green, and blue laser diodes (RGB LDs) for simultaneous high-speed underwater wireless optical communication (UWOC) and high-efficiency underwater solid-state lighting (SSL) was proposed and demonstrated experimentally for the first time. The allowable maximum real-time data transmission rates of 3.2 Gbps, 3.4 Gbps, and 3.1 Gbps for RGB LDs with corresponding BERs of 3.6 × 10−3, 3.5 × 10−3 and 3.7 × 10−3 were obtained at a 2.3 m underwater transmission distance using an on-off keying (OOK) modulation scheme, respectively. And the corresponding UWOC aggregate data rate of 9.7 Gbps was achieved based on RGB LDs-based wavelength-division multiplexing (WDM) UWOC. Moreover, UWOC and underwater SSL by using RGB LDs mixed white light were investigated at different scenarios over an underwater link of 2.3 m. The RGB LDs mixed white light-based UWOC system without optical diffusers yielded a maximum allowable data rate of 8.7 Gbps with Commission International de l’Eclairage coordinates (CIE) of (0.3154, 0.3354), a correlated color temperature of 6322 K, a color rendering index of 69.3 and a corresponding illuminance of 7084 lux. Furthermore, optical diffusers were employed to provide large-area underwater SSL. The LDs mixed white light-based UWOC system with line and circle optical diffusers implemented data rates of 5.9 Gbps and 6.6 Gbps with CIE coordinates of (0.3183, 0.3269) and (0.3298, 0.3390), respectively. This work suggests the potential of LDs for applications in high-efficiency underwater white-light SSL and high-speed UWOC.

In this report, an anomalous time-evolution of electrical current in organic thin-film transistors, OTFTs, is revealed by employing a specially tailored semiconductor composite channel. The composite is designed by controlling the density of carbon nanotubes dispersed in a host semiconducting polymer below electrical percolation. The current anomaly, which, to the best of our knowledge, has never been observed before, is directly correlated to strong many-body interactions instantaneously occurring in the system under investigation. In essence, two on-chain positively charged polarons are fused with an electrochemically generated negative hydroxyl ion, OH−, in the H2O/O2 redox reaction to form a trion. The trion, which is characteristic of the polymer, is intrinsically metastable and can dissociate to mobile polarons under the influence of electric field, temperature and/or light illumination. The rate of trion formation is almost three orders of magnitude higher than that of trion dissociation. The fast formation and slow dissociation of the trions is the cause responsible for the observed current anomaly. The metastable trion is, hence, of fundamental importance in the operation of OTFTs. Understanding the fundamentals pertaining to the anomalous phenomenon not only is crucial for design of more efficient devices but also can guide development of future, emerging applications of OTFTs.

As a representative two-dimensional semiconducting transition-metal dichalcogenide (TMD), the electronic structure in layered MoS2 is a collective result of quantum confinement, interlayer interaction, and crystal symmetry. A prominent energy splitting in the valence band gives rise to many intriguing electronic, optical, and magnetic phenomena. Despite numerous studies, an experimental determination of valence-band splitting in few-layer MoS2 is still lacking. Here, we show how the valence-band maximum (VBM) splits for one to five layers of MoS2. Interlayer coupling is found to contribute significantly to phonon energy but weakly to VBM splitting in bilayers, due to a small interlayer hopping energy for holes. Hence, spin-orbit coupling is still predominant in the splitting. A temperature-independent VBM splitting, known for single-layer MoS2, is, thus, observed for bilayers. However, a Bose-Einstein type of temperature dependence of VBM splitting prevails in three to five layers of MoS2. In such few-layer MoS2, interlayer coupling is enhanced with a reduced interlayer distance, but thermal expansion upon temperature increase tends to decouple adjacent layers and therefore decreases the splitting energy. Our findings that shed light on the distinctive behaviors about VBM splitting in layered MoS2 may apply to other hexagonal TMDs as well. They will also be helpful in extending our understanding of the TMD electronic structure for potential applications in electronics and optoelectronics.

Mitochondrial D2HGDH and L2HGDH catalyze the oxidation of D-2-HG and L-2-HG, respectively, into αKG. This contributes to cellular homeostasis in part by modulating the activity of αKG-dependent dioxygenases. Signals that control the expression/activity of D2HGDH/L2HGDH are presumed to broadly influence physiology and pathology. Using cell and mouse models, we discovered that MYC directly induces D2HGDH and L2HGDH transcription. Furthermore, in a manner suggestive of D2HGDH, L2HGDH, and αKG dependency, MYC activates TET enzymes and RNA demethylases, and promotes their nuclear localization. Consistent with these observations, in primary B cell lymphomas MYC expression positively correlated with enhancer hypomethylation and overexpression of lymphomagenic genes. Together, these data provide additional evidence for the role of mitochondria metabolism in influencing the epigenome and epitranscriptome, and imply that in specific contexts wild-type TET enzymes could demethylate and activate oncogenic enhancers.