Abstract:The discovery of monolayer superconductors bears consequences for both fundamental physics and device applications. Currently, the growth of superconducting monolayers can only occur under ultrahigh vacuum and on specific lattice-matched or dangling bond-free substrates, to minimize environment- and substrate-induced disorders/defects. Such severe growth requirements limit the exploration of novel two-dimensional superconductivity and related nanodevices. Here we demonstrate the experimental realization of sup… Show more
“…As shown in Figure a, the mixture of CuO and NaCl was used as copper source. The addition of salt can decrease the high melting point of metal oxides, increase their vapor pressure by forming oxychlorides during reaction and therefore have been used to synthesize a great variety of TMDCs . In our pursuit of synthesizing high quality, thin Cu 9 S 5 nanoflakes, NaCl also played an important role as only sparse nanoparticles can be grown without it, see Figure b and Figure S1 in the Supporting Information.…”
P‐n junctions based on two dimensional (2D) van der Waals (vdW) heterostructure are one of the most promising alternatives in next‐generation electronics and optoelectronics. By choosing different 2D transition metal dichalcogenides (TMDCs), the p‐n junctions have tailored energy band alignments and exhibit superior performance as photodetectors. The p‐n diodes working at reverse bias commonly have high detectivity due to suppressed dark current but suffer from low responsivity resulting from small quantum efficiency. Greater build‐in electric field in the depletion layer can improve the quantum efficiency by reducing recombination of charge carriers. Herein, Cu9S5, a novel p‐type semiconductor with direct bandgap and high optical absorption coefficient, is synthesized by salt‐assisted chemical vapor deposition (CVD) method. The high density of holes in Cu9S5 endows the constructed p‐n junction, Cu9S5/MoS2, with strong build‐in electric field according to Anderson heterojunction model. Consequently, the Cu9S5/MoS2 p‐n heterojunction has low dark current at reverse bias and high photoresponse under illumination due to the efficient charge separation. The Cu9S5/MoS2 photodetector exhibits good photodetectivity of 1.6 × 1012 Jones and photoresponsivity of 76 A W−1 under illumination. This study demonstrates Cu9S5 as a promising p‐type semiconductor for high‐performance p‐n heterojunction diodes.
“…As shown in Figure a, the mixture of CuO and NaCl was used as copper source. The addition of salt can decrease the high melting point of metal oxides, increase their vapor pressure by forming oxychlorides during reaction and therefore have been used to synthesize a great variety of TMDCs . In our pursuit of synthesizing high quality, thin Cu 9 S 5 nanoflakes, NaCl also played an important role as only sparse nanoparticles can be grown without it, see Figure b and Figure S1 in the Supporting Information.…”
P‐n junctions based on two dimensional (2D) van der Waals (vdW) heterostructure are one of the most promising alternatives in next‐generation electronics and optoelectronics. By choosing different 2D transition metal dichalcogenides (TMDCs), the p‐n junctions have tailored energy band alignments and exhibit superior performance as photodetectors. The p‐n diodes working at reverse bias commonly have high detectivity due to suppressed dark current but suffer from low responsivity resulting from small quantum efficiency. Greater build‐in electric field in the depletion layer can improve the quantum efficiency by reducing recombination of charge carriers. Herein, Cu9S5, a novel p‐type semiconductor with direct bandgap and high optical absorption coefficient, is synthesized by salt‐assisted chemical vapor deposition (CVD) method. The high density of holes in Cu9S5 endows the constructed p‐n junction, Cu9S5/MoS2, with strong build‐in electric field according to Anderson heterojunction model. Consequently, the Cu9S5/MoS2 p‐n heterojunction has low dark current at reverse bias and high photoresponse under illumination due to the efficient charge separation. The Cu9S5/MoS2 photodetector exhibits good photodetectivity of 1.6 × 1012 Jones and photoresponsivity of 76 A W−1 under illumination. This study demonstrates Cu9S5 as a promising p‐type semiconductor for high‐performance p‐n heterojunction diodes.
“…CVD involves chemical reactions of gaseous reactants on a heated substrate surface [54,55]. The CVD approach has been used successfully in synthesizing 1T-VS 2 [56,57], 1T-VSe 2 [58,59], 2H-NbS 2 [60], 3R-NbS 2 [60], 2H-NbSe 2 [61], 1T-TaS 2 [62,63], 1T-TiSe 2 [64], and so on. Contamination-free and high crystalline quality samples with potential for scaling-up are the great advantages of the CVD method [65].…”
Abstract:Recently, two-dimensional (2D) charge density wave (CDW) materials have attracted extensive interest due to potential applications as high performance functional nanomaterials. As other 2D materials, 2D CDW materials are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into layers of single unit cell thickness. Although bulk CDW materials have been studied for decades, recent developments in nanoscale characterization and device fabrication have opened up new opportunities allowing applications such as oscillators, electrodes in supercapacitors, energy storage and conversion, sensors and spinelectronic devices. In this review, we first outline the synthesis techniques of 2D CDW materials including mechanical exfoliation, liquid exfoliation, chemical vapor transport (CVT), chemical vapor deposition (CVD), molecular beam epitaxy (MBE) and electrochemical exfoliation. Then, the characterization procedure of the 2D CDW materials such as temperature-dependent Raman spectroscopy, temperature-dependent resistivity, magnetic susceptibility and scanning tunneling microscopy (STM) are reviewed. Finally, applications of 2D CDW materials are reviewed.
“…Liu and co‐workers accomplished the synthesis of monolayer NbSe 2 domains with the edge length of ≈0.2 mm on SiO 2 /Si, through a salt‐assisted APCVD method (Figure a), with the oxidized niobium powder (NbO x ) ( x ≤ 2.5) as the precursor . A schematic model for the reaction chamber was shown in Figure b.…”
Section: Preparation Methods Of 2d Mtmdcsmentioning
confidence: 99%
“…c) HRADF‐STEM image of the hexagonal NbSe 2 lattice. Reproduced with permission . Copyright 2017, Nature Publishing Group.…”
Section: Preparation Methods Of 2d Mtmdcsmentioning
confidence: 99%
“…As for the optimization of the precursors, alkali metal halides (e.g., NaCl, KI) were confirmed as growth promoters for the growth of 2D MTMDC nanosheets by decreasing the melting points of metal precursors (transition metals or their oxides) . Typically, monolayer NbSe 2 crystals with large domain sizes (submillimeter) on the SiO 2 /Si substrate were synthesized through a salt‐assisted CVD route . The monolayer NbSe 2 presented a lower superconducting transition critical temperature T c = 1.0 K than that of the multilayer samples.…”
2D metallic transition metal dichalcogenides (MTMDCs) have become the focus of intense research in many fields due to their novel physical and chemical properties (e.g., charge‐density wave order, unconventional superconductivity, and magnetism), as well as their extraordinary performance in advanced nanoelectronics and energy‐related fields. Herein, the preparation methods of 2D MTMDCs, such as chemical exfoliation via alkali metal intercalation, colloidal synthesis, and chemical vapor deposition (CVD), and their applications in electrocatalytic hydrogen evolution reactions (HERs) are comprehensively discussed. In particular, the first part focuses on various synthetic routes of 2D MTMDC nanosheets with different thicknesses and domain sizes, as well as the crucial factors in the corresponding synthetic process. In addition, the different growth mechanisms via the CVD processes caused by common insulating substrates (e.g., SiO2/Si, mica), unique conducing substrates (e.g., Au foil), and novel porous substrates (e.g., nanoporous gold) are also compared. In the second part, the excellent electrocatalytic performances of 2D MTMDC nanosheets in HER are also demonstrated by combining density functional theory (DFT) calculations and experimental results. Finally, challenges regarding the preparation of MTMDC nanosheets and probable routes for further improving the HER performance are also highlighted, and the future research directions are also proposed.
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