High-performance and broadband photodetection of bicrystalline(GaN)_(1-x)(ZnO)_(x)solid solution nanowires via crystal defect engineering

Crystal defect engineering is widely used as an effective approach to regulate the optical and optoelectronic properties of semiconductor nanostructures.However,photogenerated electron-hole pair recombination centers caused by structural defects usually lead to the reduction of optoelectronic performance.In this work,a high-performance photodetector based on(GaN)_(1-x)(ZnO)_(x)solid solution nanowire with bicrystal structure is fabricated and it shows excellent photoresponse to ultraviolet and visible light.The highest responsivity of the photodetector is as high as 60,86 and 43 A/W under the irradiation of365 nm,532 nm and 650 nm,respectively.The corresponding response time is as fast as 170,320 and 160 ms.Such wide spectral responses can be attributed to various intermediate energy levels induced by the introduction of various structural defects and dopants in the solid solution nanowire.Moreover,the peculiar bicrystal boundary along the axial direction of the nanowire provides two parallel and fast transmission channels for photo-generated carriers,reducing the recombination of photo-generated carriers.Our findings provide a valued example using crystal defect engineering to broaden the photoresponse range and improve the photodetector performance and thus can be extended to other material systems for various optoelectronic applications.

The accelerating nanoscale Kirkendall effect in Co films–native oxide Si(100)system induced by high magnetic fields

The morphology evolution and magnetic properties of Co films–native oxide Si(100)were investigated at 873,973,and 1073 K in a high magnetic field of 11.5 T.Formation of Kirkendall voids in the Co films was found to cause morphology evolution due to the difference in diffusion flux of Co and Si atoms through the native oxide layer.The high magnetic fields had considerable effect on the morphology evolution by accelerating nanoscale Kirkendall effect.The diffusion mechanism in the presence of high magnetic fields was given to explain the increase of diffusion coefficient.The morphology evolution of Co films on native oxide Si(100)under high magnetic fields during annealing resulted in the magnetic properties variation.

Help, hope and hype： ethical considerations of human microbiome research and applications

Recent years have witnessed an unprecedented explosion of scientific knowledge and advances in human microbiome research due to the emerging high-throughput molecular technologies. The term human microbiome refers to the population of microorganisms, including bacteria, viruses, fungi and protozoan, and their genetic material that live on and inside the human organisms （skin, mucous membranes, intestinal tract, etc.） （Honey, 2008）. A search of the literature at PubMed for the term ＂microbiome＂ in the title and abstract illustrates the fast progression of microbiome science. From 2006 to 2010 there were just 304 papers that used the word microbiome in their title and/or abstract, whereas the number has increased to 11,128 from 2011 to 2017.

Magnetic-field-induced metal-insulator quantum phase transition in CaFeAsF near the quantum limit

The quantum limit, where only the lowest Landau level is occupied by electrons, can be achieved under a high magnetic field when the Landau level splitting is comparable with the Fermi energy. The rather small Fermi pockets and Fermi energy in CaFeAsF reported recently make this compound a good candidate for investigating the electrical transport near the quantum limit.Here, we report high-field experiments up to 65 T on a single-crystalline CaFeAsF, which shows a metal-insulator quantum phase transition tuned by the out-of-plane magnetic field. The obtained critical exponent zν through the finite-size scaling analysis is very close to 4/3. This transition is closely associated with the evolution of electronic states approaching the quantum limit.The resistivity behaviors as a function of field and temperature were evaluated based on Adams-Holstein theory(A-H theory).Moreover, the in-plane component of the field, which does not affect the transport behavior in the classical region, suppressed the magnetoresistance near the quantum limit.

In situ annealing effects on magnetic properties and variable-range hopping of iron-based ladder material BaFe2S3

All iron-based superconductors, regardless of their detailed crystal structure, share the same conductive Fe2X2 （X = As, P, Se, and S） layers as the crucial structural unit [1-8]. In the Fe2X2 layers, edge-shared FeX4 tetrahedra form a square lattice in quasi-two-dimensional （quasi-2D） planes. One may wonder what kind of properties will be manifested in the quasi-one-dimensional （quasi-1 D） counterparts exhibiting an identical coordination as the above-mentioned quasi-2D cases. Theoretical proposals on magnetic states and possible superconductivity have been reported in the recent five years [9-11]. Recently, a quasi-lD compound, BaFe：S3, with FeX4 tetrahedra extending along one direction, was studied and found to be superconductive at pressure around 11 GPa [ 12,13].

Crystal structure determination of nanolaminated Ti_(5)Al_(2)C_(3) by combined techniques of XRPD,TEM and ab initio calculations

Crystal structure of Ti_(5)Al_(2)C_(3)was determined by means of X-ray powder diffraction(XRPD),transmission electron microscopy(TEM)and ab initio calculations.In contrast to the already known P63/mmc space group that the MAX phases crystallize,it was demonstrated that the R3_m space group could better satisfy the experimental data.The lattice parameters are a=0.30564 nm,c=4.81846 nm in a hexagonal unit cell.

Seven facts and five initiatives for gut microbiome research

The gut microbiome has attracted increasing attention over the past 15 years.Along with the fast-growing body of research literature and media reports,the public's opinions on the gut microbiome have begun to appear polarized.Some believe that the gut microbiome is at the core of human health and is related to every single disease.To the opposite,some people question the scientific basis of gut microbiome studies and criticize that many of them are farfetched;there is even a joke spreading in the biomedical research field—"keeping gut microbiome in mind,no mechanism is hard to find".

Low-temperature and stable CO oxidation of Co_(3)O_(4)/TiO_(2) monolithic catalysts

Highly efficient Co_(3)O_(4)/TiO_(2) monolithic catalysts with enhanced stability were in-situ grown on Ti mesh for CO oxidation,which could completely oxidize CO at 120℃.The comprehensive catalytic performance is competitive to some noble metal catalysts and conventional Co_(3)O_(4) powder catalysts,which holds great potential toward industrial applications.Meanwhile,the in-situ synthesis strategy of Co_(3)O_(4)/TiO_(2) monolithic catalysts on flexible mesh substrate in this work can be extended to the development of a variety of oxide-based monolithic catalysts towards diverse catalysis applications.