High-performance asymmetric electrodes photodiode based on Sb/WSe2 heterostructure

Two-dimensional (2D) van der Waals (vdWs) metal-semiconductor heterostructures with atomically sharp interface and matched work functions have recently attracted great attention due to their unique electronic and optoelectronic properties. Here we report the vapor phase epitaxial growth of large-scale vertical Sb/WSe2 metal-semiconductor vdWs heterostructures with uniform stacking orientation. Compared with the growth on S1O2/S1 substrate, the thick ness of Sb nan osheet on WSe2 can be reduced effectively to mono layer. We con struct Sb-WSe2-Au asymmetric electrodes photodiode based on the Sb/WSe2 heterostructures. Electrical transport measurements indicate that the photodiode show obvious rectifying effect. Optoelectronic characterizations show prominent photoresponse with a high photoresposivity of 364 mA/W, a fast response time of less than 8 ms, a large open-circuit voltage of 0.27 V and a maximum electrical power output of 0.11 nW. The direct growth of high-quality metal-semiconductor vdWs heterostructures may open up new realms in 2D functional electronics and optoelectronics.

Tunable Schottky barrier width and enormously enhanced photoresponsivity in Sb doped SnS2 monolayer

Doping, which is the intentional introducti on of impurities into a material, can improve the metal-semiconductor interface by reducing Schottky barrier width. Here, we prese nt high-quality two-dime nsional SnS2 nano sheets with well-controlled Sb dopi ng concen tration via direct vapor growth approach and following micromechanical cleavage process. X-ray photoelectro n spectroscopy (XPS) measureme nt dem on strates that Sb contents of the doped samples are approximately 0.22%, 0.34% and 1.21%, respectively, and doping in duces the upward shift of the Fermi level with respect to the pristi ne SnS2. Tran smissio n electro n microscopy (TEM) characterizatio n exhibits that Sb-doped SnS2 nano sheets have a high-quality hexagonal symmetry structure and Sb element is uniformly distributed in the nano sheets. The phototra nsistors based on the Sb-doped SnS2 mono layers show n-type behavior with high mobility which is one order of magn itude higher than that of pristi ne SnS2 phototra nsistors. The photorespo nsivity and exter nal quantum efficiency (EQE) of Sb-S nS2 mono layers phototra nsistors are approximately three orders of magnitude higher than that of pristine SnS2 phototransistor. The results suggest that the method of reducing Shottky barrier width to achieve high mobility and photoresp on sivity is effective, and Sb-doped SnS2 mono layer has significant potential in future nanoelectronic and optoelectronic applications.

Increased winter-spring precipitation from the last glaciation to the Holocene inferred from a δ^(13)C_(org) record from Yili Basin(Xinjiang, NW China)

The nature and dynamics of climate change in central Asia since the late Pleistocene are controversial. Moreover,most of the published studies focus mainly on the evolution of moisture conditions, and there have been few attempts to address changes in seasonality. In this study, records of δ^(13)C_(org), TOC, TN, C/N and grain size were obtained from lacustrine sediments at Yili Basin, Xinjiang, NW China. Our aim was to reconstruct the trend in seasonality of precipitation from the last glaciation to the Holocene. The organic matter content of the sediments is derived predominantly from terrestrial plants. The δ^(13)C_(org)values vary from-19.4‰ to-24.8‰, indicating that the vegetation was dominated by C_3 plants. Winter-spring precipitation is identified as the factor determining the relative proportions of C_3 and C_4 plants in the region. A negative trend in δ^(13)C_(org)corresponding to an increase in the relative abundance of C_3 plants indicate a trend of increasing winter-spring precipitation from the last glaciation to the Holocene. The increased incidence of wintertime storms in the interior of Asia is suggested to result in the increase of winterspring precipitation in the Holocene.