Anthropogenic climate change has emerged as a critical environmental problem, prompting frequent investigations into its consequences for various ecological systems. Few studies, however, have explored the effect of climate change on ecological stability and the underlying mechanisms. We conduct a field experiment to assess the influence of warming and altered precipitation on the temporal stability of plant community biomass in an alpine grassland located on the Tibetan Plateau. We find that whereas precipitation alteration does not influence biomass temporal stability, warming lowers stability through reducing the degree of species asynchrony. Importantly, biomass temporal stability is not influenced by plant species diversity, but is largely determined by the temporal stability of dominant species and asynchronous population dynamics among the coexisting species. Our findings suggest that ongoing and future climate change may alter stability properties of ecological communities, potentially hindering their ability to provide ecosystem services for humanity.

The integration of two-dimensional (2D) van der Waals semiconductors into silicon electronics technology will require the production of large-scale, uniform, and highly crystalline films. We report a route for synthesizing wafer-scale single-crystalline 2H molybdenum ditelluride (MoTe2) semiconductors on an amorphous insulating substrate. In-plane 2D-epitaxy growth by tellurizing was triggered from a deliberately implanted single seed crystal. The resulting single-crystalline film completely covered a 2.5-centimeter wafer with excellent uniformity. The 2H MoTe2 2D single-crystalline film can use itself as a template for further rapid epitaxy in a vertical manner. Transistor arrays fabricated with the as-prepared 2H MoTe2 single crystals exhibited high electrical performance, with excellent uniformity and 100% device yield.

Among the Mo-and W-based two-dimensional (2D) transition metal dichalcogenides, MoTe 2 is particularly interesting for phase-engineering applications, because it has the smallest free energy difference between the semiconducting 2H phase and metallic 1T′ phase. In this work, we reveal that, under the proper circumstance, Mo and Te atoms can rearrange themselves to transform from a polycrystalline 1T′ phase into a single-crystalline 2H phase in a large scale. We manifest the mechanisms of the solid-to-solid transformation by conducting density functional theory calculations, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The phase transformation is well described by the time−temperature−transformation diagram. By optimizing the kinetic rates of nucleation and crystal growth, we have synthesized a single-crystalline 2H-MoTe 2 domain with a diameter of 2.34 mm, a centimeter-scale 2H-MoTe 2 thin film with a domain size up to several hundred micrometers, and a seamless 1T′−2H MoTe 2 coplanar homojunction. The 1T′−2H MoTe 2 homojunction provides an elegant solution for ohmic contact of 2D semiconductors. The controlled solid-to-solid phase transformation in 2D limit provides a new route to realize wafer-scale single-crystalline 2D semiconductor and coplanar heterostructure for 2D circuitry.

A high-performance NOT logic gate (inverter) was constructed by combining two identical n-channel metal-semiconductor field-effect transistors (MESFETs) made on a single CdS nanowire (NW). The inverter has a voltage gain as high as 83, which is the highest reported so far for inverters made on one-dimensional nanomaterials. The MESFETs used in the inverter circuit show excellent transistor performance, such as high on/off current ratio ( approximately 10(7)), low threshold voltage ( approximately -0.4 V), and low subthreshold swing ( approximately 60 mV/dec). With the assembly of three identical NW MESFETs, NOR and NAND gates have been constructed.

In this report, we find multilayered graphene, which has good transparency, conductivity and suitable work function, can be used as the anode for the organic light emitting device. Our device structure is Al/glass/multilayered graphene/V2O5/NPB/CBP:(ppy)2Ir(acac)/Bphen/Bphen:Cs2CO3/Sm/Au. The maximum luminance efficiency and maximum power efficiency reach 0.75 cd/A and 0.38 lm/W, respectively. We believe that by optimizing the hole density and uniforming the thickness of the multilayered graphene anode, the device efficiency can be remarkably increased in the future.

Two-dimensional (2D) layered semiconductors, with their ultimate atomic thickness, have shown promise to scale down transistors for modern integrated circuitry. However, the electrical contacts that connect these materials with external bulky metals are usually unsatisfactory, which limits the transistor performance. Recently, contacting 2D semiconductors using coplanar 2D conductors has shown promise in reducing the problematic high resistance contacts. However, many of these methods are not ideal for scaled production.Here, we report on the large-scale, spatially controlled chemical assembly of the integrated 2H-MoTe 2 field-effect transistors (FETs) with coplanar metallic 1T′-MoTe 2 contacts via phase engineered approaches. We demonstrate that the heterophase FETs exhibit ohmic contact behavior with low contact resistance, resulting from the coplanar seamless contact between 2H and 1T′ MoTe 2 confirmed by transmission electron microscopy characterizations. The average mobility of the heterophase FETs was measured to be as high as 23 cm 2 V −1 s −1 (comparable with those of exfoliated single crystals), due to the large 2H MoTe 2 single-crystalline domain (486±187 μm). By developing a patterned growth method, we realize the 1T′ MoTe 2 gated heterophase FET array whose components of channel, gate, and contacts are all 2D materials. Finally, we transfer the heterophase device array onto a flexible substrate and demonstrate the near-infrared photoresponse with high photoresponsivity (~1.02 A/W). Our study provides a basis for the large-scale application of phase-engineered coplanar MoTe 2 semiconductors-meter structure in advanced electronics and optoelectronics.

Flexible and transparent electronic and optoelectronic devices have attracted more and more research interest due to their potential applications in developing portable, wearable, low-cost, and implantable devices. We have fabricated and studied high-performance flexible and transparent CdSe nanobelt (NB)/graphene Schottky junction self-powered photovoltaic detectors for the first time. Under 633 nm light illumination, typical photosensitivity and responsivity of the devices are about 1.2 × 10(5) and 8.7 A W(-1), respectively. Under 3500 Hz switching frequency, the response and recovery times of them are about 70 and 137 μs, respectively, which, to the best of our knowledge, are the best reported values for nanomaterial based Schottky junction photodetectors up to date. The detailed properties of the photodetectors, such as the influences of incident light wavelength and light intensity on the external quantum efficiency and speed, are also investigated. Detailed discussions are made in order to understand the observed phenomena. Our work demonstrates that the self-powered flexible and transparent CdSe NB/graphene Schottky junction photovoltaic detectors have a bright application prospect.

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