保证服务质量的Q_0S路由(Quality of service Routing)是网络中解决Q_0S问题的一项关键技术。本文讨论了Q_0S路由中的基本问题。度量参数选择问题、寻路问题是Q_0S路由中的几个主要研究内容。本文围绕这两个方面,介绍了Q_0S路由中的主...保证服务质量的Q_0S路由(Quality of service Routing)是网络中解决Q_0S问题的一项关键技术。本文讨论了Q_0S路由中的基本问题。度量参数选择问题、寻路问题是Q_0S路由中的几个主要研究内容。本文围绕这两个方面,介绍了Q_0S路由中的主要问题及相关的解决办法。展开更多
The morphology and structural stability of metal/2D semic on ductor interfaces strongly affect the performa nee of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces h...The morphology and structural stability of metal/2D semic on ductor interfaces strongly affect the performa nee of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces has not been well explored particularly at atomic resolution. In this work, we study the structural evoluti on of Au nan oparticles (NPs) on few-layer MoS2 by high resol utio n transmissi on electro n microscopy (HRTEM) an d quan titative high-angle annular dark field seanning TEM. It is found that in the transition of Au from nan oparticles to den drites, a dynamically epitaxial align ment betwee n Au and MoS2 lattices is formed, and Moirc patter ns can be directly observed in HRTEM images due to the mismatch between Au and M0S2 lattices. This epitaxial alignment can occur in ambient conditions, and can also be accelerated by the irradiation of high-energy electron beam. In situ observation clearly reveals the rotation of Au NPs, the atom migration inside Au NPs, and the transfer of Au atoms between neighboring Au NPs, finally leading to the formation of epitaxially aligned Au dendrites on M0S2. The structural evoluti on of metal/2D semico nductor in terfaces at atomic scale can provide valuable information for the design and fabricatio n of the metal/2D semicon ductorn ano-devices with desired physical and chemical performa nces.展开更多
The solid lubricant M0S_(2) demonstrates excellent lubricating properties,but it spontaneously oxidizes and absorbs moisture in air,and thus results in poor wear resistance and short wear-life.In this study,the additi...The solid lubricant M0S_(2) demonstrates excellent lubricating properties,but it spontaneously oxidizes and absorbs moisture in air,and thus results in poor wear resistance and short wear-life.In this study,the additive g-C_(3)N_(4)(CN)was successfully combined with M0S_(2) via hydrothermal synthesis as a solid lubricant for the first time.Meanwhile,a low friction coefficient(COF,y=0.031)and ultra-long wear-life of CN/M0S_(2) compared to pure M0S_(2) in air were demonstrated.The functional groups and good crystallinity of the lubricant material were characterized via Fourier transform infrared(FTIR)spectroscopy and X-ray diffraction(XRD).The formed valence states in CN/M0S_(2) were analyzed via X-ray photoelectron spectroscopy(XPS).The characterized results of the scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HRTEM)show the morphology and interior crystal phase structure of CN/M0S_(2).From the cross-section analysis,the presence of iron oxide nanoparticles lubricating film is synergistic with CN/M0S_(2) film during the friction process,resulting in its ultra-long wear-life.In particular,the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed.展开更多
Developing non-precious metal catalysts with high activity and stability for electrochemical hydrogen evolution reaction(HER)is of great significance in both scie nee and tech no logy.In this work,N-doped CMK-3,which ...Developing non-precious metal catalysts with high activity and stability for electrochemical hydrogen evolution reaction(HER)is of great significance in both scie nee and tech no logy.In this work,N-doped CMK-3,which was prepared with a casting method using SBA-15 as thehard template and ammonia as the nitrogen source,has been utilized to hold MoS2 and restrict its growth to form MoS2@N-CMK-3 composite.As a result,M0S2 was found to have poorly crystallized and the limited space of porous N-CMK-3 made its size much small.Then there are moreactive sites in MoS2.Accordingly,MoS2@N-CMK-3 has exhibited good electrocatalytic performance toward HER in acids with a quite small Tafelslope of 32 mV·dec^-1.And more importantly,compared to MoS2@CMK-3,its stability has been greatly improved,which can be attributedto the interaction between M0S2 and nitrogen atoms avoiding aggregation and mass loss.This work provides an idea that doping a porouscarbon support with nitrogen is an effective way to enhance the stability of the catalyst.展开更多
Two-dimensional(2D)transition metal dichalcogenides(TMDs)such as molybdenum disulfide(M0S2)have been intensively investigated because of their exclusive physical properties for advaneed electronics and optoelectronics...Two-dimensional(2D)transition metal dichalcogenides(TMDs)such as molybdenum disulfide(M0S2)have been intensively investigated because of their exclusive physical properties for advaneed electronics and optoelectronics.In the present work,we study the M0S2 transistor based on a novel tri-gate device architecture,with dual-gate(Dual-G)in the channel and the buried side-gate(Side-G)for the source/drain regi ons.All gates can be in depe ndently con trolled without in terfere nee.For a MoS2 sheet with a thick ness of 3.6 nm,the Schottky barrier(SB)and non-overlapped channel region can be effectively tuned by electrostatically doping the source/drain regions with Side-G.Thus,the extri nsic resista nee can be effectively lowered,and a boost of the ON-state cur re nt can be achieved.Mean while,the cha nn el c ontrol remai ns efficient under the Dual-G mode,with an ON-OFF current ratio of 3 x 107 and subthreshold swing of 83 mV/decade.The corresponding band diagram is also discussed to illustrate the device operati on mechanism.This no vel device structure ope ns up a new way toward fabricati on of high-performance devices based on 2D-TMDs.展开更多
基金National Natural Science Foundation of China (Nos. 11604010 and 11674023), 111 Project (No. B170003)Fundamental Research Funds for the Central Universities (No. FRF-BD- 18-004A).
文摘The morphology and structural stability of metal/2D semic on ductor interfaces strongly affect the performa nee of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces has not been well explored particularly at atomic resolution. In this work, we study the structural evoluti on of Au nan oparticles (NPs) on few-layer MoS2 by high resol utio n transmissi on electro n microscopy (HRTEM) an d quan titative high-angle annular dark field seanning TEM. It is found that in the transition of Au from nan oparticles to den drites, a dynamically epitaxial align ment betwee n Au and MoS2 lattices is formed, and Moirc patter ns can be directly observed in HRTEM images due to the mismatch between Au and M0S2 lattices. This epitaxial alignment can occur in ambient conditions, and can also be accelerated by the irradiation of high-energy electron beam. In situ observation clearly reveals the rotation of Au NPs, the atom migration inside Au NPs, and the transfer of Au atoms between neighboring Au NPs, finally leading to the formation of epitaxially aligned Au dendrites on M0S2. The structural evoluti on of metal/2D semico nductor in terfaces at atomic scale can provide valuable information for the design and fabricatio n of the metal/2D semicon ductorn ano-devices with desired physical and chemical performa nces.
基金the National Natural Science Foundation of China(Grant Nos.U1637204,41663012,51775537,and 51775533)the program of the Light of the Chinese Academy of Science in China's Western Region(2015)the Chinese Academy of Science and its Youth Innovation Promotion Association(2016368)for financial support.
文摘The solid lubricant M0S_(2) demonstrates excellent lubricating properties,but it spontaneously oxidizes and absorbs moisture in air,and thus results in poor wear resistance and short wear-life.In this study,the additive g-C_(3)N_(4)(CN)was successfully combined with M0S_(2) via hydrothermal synthesis as a solid lubricant for the first time.Meanwhile,a low friction coefficient(COF,y=0.031)and ultra-long wear-life of CN/M0S_(2) compared to pure M0S_(2) in air were demonstrated.The functional groups and good crystallinity of the lubricant material were characterized via Fourier transform infrared(FTIR)spectroscopy and X-ray diffraction(XRD).The formed valence states in CN/M0S_(2) were analyzed via X-ray photoelectron spectroscopy(XPS).The characterized results of the scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HRTEM)show the morphology and interior crystal phase structure of CN/M0S_(2).From the cross-section analysis,the presence of iron oxide nanoparticles lubricating film is synergistic with CN/M0S_(2) film during the friction process,resulting in its ultra-long wear-life.In particular,the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed.
基金This work was supported by the Nature Science Foundation of Zhejiang Province(No.LY20B010004)and the National Natural Science Foundation of China(Nos.21671152,51672193,51420105002, 21671014).
文摘Developing non-precious metal catalysts with high activity and stability for electrochemical hydrogen evolution reaction(HER)is of great significance in both scie nee and tech no logy.In this work,N-doped CMK-3,which was prepared with a casting method using SBA-15 as thehard template and ammonia as the nitrogen source,has been utilized to hold MoS2 and restrict its growth to form MoS2@N-CMK-3 composite.As a result,M0S2 was found to have poorly crystallized and the limited space of porous N-CMK-3 made its size much small.Then there are moreactive sites in MoS2.Accordingly,MoS2@N-CMK-3 has exhibited good electrocatalytic performance toward HER in acids with a quite small Tafelslope of 32 mV·dec^-1.And more importantly,compared to MoS2@CMK-3,its stability has been greatly improved,which can be attributedto the interaction between M0S2 and nitrogen atoms avoiding aggregation and mass loss.This work provides an idea that doping a porouscarbon support with nitrogen is an effective way to enhance the stability of the catalyst.
基金This work was supported by the National Key Research and Development Program of China(Nos.2016YFA0203900 and 2018YFA0306101)Shanghai Municipal Science and Technology Commission(No.18JC1410300)Natural Science Foundation of China(No.61874154).
文摘Two-dimensional(2D)transition metal dichalcogenides(TMDs)such as molybdenum disulfide(M0S2)have been intensively investigated because of their exclusive physical properties for advaneed electronics and optoelectronics.In the present work,we study the M0S2 transistor based on a novel tri-gate device architecture,with dual-gate(Dual-G)in the channel and the buried side-gate(Side-G)for the source/drain regi ons.All gates can be in depe ndently con trolled without in terfere nee.For a MoS2 sheet with a thick ness of 3.6 nm,the Schottky barrier(SB)and non-overlapped channel region can be effectively tuned by electrostatically doping the source/drain regions with Side-G.Thus,the extri nsic resista nee can be effectively lowered,and a boost of the ON-state cur re nt can be achieved.Mean while,the cha nn el c ontrol remai ns efficient under the Dual-G mode,with an ON-OFF current ratio of 3 x 107 and subthreshold swing of 83 mV/decade.The corresponding band diagram is also discussed to illustrate the device operati on mechanism.This no vel device structure ope ns up a new way toward fabricati on of high-performance devices based on 2D-TMDs.
