Bioinspired Multifunctional Organic Transistors Based on Natural Chlorophyll/Organic Semiconductors

Inspired by the photosynthesis process of natural plants, multifunctional transistors based on natural biomaterial chlorophyll and organic semiconductors (OSCs) are reported. Functions as photodetectors (PDs) and light-stimulated synaptic transistors (LSSTs) can be switched by gate voltage. As PDs, the devices exhibit ultrahigh photoresponsivity up to 2 × 10⁶ A W⁻¹, detectivity of 6 × 10¹⁵ Jones, and I_photo/I_dark ratio of 2.7 × 10⁶, which make them among the best reported organic PDs. As LSSTs, important synaptic functions similar to biological synapses are demonstrated, together with a dynamic learning and forgetting process and image-processing function. Significantly, benefiting from the ultrahigh photosensitivity of chlorophyll, the lowest operating voltage and energy consumption of the LSSTs can be 10⁻⁵ V and 0.25 fJ, respectively. The devices also exhibit high flexibility and long-term air stability. This work provides a new guide for developing organic electronics based on natural biomaterials.     

Electrochemical performance in seawater and microstructural evolution of friction stir welded joints of dissimilar AA1050 and AZ91D

This paper presents the electrochemical performance and microstructural evolution of friction stir welded joint of dissimilar AA1050 and AZ91D in seawater, for potential applications in the transportation industry. The corrosion behavior of the dissimilar weld was compared to the corrosion behavior of the parent materials, and similar welds of each alloy. The experiments were successfully conducted with an H13 hot-working tool steel in butt-joint configuration. The results revealed the presence of intercalated microstructure in the dissimilar weld and homogenous microstructures in the similar welds. The corrosion resistance properties of the parent materials and similar welds were higher than that of the dissimilar weld sample. The dissimilar weld has a current density of 3.83×10⁻⁵ A/cm² and corrosion rate of 9.99×10⁻⁴ mm/year; and is most susceptible to corrosion, due to the galvanic coupling between the dissimilar alloys and intermetallic compounds. The similar weld of AA1050 has a current density of 1.99×10⁻⁷ A/cm² and corrosion rate of 1.44×10⁻³ mm/year, while the similar weld of AZ91D has a current density of 8.58×10⁻⁶ A/cm² and corrosion rate of 1.13×10⁻¹ mm/year.     

Modifying the morphology and structure of graphene oxide provides high-performance LiFePO4/C/rGO composite cathode materials

In this study we synthesized LiFePO₄/carbon/reduced graphene oxide (LFP/C/rGO) composite cathode materials using a method involving sol–gel processing, spray-drying, and calcination. To improve the electrochemical performance of LFP/C, we tested graphene oxides (GOs) of various morphologies as conductive additives, including pristine GO, three-dimensional GO, and hydrothermal porous GO (HTGO). Among our samples, the cathode material prepared through spray-drying with the addition of 1 wt% of HTGO (denoted SP-LFP/C/1%rHTGO) displayed the best electrochemical performance; its discharge capacities at 0.1C, 1C, 5C, and 10C were 160.5, 151.8, 138.8, and 130.3 mA h g⁻¹, respectively. From measurements of its long-term cycling performance, the discharge capacity in the first cycle and the capacity retention after 30 cycles at 0.1C were 160.2 mA h g⁻¹ and 99.6%, respectively; at 10C, these values were 132.2 mA h g⁻¹ and 91.8%, respectively. The electronic conductivity of SP-LFP/C/1%rHTGO (6.58 × 10⁻⁵ S cm⁻¹) was higher than that of the pristine LFP/C (9.24 × 10⁻⁶ S cm⁻¹). The Li⁺ ion diffusivities (D_Li⁺) of the SP-LFP/C/1%HTGO cathode, measured using AC impedance (3.91 × 10⁻¹³ cm² s⁻¹) and cyclic voltammetry (6.66 × 10⁻¹⁰ cm² s⁻¹ for discharge), were superior to those of the LFP/C cathode (9.31 × 10⁻¹⁵ cm² s⁻¹ and 1.79 × 10⁻¹⁰ cm² s⁻¹ for discharge, respectively). Galvanostatic intermittent titration revealed that the value of D_Li⁺ was located in a reasonable range from 1 × 10⁻¹⁰ to 1 × 10⁻¹⁷ cm² s⁻¹; its value dropped to its lowest point when the state of charge was close to 50%. Thus, the use of spray-drying and the addition of conductive HTGO (having a 3D wrinkled morphology and interconnected pore structure) can enhance the electronic conductivity and Li⁺ ion diffusivity of LFP/C cathode materials, thereby improving the electrochemical performance significantly.     

A High‐Performance Optical Memory Array Based on Inhomogeneity of Organic Semiconductors

Organic optical memory devices keep attracting intensive interests for diverse optoelectronic applications including optical sensors and memories. Here, flexible nonvolatile optical memory devices are developed based on the bis[1]benzothieno[2,3‐d;2′,3′‐d′]naphtho[2,3‐b;6,7‐b′]dithiophene (BBTNDT) organic field‐effect transistors with charge trapping centers induced by the inhomogeneity (nanosprouts) of the organic thin film. The devices exhibit average mobility as high as 7.7 cm² V^?1 s^?1, photoresponsivity of 433 A W^?1, and long retention time for more than 6 h with a current ratio larger than 10⁶. Compared with the standard floating gate memory transistors, the BBTNDT devices can reduce the fabrication complexity, cost, and time. Based on the reasonable performance of the single device on a rigid substrate, the optical memory transistor is further scaled up to a 16 × 16 active matrix array on a flexible substrate with operating voltage less than 3 V, and it is used to map out 2D optical images. The findings reveal the potentials of utilizing [1]benzothieno[3,2‐b][1]benzothiophene (BTBT) derivatives as organic semiconductors for high‐performance optical memory transistors with a facile structure. A detailed study on the charge trapping mechanism in the derivatives of BTBT materials is also provided, which is closely related to the nanosprouts formed inside the organic active layer.     

Metal‐Ion‐Modified Black Phosphorus with Enhanced Stability and Transistor Performance

Black phosphorus (BP), a burgeoning elemental 2D semiconductor, has aroused increasing scientific and technological interest, especially as a channel material in field‐effect transistors (FETs). However, the intrinsic instability of BP causes practical concern and the transistor performance must also be improved. Here, the use of metal‐ion modification to enhance both the stability and transistor performance of BP sheets is described. Ag⁺ spontaneously adsorbed on the BP surface via cation–π interactions passivates the lone‐pair electrons of P thereby rendering BP more stable in air. Consequently, the Ag⁺‐modified BP FET shows greatly enhanced hole mobility from 796 to 1666 cm² V^?1 s^?1 and ON/OFF ratio from 5.9 × 10⁴ to 2.6 × 10⁶. The mechanisms pertaining to the enhanced stability and transistor performance are discussed and the strategy can be extended to other metal ions such as Fe³⁺, Mg²⁺, and Hg²⁺. Such stable and high‐performance BP transistors are crucial to electronic and optoelectronic devices. The stability and semiconducting properties of BP sheets can be enhanced tremendously by this novel strategy.     

Preparation and characterisation of Au/InGaP/GaAs Schottky barriers for radiation damage investigation

High quality Au/InGaP Schottky diodes have been prepared as efficient test structures for a study of the radiation hardness of InGaP as space solar cell material. A detailed characterisation of the metal–semiconductor barriers obtained on both n (free carrier concentration ranging from 3×l0¹⁵ to 1.2×l0¹⁸ cm⁻³) and p-type (3.5×10¹⁷ cm⁻³) InGaP epitaxial layers lattice matched to GaAs substrate has been performed using current–voltage, capacitance–voltage and internal photoemission techniques. Excellent electrical properties were found for low doped (ideality factor of 1.05–1.06, rectification ratio of about 10¹⁰ at 0.7 V, reverse current lower than 1×10⁻¹² A at −2 V) as well as heavily doped samples (rectification ratios of about 10⁵ at 0.6 V). The barrier height values calculated by the different techniques were compared and discussed. Deep level transient spectroscopy (DLTS) spectra obtained on unirradiated samples did not show detectable deep levels with the exception of the heaviest doped sample showing a weak peak associated to the DX centre. After electron irradiation at 9 MeV with doses ranging from 5×l0¹³ to 1.5×10¹⁵ e cm⁻² the samples exhibited a broad dominant peak (activation energy in the 0.90–0.93 eV range) whose intensity increased linearly with the absorbed dose. The broadening of the peak and the observed increase of the corresponding trap concentration with the doping level suggest that this peak could be associated to complexes due to the interaction of primary defects, created by high irradiation energy, with each others and with the shallow impurities.     

Hydrogen-Doping-Induced Metal-Like Ultrahigh Free-Carrier Concentration in Metal-Oxide Material for Giant and Tunable Plasmon Resonance

The practical utilization of plasmon-based technology relies on the ability to find high-performance plasmonic materials other than noble metals. A key scientific challenge is to significantly increase the intrinsically low concentration of free carriers in metal-oxide materials. Here, a novel electron–proton co-doping strategy is developed to achieve uniform hydrogen doping in metal-oxide MoO₃ at mild conditions, which creates a metal-like ultrahigh free-carrier concentration approaching that of noble metals (10²¹ cm⁻³ in H_1.68MoO₃ versus 10²² cm⁻³ in Au/Ag). This bestows giant and tunable plasmonic resonances in the visible region to this originally semiconductive material. Using ultrafast spectroscopy characterizations and first-principle simulations, the formation of a quasi-metallic energy band structure that leads to long-lived and strong plasmonic field is revealed. As verified by the surface-enhanced Raman spectra (SERS) of rhodamine 6G molecules on H_xMoO₃, the SERS enhancement factor reaches as high as 1.1 × 10⁷ with a detection limit at concentration as low as 1 × 10⁻⁹ mol L⁻¹, representing the best among the hitherto reported non-metal systems. The findings not only provide a set of metal-like semiconductor materials with merits of low cost, tunable electronic structure, and plasmonic resonance, but also a general strategy to induce tunable ultrahigh free-carrier concentration in non-metal systems.     

Centimeter-Sized Single Crystals of Dion-Jacobson Phase Lead-Free Double Perovskite for Efficient X-ray Detection

2D Dion–Jacobson (DJ) phase hybrid perovskites have shown great promise in the photoelectronic field owing to their outstanding optoelectronic performance and superior structural rigidity. However, DJ phase lead-free double perovskites are still a virgin land with direct X-ray detection. Herein, we have designed and synthesized a new DJ phase lead-free layered double perovskite of (HIS)₂AgSbBr₈ ( 1 , HIS²⁺ = histammonium). Centimeter-sized (18 × 10 × 5 mm³) single crystals of 1 are successfully grown via the temperature cooling technique, exhibiting remarkable semiconductive characteristics such as a high resistivity (2.2 × 10¹¹ Ω cm), a low trap state density (3.56 × 10¹⁰ cm⁻³), and a large mobility-lifetime product (1.72 × 10⁻³ cm² V⁻¹). Strikingly, its single-crystal-based X-ray detector shows a high sensitivity of 223 µC Gy⁻¹_air cm⁻² under 33.3 V mm⁻¹, a low detection limit (84.2 nGy_airs⁻¹) and superior anti-fatigue. As far as we know, we firstly demonstrates the potential of 2D DJ phase lead-free hybrid double perovskite in X-ray detection, showing excellent photoelectric response and operational stability. This work will pave a promising pathway to the innovative application of hybrid perovskites for eco-friendly and efficient X-ray detection.     

Electronic-Grade High-Quality Perovskite Single Crystals by a Steady Self-Supply Solution Growth for High-Performance X-ray Detectors

High-quality perovskite single crystals with large size are highly desirable for the fundamental research and high energy detection application. Here, a simple and convenient solution method, featuring continuous-mass transport process (CMTP) by a steady self-supply way, is shown to keep the growth of semiconductor single crystals continuously stable at a constant growth rate until an expected crystal size is achieved. A significantly reduced full width at half-maximum (36 arcsec) of the (400) plane from the X-ray rocking curve indicates a low angular dislocation of 6.8 × 10⁶ cm⁻² and hence a higher crystalline quality for the CH₃NH₃PbI₃(MAPbI₃) single crystals grown by CMTP as compared to the conventional inverse temperature crystallization (ITC) method. Furthermore, the CMTP-based single crystals have lower trap density, reduced by nearly 200% to 4.5 × 10⁹ cm⁻³, higher mobility increased by 187% to 150.2 cm² V⁻¹ s⁻¹, and higher mobility–lifetime product increased by around 450% to 1.6 × 10⁻³ cm² V⁻¹, as compared with the ITC-grown reference sample. The high performance of the CMTP-based MAPbI₃ X-ray detector is comparable to that of a traditional high-quality CdZnTe device, indicating the CMTP method as being a cost-efficient strategy for high-quality electronic-grade semiconductor single crystals.     

A cooled,intense polarized hydrogen atomic beam for the ETH polarized ion source

A slow (35 K) atomic beam with I⩾10¹⁷ atoms s⁻¹ and n_H∼2×10¹² atoms cm⁻³ has been developed. On the ETH polarized ion source, DC intensities of 0.4 mA for positive and 16 μA for negative ions have been observed.     

Resilient composite of silicone and foamed tin as a new material for electrical and thermal contacts

Silicone-infiltrated tin foam containing 14 volume % metal is a new composite material that is resilient up to a compressive stress of 2 MPa and a strain of 13%. Its volume electrical resistivity is 5 × 10⁻⁴ω cm and remains below 1 × 10⁻³ω cm up to 1700 compressive loading cycles (0.075 MPa). Its contact resistivity (with copper) decreases with pressure and levels off at 0.22 ω cm² at a pressure of 0.07 MPa. Beyond 1000 compressive loading cycles (0.08 MPa), the contact resistivity rises, reaching 0.48 ω cm² at 1700 cycles. The thermal expansion coefficient is 215 × 10⁻⁶°C⁻¹ at 45°C, compared with a value of 282 × 10⁻⁶°C⁻¹ for silicone. This composite is attractive as a material for electrical and thermal contacts in electronic packages. Compared with silicone-infiltrated tin foam, silicone-infiltrated tin-lead foam exhibits a lower volume electrical resistivity, a lower contact resistivity (with copper) and a higher fatigue resistance, but it is resilient only up to a compressive stress of 0.4 MPa and a strain of 0.8%. The bonding between silicone and tin is stronger than that between silicone and tin-lead.     

Honeycomb RhI3 Flakes with High Environmental Stability for Optoelectronics

The emerging 2D layered transition metal trihalides (MX₃) have attracted extremely high interest given their exceptional structural and physical properties. Continuing to extend the library of 2D MX₃ is essential for exploring new physical phenomena and enabling new functionality. Herein, the optical and electrical properties and the photodetection behavior of atomically thin RhI₃ flakes exfoliated from bulk crystals are reported. This compound exhibits superior air and thermal stability, as well as thickness-dependent bandgap from 1.1 (18L) to 1.4 eV (2L). Field-effect transistors based on the few-layer RhI₃ flakes display n-type semiconducting behavior with competitive mobility of 2.5 cm² V⁻¹ s⁻¹ and ON/OFF current ratio of 4 × 10⁴. Importantly, the outstanding responsivity of 11.5 A W⁻¹ and high specific detectivity of 2 × 10¹⁰ Jones are recorded from the RhI₃ photodetectors under 980 nm illumination at room temperature in air. These findings indicate a variety of potential applications of atomically thin RhI₃ flakes in future 2D-material-based electronic and optoelectronic devices.     

SdH oscillations in the contact resistance of bismuth nanowires

Measurements of the magnetoresistance of 30-nm diameter bismuth nanowires where the trigonal crystalline axis is parallel to the wire axis have been carried out for various angles between the nanowires axis and the magnetic field including the longitudinal and transverse orientation for magnetic fields up to 14 T. At high magnetic fields, as the carrier's cyclotron radius becomes smaller than the wire diameter, we observe Shubnikov-de Haas resonances from the quantization into Landau levels in the wire interior. The wires display a nearly isotropic short period of 0.025 T⁻¹, consistent with a heavy carrier concentration of 1.5×10¹⁸ cm⁻³, a five-fold increase from the bulk value of 3.0×10¹⁷ cm⁻³. Dresselhaus's theory of quantum confinement shows that Bi wires should change from semimetallic to semiconducting behavior for diameter smaller than a critical diameter of 50 nm, which is difficult to reconcile with the present measurements. Our results also discussed in terms of a surface-induced surface hole concentration that circumvent the semimetal-to-semiconductor transition, a model that has been introduced to explain transport measurements on thin Bi films.     

Novel Tunnel‐Contact‐Controlled IGZO Thin‐Film Transistors with High Tolerance to Geometrical Variability

Thin insulating layers are used to modulate a depletion region at the source of a thin‐film transistor. Bottom contact, staggered‐electrode indium gallium zinc oxide transistors with a 3 nm Al₂O₃ layer between the semiconductor and Ni source/drain contacts, show behaviors typical of source‐gated transistors (SGTs): low saturation voltage (V_{D_SAT} ≈ 3 V), change in V_{D_SAT} with a gate voltage of only 0.12 V V^?1, and flat saturated output characteristics (small dependence of drain current on drain voltage). The transistors show high tolerance to geometry: the saturated current changes only 0.15× for 2–50 µm channels and 2× for 9‐45 µm source‐gate overlaps. A higher than expected (5×) increase in drain current for a 30 K change in temperature, similar to Schottky‐contact SGTs, underlines a more complex device operation than previously theorized. Optimization for increasing intrinsic gain and reducing temperature effects is discussed. These devices complete the portfolio of contact‐controlled transistors, comprising devices with Schottky contacts, bulk barrier, or heterojunctions, and now, tunneling insulating layers. The findings should also apply to nanowire transistors, leading to new low‐power, robust design approaches as large‐scale fabrication techniques with sub‐nanometer control mature.     

Proton conductive membranes based on silicotungstic acid/silica and polybenzimidazole

Membranes formed by polybenzimidazole and silicotungstic acid supported on silica have been prepared. The membranes were characterized in order to evaluate their proton conduction, mechanical stability and structural characteristics. Silica produced a beneficial effect on proton conduction of the membranes. The membranes with 50 wt.% of SiWA–SiO₂/PBI was mechanically stable and gave proton conductivity of 1.2×10⁻³ S cm⁻¹ at 160°C and 100% relative humidity. All the materials prepared had amorphous structure.     

An evaluation of (100) sulfur doped inp for use as a first crystal in an X-ray double-crystal diffractometer

X-ray double-crystal rocking curves for (100) oriented slices were studied. Although the dislocation density for a gradient freeze slice (2 × 10³cm⁻²) was significantly lower than that of a liquid encapsulated Czochralski slice (5 × 10⁴cm⁻²), both samples were found to have 12–14 arcsec rocking curve linewidths. These results indicate that the linewidth is not primarily dependent on the dislocation density.     

General Spatial Confinement Recrystallization Method for Rapid Preparation of Thickness-Controllable and Uniform Organic Semiconductor Single Crystals

Organic semiconductor single crystals (OSSCs) are ideal materials for studying the intrinsic properties of organic semiconductors (OSCs) and constructing high-performance organic field-effect transistors (OFETs). However, there is no general method to rapidly prepare thickness-controllable and uniform single crystals for various OSCs. Here, inspired by the recrystallization (a spontaneous morphological instability phenomenon) of polycrystalline films, a spatial confinement recrystallization (SCR) method is developed to rapidly (even at several second timescales) grow thickness-controllable and uniform OSSCs in a well-controlled way by applying longitudinal pressure to tailor the growth direction of grains in OSCs polycrystalline films. The relationship between growth parameters including the growth time, temperature, longitudinal pressure, and thickness is comprehensively investigated. Remarkably, this method is applicable for various OSCs including insoluble and soluble small molecules and polymers, and can realize the high-quality crystal array growth. The corresponding 50 dinaphtho[2,3-b:2″,3″-f]thieno[3,2-b]thiophene (DNTT) single crystals coplanar OFETs prepared by the same batch have the mobility of 4.1 ± 0.4 cm² V⁻¹ s⁻¹, showing excellent uniformity. The overall performance of the method is superior to the reported methods in term of growth rate, generality, thickness controllability, and uniformity, indicating its broad application prospects in organic electronic and optoelectronic devices.     

Carbon layers formed on steel and Ti alloys after ion implantation of C+ at very high doses

Ion implantation is a useful technique to tailor surface properties of steel and Ti alloys. In particular, very high dose C⁺ implantation (in the range of 10¹⁸ ions cm⁻²) offers the possibility of forming carbon layers without a sharp interface with the substrate material. In this study, ion implantation of carbon doses up to 8×10¹⁸ ions cm⁻² has been performed on 440C martensitic stainless steel and Ti6Al4V substrates under similar conditions and tribological and surface analysis results have been compared. Surface hardening occurred for all ion implantation conditions up to doses of 10¹⁸ ions cm⁻²1, 2, 3. Higher doses resulted in a different behaviour for both materials. The stainless steel showed a softening while a twofold hardness increase was maintained in the Ti alloy. Nevertheless, at the higher implanted dose a decrease in hardness was also observed in the Ti alloy. Small area XPS analyses were performed to evaluate the chemical states after ion implantation and establish a relationship with the observed surface hardening. Depth profile XPS analyses showed that for a dose of 4×10¹⁸ ions cm⁻² a carbon layer (with concentration over 85% at. C) was formed in the near surface region for both materials.     

Transmission electron microscopy of Li+ implanted Al films

Aluminium films implanted with 30 keV lithium ions of doses from 2.2 × 10¹⁶ to 1 × 10¹⁷ ions cm^?2 were studied by transmission electron microscopy. Samples implanted with 6 × 10¹⁶ and 1 × 10¹⁷ ions cm^?2 showed the presence of the Al-Li phase, while no change was observed in specimens implanted with 2.2 × 10¹⁶ ions cm^?. Microdiffraction patterns obtained from different areas of an aluminium film implanted with 2.0 × 10¹⁷ Li⁺ ions cm^?2 at 35 keV, revealed the presence of a stable Al-Li phase along with a metastable phase. Furthermore, on annealing the implanted samples at 200°C for 20 min an increase in ‘d’ values was noticed when compared with non-annealed specimens. However the annealed samples showed a very small lattice mismatch between the metastable phase and the Al matrix, thus indicating the presence of a metastable Al₃Li phase, responsible for hardening in binary Al-Li alloy.     

Ion implantation of microcrystalline silicon for low process temperature top gate thin film transistors

Ion implantation of phosphorus was used to dope amorphous and microcrystalline silicon with the aim of achieving a low-temperature, self-aligned process for forming n⁺ contacts to top-gate thin-film transistors. Amorphous and microcrystalline films made with both RF glow discharge and hot-wire chemical vapor deposition were implanted. The effect of the dose, energy and implantation temperature and subsequent annealing at increasing temperatures on the dark conductivity, activation energy and photoconductivity were studied. Lowering the energy (15 keV) while increasing the dose (10¹⁵ cm⁻²) and the implantation temperature (300°C) resulted in the highest after anneal (300°C) dark conductivity for both hot-wire (0.3 Ω⁻¹ cm⁻¹) and RF (0.2 Ω⁻¹ cm⁻¹) microcrystalline films.