Directional growth of ultralong nanowires (NWs) is significant for practical application of large-scale optoelectronic integration. Here, we demonstrate the controlled growth of in-plane directional perovskite CsPbBr NWs, induced by graphoepitaxial effect on annealed M-plane sapphire substrates. The wires have a diameter of several hundred nanometers, with lengths up to several millimeters. Microstructure characterization shows that CsPbBr NWs are high-quality single crystals, with smooth surfaces and well-defined cross section. The NWs have very strong band-edge photoluminescence (PL) with a long PL lifetime of ∼25 ns and can realize high-quality optical waveguides. Photodetectors constructed on these individual NWs exhibit excellent photoresponse with an ultrahigh responsivity of 4400 A/W and a very fast response speed of 252 μs. This work presents an important step toward scalable growth of high-quality perovskite NWs, which will provide promising opportunities in constructing integrated nanophotonic and optoelectronic systems.

Atomically thin PtSe 2 films have attracted extensive research interests for potential applications in high-speed electronics, spintronics and photodetectors. Obtaining high quality, single crystalline thin films with large size is critical. Here we report the first successful layer-by-layer growth of high quality PtSe 2 films by molecular beam † The authors declare no competing financial interest. 1 arXiv:1703.04279v2 [cond-mat.mtrl-sci] 15 Mar 2017 epitaxy. Atomically thin films from 1 ML to 22 ML have been grown and characterized by low-energy electron diffraction, Raman spectroscopy and X-ray photoemission spectroscopy. Moreover, a systematic thickness dependent study of the electronic structure is revealed by angle-resolved photoemission spectroscopy (ARPES), and helical spin texture is revealed by spin-ARPES. Our work provides new opportunities for growing large size single crystalline films for investigating the physical properties and potential applications of PtSe 2 . KeywordsPtSe 2 , Molecular beam epitaxy (MBE), Raman, ARPES, Transition metal dichalcogenide (TMDC) Layered transition metal dichalcogenides (TMDCs) have attracted extensive interests for applications in electronics, optoelectronics and valleytronics due to the strong spin-orbit coupling, sizable band gap and tunability of the electronic structure by quantum confinement effect. [1][2][3][4] In the past decade, this has been witnessed by the significant efforts conducted on the atomically thin MoS 2 film. 5-7 However, its low mobility has limited applications, for inbstance, in high speed electronics. 8,9 Finding thin films of other TMDC with better properties is highly desirable. PtSe 2 has emerged as an interesting compound that belongs to TMDC.Although the bulk crystal is a semimetal, 10,11 monolayer (ML) platinum diselenide (PtSe 2 ) has been revealed to be a semiconductor with a band gap of ≈ 1.2 eV. 12 Importantly, the charge-carrier mobility of PtSe 2 has been predicted among the highest in TMDCs 9 and has been experimentally shown to be comparable to black phosphorene 13 yet with the advantage of much improved stability. 14 This makes PtSe 2 a promising candidate for high-speed electronics. Moreover, the hidden helical spin texture with spin-layer locking in monolayer PtSe 2 has been recently revealed, 15 and such spin physics induced by a local Rashba effect has great potential for electric field tunable spintronic devices. 16 In addition, remarkable performance

No abstract

Methylammonium lead halide perovskites have attracted enormous attentions due to their superior optical and electronic properties. However, the photodetection at near-infrared telecommunication wavelengths is hardly achievable because of their wide bandgaps. Here, this study demonstrates, for the first time, novel perovskite-erbium silicate nanosheet hybrid photodetectors with remarkable spectral response at ≈1.54 µm. Under the near-infrared light illumination, the erbium silicate nanosheets can give strong upconversion luminescence, which will be well confined in their cavities and then be efficiently coupled into and simultaneously excite the adjacent perovskite to realize photodetection. These devices own prominent responsivity and external quantum efficiency as high as previously reported microscale silicon-based subbandgap photodetectors. More importantly, the photoresponse speed (≈900 µs) is faster by five orders than the ever reported hot electron silicon-based photodetectors at telecommunication wavelengths. The realization of perovskite-based telecommunication band photodetectors will open new chances for applications in advanced integrated photonics devices and systems.

Organometal halide perovskites are new light-harvesting materials for lightweight and flexible optoelectronic devices due to their excellent optoelectronic properties and low-temperature process capability. However, the preparation of high-quality perovskite films on flexible substrates has still been a great challenge to date. Here, a novel vapor-solution method is developed to achieve uniform and pinhole-free organometal halide perovskite films on flexible indium tin oxide/poly(ethylene terephthalate) substrates. Based on the as-prepared high-quality perovskite thin films, high-performance flexible photodetectors (PDs) are constructed, which display a nR value of 81 A W at a low working voltage of 1 V, three orders higher than that of previously reported flexible perovskite thin-film PDs. In addition, these flexible PDs exhibit excellent flexural stability and durability under various bending situations with their optoelectronic performance well retained. This breakthrough on the growth of high-quality perovskite thin films opens up a new avenue to develop high-performance flexible optoelectronic devices.

Field-effect transistors with ionic-liquid gating (ILG) have been widely employed and have led to numerous intriguing phenomena in the last decade, due to the associated excellent carrier-density tunability. However, the role of the electrochemical effect during ILG has become a heavily debated topic recently. Herein, using ILG, a field-induced insulator-to-metal transition is achieved in WO thin films with the emergence of structural transformations of the whole films. The subsequent secondary-ion mass spectrometry study provides solid evidence that electrochemically driven hydrogen evolution dominates the discovered electrical and structural transformation through surface absorption and bulk intercalation.

It is of great interest to elucidate underlying mechanisms to maintain stability of anaerobic digestion, an important process in waste treatment. By operating triplicate anaerobic digesters continuously for two years, we found that microbial community composition shifted over time despite stable process performance. Using an association network analysis to evaluate microbial interactions, we detected a clear successional pattern, which exhibited increasing modularity but decreasing connectivity among microbial populations. Phylogenetic diversity was the most important factor associated with network topology, showing positive correlations with modularity but negative correlations with network complexity, suggesting induced niche differentiation over time. Positive, but not negative, correlation strength was significantly related (p < 0.05) to phylogeny. Furthermore, among populations exhibiting consistent positive correlations across networks, close phylogenetic linkages were evident (e.g. Clostridiales organisms). Clostridiales organisms were also identified as keystone populations in the networks (i.e., they had large effects on other species), suggestive of an important role in maintaining process stability. We conclude that microbial interaction dynamics of anaerobic digesters evolves over time during stable process performance.

The main purpose of this study is to identify the impact of green banking activities on green financing and banks’ environmental performance. It also identifies the mediating effect of green financing on the relationship between green banking activities and environmental performance of private commercial banks (PCBs) in Bangladesh. Besides, this study also examines the major challenges and benefits of green banking development in an emerging economy like Bangladesh. The convenience sampling technique was used to collect primary data from bankers of PCBs in Bangladesh, and a final sample size of 352 was recorded. To assess the relationship among the study variables, the Structural Equation Modelling (SEM) approach was employed. The empirical results revealed that green banking activities exhibit a significantly positive effect on banks’ environmental performance and sources of green financing, and that sources of green financing significantly influence banks’ environmental performance. Additionally, it was observed that green financing mediates the association between green banking activities and banks’ environmental performance. Furthermore, the study identified customers’ insufficient awareness towards green banking, high investment costs, technical obstacles, lack of capable and competent staff in appraising green credits/loans, and difficulties and complexity in assessing green projects as major challenges affecting the development of green banking in Bangladesh. Moreover, the study also discovered that increasing banks’ competitiveness, reducing long-term costs and expenses, providing online banking facilities, improving customers’ goodwill, and reducing carbon footprints are the key benefits of green banking development, as it helps in the achievement of the sustainable economic development of the country. Therefore, major theoretical and managerial policy implications are further discussed with study limitations and future research directions.