Group-V elemental nanofilms were predicted to exhibit interesting physical properties such as nontrivial topological properties due to their strong spin-orbit coupling,the quantum confinement,and surface effect.It was...Group-V elemental nanofilms were predicted to exhibit interesting physical properties such as nontrivial topological properties due to their strong spin-orbit coupling,the quantum confinement,and surface effect.It was reported that the ultrathin Sb nanofilms can undergo a series of topological transitions as a function of the film thickness h:from a topological semimetal(h>7.8 nm)to a topological insulator(7.8 nm>h>2.7 nm),then a quantum spin Hall(QSH)phase(2.7 nm>h>1.0 nm)and a topological trivial semiconductor(h<1.0 nm).Here,we report a comprehensive investigation on the epitaxial growth of Sb nanofilms on highly oriented pyrolytic graphite(HOPG)substrate and the controllable thermal desorption to achieve their specific thickness.The morphology,thickness,atomic structure,and thermal-strain effect of the Sb nanofilms were characterized by a combination study of scanning electron microscopy(SEM),atomic force microscopy(AFM),and scanning tunneling microscopy(STM).The realization of Sb nanofilms with specific thickness paves the way for the further exploring their thickness-dependent topological phase transitions and exotic physical properties.展开更多
Mountain ecosystem provides numerous vital ecosystem services(ESs)to the people residing within or near the mountains worldwide.The mountains provide services such as timber,fibre,fodder,fuelwood,medicine,aesthetic,re...Mountain ecosystem provides numerous vital ecosystem services(ESs)to the people residing within or near the mountains worldwide.The mountains provide services such as timber,fibre,fodder,fuelwood,medicine,aesthetic,recreation,ritual,and religion,and many other services that are vital for the maintenance of the ecosystem.The mountains of Barsoo and Tai-Suru regions in Kargil District are much familiar for their ESs supply,and the residents have utilized these services for years.The present study was focused on the provisioning ESs.We used a random sample approach for household selection and data collection regarding the pre-prepared questionnaire;the number of households was obtained from government census data.The primary ESs(identified by more than 40%of the respondents)were assessed through the direct market valuation method.The direct market valuation method produced an overwhelming value,specifically for grazing and fodder services in both regions of the study area.Results showed that grazing service was valued at 482,346.43 USD/a for Barsoo region and 1,458,099.04 USD/a for Tai-Suru region.Similarly,fodder service of Barsoo and Tai-Suru regions corresponded to values of 69,833.61 and 110,886.06 USD/a,respectively.On the other hand,food service of Barsoo and Tai-Suru regions was valued at 2601.04 and 2969.90 USD/a,respectively,and medicinal service was valued at 757.39 and 4430.94 USD/a in Barsoo and Tai-Suru regions,respectively.In addition,the regions were economically backwards,and the resident’s survival and well-being relied on the mountain ESs.Therefore,it is not possible for the residents to pay services replacement costs if the services need to replace by other means.Unfortunately,such mountain ecosystem is highly prone to climate change and other human activities that would negatively impact the ecosystem functions.Therefore,this study would be helpful for the policymakers of the region to draft any developmental plan/framework by integrating the value of ESs that would be the key to achieving sustainable development.展开更多
Research about two-dimensional (2D) materials is growing exponentially across various scientific and engineering disciplines due to the wealth of unusual physical phenomena that occur when charge transport is confined...Research about two-dimensional (2D) materials is growing exponentially across various scientific and engineering disciplines due to the wealth of unusual physical phenomena that occur when charge transport is confined to a plane. The applications of 2D materials are highly affected by the electrical properties of these mat erials, including curren t dist ribution, surface pot ential, dielectric response, conductivity, perm计tivity, and piezoelectric response. Hence, it is very crucial to characterize these properties at the nanoscale. The Atomic Force Microscopy (AFM)-based techniques are powerful tools that can simultaneously characterize morphology and electrical properties of 2D materials with high spatial resolution, thus being more and more extensively used in this research field. Here, the principles of these AFM techniques are reviewed in detail. After that, their representative applications are further demonstrated in the local characterization of various 2D materials? elcctrical properties.展开更多
The phase behavior of water is a topic of perpetual interest due to its reinai kable anomalous properties and importance to biology,material science,geoscience,nanoscience,etc.It is predicted confined water at interfa...The phase behavior of water is a topic of perpetual interest due to its reinai kable anomalous properties and importance to biology,material science,geoscience,nanoscience,etc.It is predicted confined water at interface can exist in large amounts of crystalline or amorphous states.However,the experimental evidence of coexistence of liquid water phases at interface is still insufficient.Here,a special folding few-layers graphene film was elaborate prepared to form a hydrophobic/hydrophobic interface,which can provide a suited platform to study the structure and properties of confined liquid water.The real-space visualization of intercalated water layers phases at the folding interface is obtained using advanced atomic force microscopy(AFM).The folding graphene interface displays complicated internal interfacial characteristics.The intercalated water molecules present themselves as two phases,low-density liquid(LDL,solid-like)and high-density liquid(HDL,liquid-like),according to their specific mechanical properties taken in two multifrequency-AFM(MF-AFM)modes.Furthermore,the water molecules structural evolution is demonstrated in a series of continuous MF-AFM measurements.The work preliminary confirms the existence of two liquid phases of water in real space and will inspire further experimental work to deeply understanding their liquid dynamics behavior.展开更多
Nanocontact properties of two-dimensional(2D)materials are closely dependent on their unique nanomechanical systems,such as the number of atomic layers and the supporting substrate.Here,we report a direct observation ...Nanocontact properties of two-dimensional(2D)materials are closely dependent on their unique nanomechanical systems,such as the number of atomic layers and the supporting substrate.Here,we report a direct observation of toplayer-dependent crystallographic orientation imaging of 2D materials with the transverse shear microscopy(TSM).Three typical nanomechanical systems,MoS_(2) on the amorphous SiO_(2)/Si,graphene on the amorphous SiO_(2)/Si,and MoS_(2) on the crystallized Al_(2)O_(3),have been investigated in detail.This experimental observation reveals that puckering behaviour mainly occurs on the top layer of 2D materials,which is attributed to its direct contact adhesion with the AFM tip.Furthermore,the result of crystallographic orientation imaging of MoS_(2)/SiO_(2)/Si and MoS_(2)/Al_(2)O_(3) indicated that the underlying crystalline substrates almost do not contribute to the puckering effect of 2D materials.Our work directly revealed the top layer dependent puckering properties of 2D material,and demonstrate the general applications of TSM in the bilayer 2D systems.展开更多
The interlayer bonding in two-dimensional(2D)materials is particularly important because it is not only related to their physical and chemical stability but also afects their mechanical,thermal,elec-tronic,optical,and...The interlayer bonding in two-dimensional(2D)materials is particularly important because it is not only related to their physical and chemical stability but also afects their mechanical,thermal,elec-tronic,optical,and other properties.To address this issue,we report the direct characterization of the interlayer bonding in 2D SnSe using contact-resonance atomic force microscopy(CR-AFM)in.this study.Site-specific CR spectroscopy and CR force spectroscopy measurements are performed on both SnSe and its supporting SiO2/Si substrate comparatively.Based on the cantilever and contact mechanic models,the contact stifness and vertical Young's modulus are evaluated in comparison with SiO2/Si as a reference material.The interlayer bonding of SnSe is further analyzed in combination with the semi-analytical model and density functional theory calculations.The direct characteriza-tion of interlayer interactions using this non-destructive methodology of CR-AFM would facilitate a better understanding of the physical and chemical properties of 2D layered materials,specifically for interlayer intercalation and vertical heterostructures.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21622304,61674045,11604063,and 61911540074)the National Key Research and Development Program of China(Grant No.2016YFA0200700)+2 种基金the Strategic Priority Research Program and Key Research Program of Frontier Sciences and Instrument Developing Project(Chinese Academy of Sciences,CAS)(Grant Nos.XDB30000000,QYZDB-SSW-SYS031,and YZ201418)Z.H.Cheng was supported by Distinguished Technical Talents Project and Youth Innovation Promotion Association CAS,the Fundamental Research Funds for the Central Universities,Chinathe Research Funds of Renmin University of China(Grant No.18XNLG01).
文摘Group-V elemental nanofilms were predicted to exhibit interesting physical properties such as nontrivial topological properties due to their strong spin-orbit coupling,the quantum confinement,and surface effect.It was reported that the ultrathin Sb nanofilms can undergo a series of topological transitions as a function of the film thickness h:from a topological semimetal(h>7.8 nm)to a topological insulator(7.8 nm>h>2.7 nm),then a quantum spin Hall(QSH)phase(2.7 nm>h>1.0 nm)and a topological trivial semiconductor(h<1.0 nm).Here,we report a comprehensive investigation on the epitaxial growth of Sb nanofilms on highly oriented pyrolytic graphite(HOPG)substrate and the controllable thermal desorption to achieve their specific thickness.The morphology,thickness,atomic structure,and thermal-strain effect of the Sb nanofilms were characterized by a combination study of scanning electron microscopy(SEM),atomic force microscopy(AFM),and scanning tunneling microscopy(STM).The realization of Sb nanofilms with specific thickness paves the way for the further exploring their thickness-dependent topological phase transitions and exotic physical properties.
基金financially supported by the Council of Scientific and Industrial Research,New Delhi,Government of India in the form of the Junior Research Fellowship(CSIR-JRF)(09/135(0884)/2019-EMR-I)the second author is also funded by the University Grants Commission(UGC),New Delhi,Government of India in the form of Junior Research Fellowship(UGC-JRF)[UGC Ref.No.:453/(CSIR-UGC NET DEC.2018)]。
文摘Mountain ecosystem provides numerous vital ecosystem services(ESs)to the people residing within or near the mountains worldwide.The mountains provide services such as timber,fibre,fodder,fuelwood,medicine,aesthetic,recreation,ritual,and religion,and many other services that are vital for the maintenance of the ecosystem.The mountains of Barsoo and Tai-Suru regions in Kargil District are much familiar for their ESs supply,and the residents have utilized these services for years.The present study was focused on the provisioning ESs.We used a random sample approach for household selection and data collection regarding the pre-prepared questionnaire;the number of households was obtained from government census data.The primary ESs(identified by more than 40%of the respondents)were assessed through the direct market valuation method.The direct market valuation method produced an overwhelming value,specifically for grazing and fodder services in both regions of the study area.Results showed that grazing service was valued at 482,346.43 USD/a for Barsoo region and 1,458,099.04 USD/a for Tai-Suru region.Similarly,fodder service of Barsoo and Tai-Suru regions corresponded to values of 69,833.61 and 110,886.06 USD/a,respectively.On the other hand,food service of Barsoo and Tai-Suru regions was valued at 2601.04 and 2969.90 USD/a,respectively,and medicinal service was valued at 757.39 and 4430.94 USD/a in Barsoo and Tai-Suru regions,respectively.In addition,the regions were economically backwards,and the resident’s survival and well-being relied on the mountain ESs.Therefore,it is not possible for the residents to pay services replacement costs if the services need to replace by other means.Unfortunately,such mountain ecosystem is highly prone to climate change and other human activities that would negatively impact the ecosystem functions.Therefore,this study would be helpful for the policymakers of the region to draft any developmental plan/framework by integrating the value of ESs that would be the key to achieving sustainable development.
基金the National Natural Science Foundation of China (NSFC)(Nos. 21622304, 61674045, and 11604063)the Ministry of Science and Technology (MOST) of China (No. 2016YFA0200700)+2 种基金the Strategic Priority Research Program, the Key Research Program of Frontier Sciences and Instrument Developing Project of Chinese Academy of Sciences (CAS)(Nos. XDB30000000, QYZDB-SSW-SYS031, and YZ201418)Osaka University's International Joint Research Promotion Program (Nos. J171013014 and J171013007)Z.H. Cheng was supported by Distinguished Technical Talents Project and Youth Innovation Promotion Association CAS, the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China (No. 18XNLG01).
文摘Research about two-dimensional (2D) materials is growing exponentially across various scientific and engineering disciplines due to the wealth of unusual physical phenomena that occur when charge transport is confined to a plane. The applications of 2D materials are highly affected by the electrical properties of these mat erials, including curren t dist ribution, surface pot ential, dielectric response, conductivity, perm计tivity, and piezoelectric response. Hence, it is very crucial to characterize these properties at the nanoscale. The Atomic Force Microscopy (AFM)-based techniques are powerful tools that can simultaneously characterize morphology and electrical properties of 2D materials with high spatial resolution, thus being more and more extensively used in this research field. Here, the principles of these AFM techniques are reviewed in detail. After that, their representative applications are further demonstrated in the local characterization of various 2D materials? elcctrical properties.
基金the Ministry of Science and Technology(MOST)of China(No.2016YFA0200700)the National Natural Science Foun-dation of China(NSFC)(Nos.21622304,61674045,and 11604063)+1 种基金the Strategic Priority Research Program,the Key Research Program of Frontier Sciences and Instrument Developing Project of Chinese Academy of Sciences(CAS)(Nos.XDB30000000,QYZDB-SSW-SYS031,and YZ201418)Z.H.Cheng was supported by Distinguished Technical Talents Project and Youth Innovation Promotion Association CAS,the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China(No.18XNLG01).
文摘The phase behavior of water is a topic of perpetual interest due to its reinai kable anomalous properties and importance to biology,material science,geoscience,nanoscience,etc.It is predicted confined water at interface can exist in large amounts of crystalline or amorphous states.However,the experimental evidence of coexistence of liquid water phases at interface is still insufficient.Here,a special folding few-layers graphene film was elaborate prepared to form a hydrophobic/hydrophobic interface,which can provide a suited platform to study the structure and properties of confined liquid water.The real-space visualization of intercalated water layers phases at the folding interface is obtained using advanced atomic force microscopy(AFM).The folding graphene interface displays complicated internal interfacial characteristics.The intercalated water molecules present themselves as two phases,low-density liquid(LDL,solid-like)and high-density liquid(HDL,liquid-like),according to their specific mechanical properties taken in two multifrequency-AFM(MF-AFM)modes.Furthermore,the water molecules structural evolution is demonstrated in a series of continuous MF-AFM measurements.The work preliminary confirms the existence of two liquid phases of water in real space and will inspire further experimental work to deeply understanding their liquid dynamics behavior.
基金This work was supported by the National Natural Science Foundation of China(NSFC,Grant Nos.21622304,61674045,and 11604063)Ministry of Science and Technology(MOST)of China(Grant No.2016YFA0200700)+5 种基金Strategic Priority Research Program,Key Research Program of Frontier Sciences and Instrument Developing Project of Chinese Academy of Sciences(CASGrant Nos.XDB30000000,QYZDB-SSW-SYS031,and YZ201418)Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science(JSPS)from the Ministry of Education,Culture,Sports,Science,and Technology of Japan(Grant Nos.JP16H06327,JP16H06504,JP17H01061,and JP17H010610)Osaka University’s International Joint Research Promotion Program(Grant Nos.J171013014,J171013007,J181013006,and Ja19990011)Z.H.Cheng was supported by Distinguished Technical Talents Project and Youth Innovation Promotion Association CAS,the Fundamental Research Funds for the Central Universities,and the Research Funds of Renmin University of China(Grant No.18XNLG01)S.Chen appreciate the support from Beijing Natural Science Foundation(Grant No.2192024).
文摘Nanocontact properties of two-dimensional(2D)materials are closely dependent on their unique nanomechanical systems,such as the number of atomic layers and the supporting substrate.Here,we report a direct observation of toplayer-dependent crystallographic orientation imaging of 2D materials with the transverse shear microscopy(TSM).Three typical nanomechanical systems,MoS_(2) on the amorphous SiO_(2)/Si,graphene on the amorphous SiO_(2)/Si,and MoS_(2) on the crystallized Al_(2)O_(3),have been investigated in detail.This experimental observation reveals that puckering behaviour mainly occurs on the top layer of 2D materials,which is attributed to its direct contact adhesion with the AFM tip.Furthermore,the result of crystallographic orientation imaging of MoS_(2)/SiO_(2)/Si and MoS_(2)/Al_(2)O_(3) indicated that the underlying crystalline substrates almost do not contribute to the puckering effect of 2D materials.Our work directly revealed the top layer dependent puckering properties of 2D material,and demonstrate the general applications of TSM in the bilayer 2D systems.
基金This project was supported by the Min-istry of Science and Technology(MOST)of China(Grant Nos.2016YFA0200700 and 2018YFE0202700)the National Natural Science Foundation of China(NSFC)(Grant Nos.21622304,61674045,11604063,11622437,11974422,61911540074,11804247,and 61674171)+2 种基金Strategic Priority Research Program,Key Research Program of Frontier Sciences,and Instrument Developing Project of Chinese Academy of Sciences(CAS)(Grant Nos.XDB000000,QYZDB-SSW-8Y5031,and YZ201418)Z.H.Cheng was supportod by Distinguished Technical Talents Project and Youth Innovation Promotion Association CAS,Fundamental Research Funds for the Central Universities,and Research Funds of Renmin University of China(Grant Nos.18XNLG01 and 19XNQ025)Calculations were performed at the Physics Lab of High-Performance Computing of Renmin University of China and Shanghal Supercomputer Center.
文摘The interlayer bonding in two-dimensional(2D)materials is particularly important because it is not only related to their physical and chemical stability but also afects their mechanical,thermal,elec-tronic,optical,and other properties.To address this issue,we report the direct characterization of the interlayer bonding in 2D SnSe using contact-resonance atomic force microscopy(CR-AFM)in.this study.Site-specific CR spectroscopy and CR force spectroscopy measurements are performed on both SnSe and its supporting SiO2/Si substrate comparatively.Based on the cantilever and contact mechanic models,the contact stifness and vertical Young's modulus are evaluated in comparison with SiO2/Si as a reference material.The interlayer bonding of SnSe is further analyzed in combination with the semi-analytical model and density functional theory calculations.The direct characteriza-tion of interlayer interactions using this non-destructive methodology of CR-AFM would facilitate a better understanding of the physical and chemical properties of 2D layered materials,specifically for interlayer intercalation and vertical heterostructures.
