Research Advance on Carbon Storage of Artificial Grassland in China

As an essential part of the grassland ecological system,study on the carbon storage has great significances to the carbon reduction in grassland ecological system.The carbon storage in biomass,carbon storage in soil and soil respiration are summarized in this paper to provide scientific reference for the evaluation of carbon storage in artificial grassland.

Superconducting nanostrip single photon detectors fabricated of aluminum thin-films

We systematically investigated the detection performance of Al nanostrips for single photons at various wavelengths.The Al films were deposited using magnetron sputtering,and the sophisticated nanostructures and morphology of the deposited films were revealed through high-resolution transmission electron microscopy.The fabricated Al meander nanostrips,with a thickness of 4.2 nm and a width of 178 nm,exhibited a superconducting transition temperature of 2.4 K and a critical current of approximately 5μA at 0.85 K.While the Al nanostrips demonstrated a saturated internal quantum efficiency for 405-nm photons,the internal detection efficiency exhibited an exponential dependence on bias current without any saturation tendency for 1550-nm photons.This behavior can be attributed to the relatively large diffusion coefficient and coherence length of the Al films.By further narrowing the nanostrip width,the Al-SNSPDs remain capable of effectively detecting single telecom photons to facilitate practical applications.

Magnetron co-sputtering synthesis and nanoindentation studies of nanocrystalline(TiZrHf)_(x)(NbTa)_(1–x)high-entropy alloy thin films

Refractory high-entropy alloys(HEAs)possess many useful properties such as high strength and high-temperature stability.So far,most studies on refractory HEAs have been limited to a few well-known compositions and on their coarse-grain bulk forms.Here we fabricate nanocrystalline(TiZrHf)_(x)(NbTa)_(1−x)HEA thin films with a large range of compositions(x=0.07–0.90)by the direct current(DC)magnetron co-sputtering technique and measure their mechanical properties using the nanoindentation method.All the as-deposited HEA thin films show a solid-solution body-centered cubic(bcc)structure.As the compositional ratio(x)increases,the elastic modulus decreases from 153 to 123 GPa,following the trend of the rule of mixture.As x increases,the hardness first decreases from 6.5 GPa(x=0.07)to the lowest value(4.6 GPa,x=0.48)and then increases to the highest value(7.1 GPa,x=0.90),showing a concave trend.The change in hardness might be attributed to the combinational influence caused by the atomic size and modulus effects,as well as the texture effect.The authors also propose a few open questions for future studies on this and related HEA systems.

Geometric origin of intrinsic dark counts in superconducting nanowire single-photon detectors

The dark count is one of the key physical issues for superconducting nanowire single-photon detectors(SNSPDs)that limits various applications for optical quantum information and classical optics.When the bias current approaches the switching current of SNSPDs,the dark count is actually dominated by the intrinsic dark counts(iDCs).However,the origin of iDCs and its relation to constrictions remains unclear for practical SNSPDs.We herein systematically characterize the iDCs of the SNSPDs with and without artificial geometric constrictions by applying the differential readout method.For these devices with constrictions,we have observed distinct Gaussian distributions in the temporal distribution of iDCs,in which the time difference between the distributions is consistent with the geometric distance between constrictions,and the rates of iDCs produced by each constriction are in good agreement with constrictions'widths.With respect to practical SNSPDs,surprisingly,we also observe several Gaussian distributions in the temporal domain and it shows no significant dependence on the devices’sizes,demonstrating that the iDCs of SNSPDs are mainly dominated by a few specific constrictions.