Designing hierarchical heterostructure to optimize the adsorption of hydrogen intermediate(H*)is impressive for hydrogen evolution reaction(HER)catalysis.Herein,we show that vertically mounting two-dimensional(2D)laye...Designing hierarchical heterostructure to optimize the adsorption of hydrogen intermediate(H*)is impressive for hydrogen evolution reaction(HER)catalysis.Herein,we show that vertically mounting two-dimensional(2D)layered molybdenum disulfide(MoS_(2))nanosheets on 2D nonlayered dimolybdenum carbide(Mo_(2)C)nanomeshes to form a hierarchical heterostructure largely accelerates the HER kinetics in acidic electrolyte due to the weakening adsorption strength of H*on 2D Mo_(2)C nanomeshes.Our hierarchical MoS2/Mo2C heterostructure therefore gives a decrease of overpotential for up to 500 mV at-10 mA·cm^(-2)and an almost 200-fold higher kinetics current density compared with the pristine Mo2C nanomeshes and maintains robust stability with a small drop of overpotential for only 16 mV upon 5,000 cycles.We further rationalize this finding by theoretical calculations and find an optimized adsorption free energy of H*,identifying that the MoS_(2)featuring strong H*desorption plays a key role in weakening the strong binding of Mo_(2)C with H*and therefore improves the intrinsic HER activity on active C sites of Mo_(2)C.This present finding shines the light on the rational design of heterostructured catalysts with synergistic geometry.展开更多
The integration of high-k dielectrics with two-dimensional(2D)semiconductors is a critical step towards high-performance nanoelectronics,which however remains challenging due to the high density of interface states an...The integration of high-k dielectrics with two-dimensional(2D)semiconductors is a critical step towards high-performance nanoelectronics,which however remains challenging due to the high density of interface states and the damage to the monolayer 2D semiconductors.In this study,we propose a selective hydrogenation strategy to improve the interface properties while the 2D semiconductors are not affected.Using the interface of monolayer molybdenum disulfide(MoS_(2))and silicon nitride as an example,we show substantially improved interface properties for electronic applications after the interfacial hydrogenation,as evidenced by reduced inhomogeneous charge redistribution,increased band offset,and nearly intact electronic properties of MoS_(2).Importantly,this hydrogenation process selectively occurs only at the silicon nitride surface and is compatible with the current semiconductor fabrication process.We further show that this strategy is general and applicable to other interfaces between high-k dielectrics and 2D semiconductors such as hafnium dioxide(HfO_(2))on the monolayer MoS_(2).Our results demonstrate a simple yet viable way to improve the integration of high-k dielectrics on a broad range of 2D transition metal disulfide semiconductors,shedding light on practical electronic and optoelectronic applications.展开更多
Molybdenum disulfide(MoS_(2)),one of transition metal dichalcogenides,is a promising semiconductor material for electronic or optoelectronic devices due to its favorably electronic properties.However,in metal-oxide se...Molybdenum disulfide(MoS_(2)),one of transition metal dichalcogenides,is a promising semiconductor material for electronic or optoelectronic devices due to its favorably electronic properties.However,in metal-oxide semiconductor field-effect transistor(MOSFET)structures using MoS_(2),electrical performances such as mobility and subthreshold swing are suppressed by the interface trap density between the channel and dielectric layers.Moreover,the electrical stability of such structures is compromised due to interface traps and that can be analyzed such as current hysteresis and transient characteristics.Here,we demonstrate MoS_(2) heterojunction field-effect transistors(HFET)by applying MoS_(2)/p^(+)-Si heterojunctions and achieve high performance characteristics,including a mobility of 636.19 cm^(2)/(V∙s),a subthreshold swing of 67.4 mV/dec,minimal hysteresis of 0.05 V,and minimized transient characteristics.However,the HFET devices with varying the channel length demonstrated degradation of electrical performance with increasing the overlap area of the channel and dielectric layers.These results regarding MoS_(2)/p^(+)-Si HFETs resulted in the structural optimization of high-performance electronic devices for practical applications.展开更多
Recently,the layered transition metal dichalcogenide 1T′-MoTe2 has generated considerable interest due to their superconducting and non-trivial topological properties.Here,we present a systematic study on 1T′-MoTe2 ...Recently,the layered transition metal dichalcogenide 1T′-MoTe2 has generated considerable interest due to their superconducting and non-trivial topological properties.Here,we present a systematic study on 1T′-MoTe2 single-crystal and exfoliated thin-flakes by means of electrical transport,scanning tunnelling microscope(STM)measurements and band structure calculations.For a bulk sample,it exhibits large magneto-resistance(MR)and Shubnikov–de Hass oscillations inρxx and a series of Hall plateaus inρxy at low temperatures.Meanwhile,the MoTe2 thin films were intensively investigated with thickness dependence.For samples,without encapsulation,an apparent transition from the intrinsic metallic to insulating state is observed by reducing thickness.In such thin films,we also observed a suppression of the MR and weak anti-localization(WAL)effects.We attributed these effects to disorders originated from the extrinsic surface chemical reaction,which is consistent with the density functional theory(DFT)calculations and in-situ STM results.In contrast to samples without encapsulated protection,we discovered an interesting superconducting transition for those samples with hexagonal Boron Nitride(h-BN)film protection.Our results indicate that the metallic or superconducting behavior is its intrinsic state,and the insulating behavior is likely caused by surface oxidation in few layer 1T’-MoTe2 flakes.展开更多
基金Supported by the National Natural Science Foundation of China(11991063,62004207,61725505,62104118)the Shanghai Science and Technology Committee(2019SHZDZX01,19XD1404100,20YF1455900,20ZR1474000)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB43010200)the Youth Innovation Promotion Association CAS(2018276)。
基金The authors thank the supports from the Fundamental Research Funds for the Central Universities(No.40120631)the Zhejiang Provincial Natural Science Foundation(Nos.LQ22B060003 and LY20E020004)+1 种基金the Fundamental Research Funds for the Provincial Universities of Zhejiang(No.2020YQ005)the Research Foundation of Talented Scholars of Zhejiang A&F University(No.2020FR069).
文摘Designing hierarchical heterostructure to optimize the adsorption of hydrogen intermediate(H*)is impressive for hydrogen evolution reaction(HER)catalysis.Herein,we show that vertically mounting two-dimensional(2D)layered molybdenum disulfide(MoS_(2))nanosheets on 2D nonlayered dimolybdenum carbide(Mo_(2)C)nanomeshes to form a hierarchical heterostructure largely accelerates the HER kinetics in acidic electrolyte due to the weakening adsorption strength of H*on 2D Mo_(2)C nanomeshes.Our hierarchical MoS2/Mo2C heterostructure therefore gives a decrease of overpotential for up to 500 mV at-10 mA·cm^(-2)and an almost 200-fold higher kinetics current density compared with the pristine Mo2C nanomeshes and maintains robust stability with a small drop of overpotential for only 16 mV upon 5,000 cycles.We further rationalize this finding by theoretical calculations and find an optimized adsorption free energy of H*,identifying that the MoS_(2)featuring strong H*desorption plays a key role in weakening the strong binding of Mo_(2)C with H*and therefore improves the intrinsic HER activity on active C sites of Mo_(2)C.This present finding shines the light on the rational design of heterostructured catalysts with synergistic geometry.
基金M.Y.acknowledges the funding support(Nos:1-BE47 and ZE2F)from The Hong Kong Polytechnic University.
文摘The integration of high-k dielectrics with two-dimensional(2D)semiconductors is a critical step towards high-performance nanoelectronics,which however remains challenging due to the high density of interface states and the damage to the monolayer 2D semiconductors.In this study,we propose a selective hydrogenation strategy to improve the interface properties while the 2D semiconductors are not affected.Using the interface of monolayer molybdenum disulfide(MoS_(2))and silicon nitride as an example,we show substantially improved interface properties for electronic applications after the interfacial hydrogenation,as evidenced by reduced inhomogeneous charge redistribution,increased band offset,and nearly intact electronic properties of MoS_(2).Importantly,this hydrogenation process selectively occurs only at the silicon nitride surface and is compatible with the current semiconductor fabrication process.We further show that this strategy is general and applicable to other interfaces between high-k dielectrics and 2D semiconductors such as hafnium dioxide(HfO_(2))on the monolayer MoS_(2).Our results demonstrate a simple yet viable way to improve the integration of high-k dielectrics on a broad range of 2D transition metal disulfide semiconductors,shedding light on practical electronic and optoelectronic applications.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP)(No.NRF-2020R1A4A4078674).
文摘Molybdenum disulfide(MoS_(2)),one of transition metal dichalcogenides,is a promising semiconductor material for electronic or optoelectronic devices due to its favorably electronic properties.However,in metal-oxide semiconductor field-effect transistor(MOSFET)structures using MoS_(2),electrical performances such as mobility and subthreshold swing are suppressed by the interface trap density between the channel and dielectric layers.Moreover,the electrical stability of such structures is compromised due to interface traps and that can be analyzed such as current hysteresis and transient characteristics.Here,we demonstrate MoS_(2) heterojunction field-effect transistors(HFET)by applying MoS_(2)/p^(+)-Si heterojunctions and achieve high performance characteristics,including a mobility of 636.19 cm^(2)/(V∙s),a subthreshold swing of 67.4 mV/dec,minimal hysteresis of 0.05 V,and minimized transient characteristics.However,the HFET devices with varying the channel length demonstrated degradation of electrical performance with increasing the overlap area of the channel and dielectric layers.These results regarding MoS_(2)/p^(+)-Si HFETs resulted in the structural optimization of high-performance electronic devices for practical applications.
基金The work was supported by the Guangdong Innovative and Entrepreneurial Research Team Program,China(Grant No.2016ZT06D348)the National Natural Science Foundation of China(Grant No.11874193)the Shenzhen Fundamental Subject Research Program,China(Grant No.JCYJ20170817110751776).K.D.W.acknowledges support from the National Natural Science Foundation of China(Grant No.11574128).X.D.acknowledges support from NSF under award DMR-1808491.
文摘Recently,the layered transition metal dichalcogenide 1T′-MoTe2 has generated considerable interest due to their superconducting and non-trivial topological properties.Here,we present a systematic study on 1T′-MoTe2 single-crystal and exfoliated thin-flakes by means of electrical transport,scanning tunnelling microscope(STM)measurements and band structure calculations.For a bulk sample,it exhibits large magneto-resistance(MR)and Shubnikov–de Hass oscillations inρxx and a series of Hall plateaus inρxy at low temperatures.Meanwhile,the MoTe2 thin films were intensively investigated with thickness dependence.For samples,without encapsulation,an apparent transition from the intrinsic metallic to insulating state is observed by reducing thickness.In such thin films,we also observed a suppression of the MR and weak anti-localization(WAL)effects.We attributed these effects to disorders originated from the extrinsic surface chemical reaction,which is consistent with the density functional theory(DFT)calculations and in-situ STM results.In contrast to samples without encapsulated protection,we discovered an interesting superconducting transition for those samples with hexagonal Boron Nitride(h-BN)film protection.Our results indicate that the metallic or superconducting behavior is its intrinsic state,and the insulating behavior is likely caused by surface oxidation in few layer 1T’-MoTe2 flakes.
基金This work was supported by grants from the National Basic Research Program of China (No.2012CB922001),the National Natural Science Foundation of China(Nos.21571166,61076040,51271173,and 21071136),the Specialized Research Fund for the Doctoral Program of Higher Education of China (No.2012011111006),the Nature Science Foundation of Anhui Province (No.J2014AKZR0059),and the Fundamental Research Funds for the Central Universities (Nos.JZ2015HGXJ0182,JZ2014HGBZ0063,and WK6030000019).
