Transition metal dichalcogenides (TMDs) are a category of promising two-dimensional (2D) materials for the optoelectronic devices, and their unique characteristics include tunable band gap, nondangling bonds as well as compatibility to large-scale fabrication, for instance, chemical vapor deposition (CVD). MoS 2 is one of the first TMDs that is well studied in the photodetection area widely. However, the low photoresponse restricts its applications in photodetectors unless the device is applied with ultrahigh source− drain voltage (V DS ) and gate voltage (V GS ). In this work, the photoresponse of a MoS 2 photodetector was improved by a chemical in situ doping method using gold chloride hydrate. The responsivity and specific detectivity were increased to 99.9 A/ W and 9.4 × 10 12 Jones under low V DS (0.1 V) and V GS (0 V), which are 14.6 times and 4.8 times higher than those of a pristine photodetector, respectively. The photoresponse enhancement results from chlorine n-type doping in CVD MoS 2 which reduces the trapping of photoinduced electrons and promotes the photogating effect. This novel doping strategy leads to great applications of high-performance MoS 2 photodetectors potentially and opens a new avenue to enhance photoresponse for other 2D materials.
Although
monovalent lithium has been successfully used as a coloring
ion in electrochromic applications, it still faces the challenges
of low safety, high cost, and limited reserves. Herein, we demonstrate
that the amorphous WO3 films intercalated with Al3+ ions could exhibit desired wide optical modulation (∼63.0%)
and high coloration efficiency (∼72.0 cm2 A–1, which is >100% higher than that with Li+ or Na+), benefiting from the three-electron redox properties
of aluminum. Due to the strong electrostatic force and large atomic
weight, the charge exchange processes for Al3+ ions are
limited only to the near-surface region and consequently bring about
enhanced electrochromic stability. Our findings provide in-depth insights
into the nature of electrochromism and also open up a new route toward scalable
electrochromic devices using sputtering techniques and earth-abundant
materials.
This paper addresses two questions concerning the relationship between state policies and environmental transformation in China in the past four decades. The first one deals with the promotion of agricultural productivity since the 1980s; the second, the water conservation measures as a response to the water crisis that peaked in the early 2000s. We had chosen Minqin County in northwestern China, one of the most fragile arid oasis systems in the world, as the study area. We found that the irrigated farmland in up and midstream areas had greatly expanded between the 1980s and the 2000s under the government policy of promoting commodity grain production. As a result, the runoff flowing into Minqin Oasis had reduced 80 % from the 1950s to early 2000s. Irrigated farmland in Minqin Oasis expanded 15.76 % from 1995 to 2000. In the 2000s, because of the changing policy discourse that has shifted from productivity to conservation, a new set of environmentally framed policies has restructured agricultural production in Minqin by 2005. These new policies included establishing a watershed-level water management system, promoting drought resistant crops, introducing water-saving irrigation measures, and forced reduction of irrigated farming acreage. These policies have produced positive results in terms of greater coverage of vegetation, rising ground water table, and reduction of evaporation. Nevertheless, new policies have also brought new challenges to both farmers and policy makers to keep the balance between poverty reduction and environmental sustainability in Minqin Oasis in the historically poor region in China's Northwest.
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