Germanene nanostrips(GeNSs)have garnered significant attention in modern semiconductor technology due to their exceptional physical characteristics,positioning them as promising candidates for a wide range of applicat...Germanene nanostrips(GeNSs)have garnered significant attention in modern semiconductor technology due to their exceptional physical characteristics,positioning them as promising candidates for a wide range of applications.GeNSs exhibit a two-dimensional(buckled)honeycomb-like lattice,which is similar to germanene but with controllable bandgaps.The modeling of GeNSs is essential for developing appropriate synthesis methods as it enables understanding and controlling the growth process of these systems.Indeed,one can adjust the strip width,which in turn can tune the bandgap and plasmonic response of the material to meet specific device requirements.In this study,the objective is to investigate the electronic behav-ior and THz plasmon features of GeNSs(≥100 nm wide).A semi-analytical model based on the charge-carrier velocity of free-standing germanene is utilized for this purpose.The charge-carrier velocity of freestanding germanene is determined through the GW approximation(V_(F)=0.702×10^(6)m·s^(−1)).Within the width range of 100 to 500 nm,GeNSs exhibit narrow bandgaps,typi-cally measuring only a few meV.Specifically,upon analysis,it was found that the bandgaps of the investigated GeNSs ranged between 29 and 6 meV.As well,these nanostrips exhibit√q-like plasmon dispersions,with their connected plasmonic fre-quency(≤30 THz)capable of being manipulated by varying parameters such as strip width,excitation plasmon angle,and sam-ple quality.These manipulations can lead to frequency variations,either increasing or decreasing,as well as shifts towards larger momentum values.The outcomes of our study serve as a foundational motivation for future experiments,and further con-firmation is needed to validate the reported results.展开更多
The electronic structure and optical properties of bilayer germanene under different warpages are studied by the first-principles method of density functional theory.The effects of warpages on the electronic structure...The electronic structure and optical properties of bilayer germanene under different warpages are studied by the first-principles method of density functional theory.The effects of warpages on the electronic structure and optical properties of bilayer germanene are analyzed.The results of the electronic structure study show that the bottom of the conduction band of bilayer germanene moves to the lower energy direction with the increase of warpages at the K point,and the top of the valence band stays constant at the K point,and so the band gap decreases with the increase of warpage.When the warpage is 0.075 nm,the top of the valence band of bilayer germanene changes from K point to G point,and the bilayer germanene be-comes an indirect band gap semiconductor.This is an effective means to modulate the conversion of bilayer germanene between direct band gap semiconductor and indirect band gap semiconductor by adjusting the band structure of bilayer ger-manene effectively.The study of optical properties shows that the effect of warpage on the optical properties of bilayer ger-manene is mainly distributed in the ultraviolet and visible regions,and the warpage can effectively regulate the electronic struc-ture and optical properties of bilayer germanene.When the warpage is 0.069 nm,the first peak of dielectric function and extinc-tion coefficient is the largest,and the energy corresponding to the absorption band edge is the smallest.Therefore,the elec-tron utilization rate is the best when the warpage is 0.069 nm.展开更多
Germanene,the germanium analogue of graphene,shares many properties with its carbon counterpart.Both materials are two-dimensional materials that host Dirac fermions.There are,however,also a few important differences ...Germanene,the germanium analogue of graphene,shares many properties with its carbon counterpart.Both materials are two-dimensional materials that host Dirac fermions.There are,however,also a few important differences between these two materials:(1)graphene has a planar honeycomb lattice,whereas germanene’s honeycomb lattice is buckled and(2)the spin-orbit gap in germanene is predicted to be about three orders of magnitude larger than the spin-orbit gap in graphene(24 meV for germanene versus 20μeV for graphene).Surprisingly,scanning tunneling spectra recorded on germanene layers synthesized on different substrates do not show any sign of the presence of a spin-orbit gap.To date the exact origin of the absence of this spin-orbit gap in the scanning tunneling spectra of germanene has remained a mystery.In this work we show that the absence of the spin-orbit gap can be explained by germanene’s exceptionally low work function of only 3.8 eV.The difference in work function between germanene and the scanning tunneling microscopy tip(the work functions of most commonly used STM tips are in the range of 4.5 to 5.5 eV)gives rise to an electric field in the tunnel junction.This electric field results in a strong suppression of the size of the spin-orbit gap.展开更多
The structural and vibrational properties of two-dimensional hexagonal silicon （silicene） and germanium （germanene） are investigated by means of first-principles calculations. It is predicted that the silicene （g...The structural and vibrational properties of two-dimensional hexagonal silicon （silicene） and germanium （germanene） are investigated by means of first-principles calculations. It is predicted that the silicene （germanene） structure with a small buckling of 0.44 ,~ （0.7/k） and bond lengths of 2.28 ,~ （2.44 .~） is energetically the most favorable, and it does not exhibit imaginary phonon mode. The calculated non-resonance Raman spectra of silicene are characterized by a main peak at about 575 cm-1, namely the G-like peak. For germanene, the highest peak is at about 290 cm-1. Extensive calculations on armchair silicene nanoribbons and armchair germanene nanoribbons are also performed, with and without hydrogenation of the edges. The studies reveal other Raman peaks mainly distributed at lower frequencies than the G-like peak which could be attributed to the defects at the edges of the ribbons, thus not present in the Raman spectra of non-defective silicene and germanene. Particularly the Raman peak corresponding to the D mode is found to be located at around 515 cm-1 for silicene and 270 cm-1 for germanene. The calculated G-like and the D peaks are likely the fingerprints of the Raman spectra of the low-buckled structures of silicene and germanene.展开更多
The simultaneous formati on of single domain(3×3)and multi domai n(√7×√7)R(±19.1°)germa nene phases on Al(111)surface in thesub-monolayer range was studied using seanning tunneling microscopy(STM...The simultaneous formati on of single domain(3×3)and multi domai n(√7×√7)R(±19.1°)germa nene phases on Al(111)surface in thesub-monolayer range was studied using seanning tunneling microscopy(STM)and density functional theory(DFT)based simulations.Experimental results revealed that both germa nene phases nu cleate and grow in dependently from each other and regardless of Al substratetemperature within significantly expanded range Ts=27-200℃.Our results unambiguously showed that STM images with hexagonalcontrast yield correct-resolved structure for both germanene phases,while honeycomb contrast is a result of an artificial tip-induced STM resolution.First-principles calculations suggested atomic models with strongly buckled germanene(2×2)/Al(111)(3×3)and(√3×√3)R30°/Al(111)(√7×√7)R(±19.1°)with one of eight and one of six Ge atoms protruding upward respectively,that consistently describe the experimentally observed STM images both for single and multi domai n surface phases.According to the DFT based simulati ons both germa nene(2×2)and(√3×√3)R30°superstructures have a stretched lattice strain with respect to the ideal free-standing germa nene by 6.2%and 13.9%,respectively.Hence,numerous small domains separated by domain boundaries in the(√3×√3)R30°/Al(111)(√7×√7)R(±19.1°)germanenephase tend to reduce the surface energy and prevent the formation of extended single domains,in contrast to the(2×2)/Al(111)(3×3)phase.However,our experimental results showed that the nucleation and growth of germa nene on Al(111)surface yield strong modifications of Alsurface even at room temperature(RT),which may be contributed to the formation of Al-Ge alloy due to Ge surface solid-states reactivitythat was ignored in recent studies.It is already evident from our present findings that the role of Al atoms in the formation of(3×3)and(√7×√7)R(±19.1°)germa nene phases is worthy to be carefully studied in the future,which could be an important knowledge for large-quantityfabrication of germanene on aluminum.展开更多
Two-dimension(2D)magnets have recently developed into a class of stoichiometric materials with prospective applications in ultra-compact spintronics and quantum computing.Their functionality is particularly rich when ...Two-dimension(2D)magnets have recently developed into a class of stoichiometric materials with prospective applications in ultra-compact spintronics and quantum computing.Their functionality is particularly rich when different magnetic orders are competing in the same material.Metalloxenes REX2(RE=Eu,Gd;X=Si,Ge),silicene or germanene—heavy counterparts of graphene—coupled with a layer of rare-earth metals,evolve from three-dimension(3D)antiferromagnets in multilayer structures to 2D ferromagnets in a few monolayers.This evolution,however,does not lead to fully saturated 2D ferromagnetism,pointing at a possibility of coexisting/competing magnetic states.Here,REX2 magnetism is explored with element-selective X-ray magnetic circular dichroism(XMCD).The measurements are carried out for GdSi2,EuSi2,GdGe2,and EuGe2 of different thicknesses down to 1 monolayer employing K absorption edges of Si and Ge as well as M and L edges of the rare-earths.They access the magnetic state in REX2 and determine the seat of magnetism,orbital,and spin contributions to the magnetic moment.High-field measurements probe remnants of the bulk antiferromagnetism in 2D REX2.The results provide a new platform for studies of complex magnetic structures in 2D materials.展开更多
As a member of Xenes family,germanene has excellent nonlinear saturable absorption characteristics.In this work,we prepared germanene nanosheets by liquid phase exfoliation and measured their saturation intensity as 0...As a member of Xenes family,germanene has excellent nonlinear saturable absorption characteristics.In this work,we prepared germanene nanosheets by liquid phase exfoliation and measured their saturation intensity as 0.6 GW/cm^(2) with a modulation depth of 8%.Then,conventional solitons with a pulse width of 946 fs and high-energy noise-like pulses with a pulse width of 784 fs were obtained by using germanene nanosheet as a saturable absorber for a mode-locked Erbium-doped fber laser.The characteristics of the two types of pulses were investigated experimentally.The results reveal that germanene has great potential for modulation devices in ultrafast lasers and can be used as a material for creation of excellent nonlinear optical devices to explore richer applications in ultrafast photonics.展开更多
Graphene,an emerging fabric of carbon atoms,has manifested its versatility in all kinds of fields encompassing electronics,optoelectronics,thermoelectrics,taking advantage of its excellent mechanical strength,exceptio...Graphene,an emerging fabric of carbon atoms,has manifested its versatility in all kinds of fields encompassing electronics,optoelectronics,thermoelectrics,taking advantage of its excellent mechanical strength,exceptional electronic and thermal conductivities,high surface specific area,and so forth.The prosperity of graphene never seen before has led the attention to silicene,siloxene,germanene,stanene,and plumbene due to their promising applications in the quantum spin Hall effect,topological insulator,batteries,capacitors,catalysis,and topological superconductivity.Herein,we review the existing production methods,numerous applications of two-dimensional group-IVA materials,and critically discuss the challenges of these materials,providing potential implications to the exploration of uncharted material systems.展开更多
As a new type of green energy, lithium-ion battery(LIB) has been widely used in various electric portable devices because of its high-voltage, large specific capacity, long cycle life and environmental friendliness [1...As a new type of green energy, lithium-ion battery(LIB) has been widely used in various electric portable devices because of its high-voltage, large specific capacity, long cycle life and environmental friendliness [1,2]. However, today’s anode materials of commercial LIBs cannot meet the further development requirements of smart devices and electric car due to the limitations of the electrode capacity(e.g. 372 mAh g-1 for graphite).展开更多
In this article, we investigate the predictions of the first principles on structural stability, electronic and mechanical properties of 2D nanostructures: graphene, silicene, germanene and stenane. The electronic ban...In this article, we investigate the predictions of the first principles on structural stability, electronic and mechanical properties of 2D nanostructures: graphene, silicene, germanene and stenane. The electronic band structure and density of states in all these 2D materials are found to be generic in nature. A small band gap is generated in all the reported materials other than graphene. The linearity at the Dirac cone changes to quadratic, from graphene to stenane and a perfect semimetalicity is exhibited only by graphene. All other 2D structures tend to become semiconductors with an infinitesimal band gap. Bonding characteristics are revealed by density of states histogram, charge density contour, and Mulliken population analysis. Among all 2D materials graphene exhibits exotic mechanical properties. Analysis by born stability criteria and the calculation of formation enthalpies envisages the structural stability of all the structures in the 2D form. The calculated second order elastic stiffness tensor is used to determine the moduli of elasticity in turn to explore the mechanical properties of all these structures for the prolific use in engineering science. Graphene is found to be the strongest material but brittle in nature. Germanene and stenane exhibit ductile nature and hence could be easily incorporated with the existing technology in the semiconductor industry on substrates.展开更多
Two-dimensional(2D)materials based on group IVA elements have attracted extensive attention owing to their rich chemical structures and novel proper-ties.This comprehensive review focuses on the phases of Ge monoeleme...Two-dimensional(2D)materials based on group IVA elements have attracted extensive attention owing to their rich chemical structures and novel proper-ties.This comprehensive review focuses on the phases of Ge monoelemental and binary 2D materials including germanene and its derivatives,Ge-IVA binary compounds,Ge-VA binary compounds,and Ge-VIA binary compounds.The latest progress in predictive modeling,fabrication,and fundamental and physical property modulation of their stable 2D configurations are presented.Accordingly,various interesting applications of these Ge-based 2D materials are discussed,particularly field effect transistors,photodetectors,optical devices,catalysts,energy storage devices,solar cells,thermoelectric devices,sensors,biomedical materials,and spintronic devices.Finally,this review con-cludes with a few perspectives and an outlook for quickly expanding the appli-cation scope Ge-based 2D materials based on recent developments.展开更多
基金This work was supported by Universidad Técnica Particular de Loja(UTPL-Ecuador)under the project:“Análisis de las propiedades térmicas del grafeno y zeolite”,Grant No.:PROY_INV_QU_2022_362.T.T.,M.G.,and C.V.G.wish to thank the Ecuadorian National Department of Sciences and Technology(SENESCYT).This work was partially supported by LNF-INFN:Progetto HPSWFOOD Regione Lazio-CUP I35F20000400005.
文摘Germanene nanostrips(GeNSs)have garnered significant attention in modern semiconductor technology due to their exceptional physical characteristics,positioning them as promising candidates for a wide range of applications.GeNSs exhibit a two-dimensional(buckled)honeycomb-like lattice,which is similar to germanene but with controllable bandgaps.The modeling of GeNSs is essential for developing appropriate synthesis methods as it enables understanding and controlling the growth process of these systems.Indeed,one can adjust the strip width,which in turn can tune the bandgap and plasmonic response of the material to meet specific device requirements.In this study,the objective is to investigate the electronic behav-ior and THz plasmon features of GeNSs(≥100 nm wide).A semi-analytical model based on the charge-carrier velocity of free-standing germanene is utilized for this purpose.The charge-carrier velocity of freestanding germanene is determined through the GW approximation(V_(F)=0.702×10^(6)m·s^(−1)).Within the width range of 100 to 500 nm,GeNSs exhibit narrow bandgaps,typi-cally measuring only a few meV.Specifically,upon analysis,it was found that the bandgaps of the investigated GeNSs ranged between 29 and 6 meV.As well,these nanostrips exhibit√q-like plasmon dispersions,with their connected plasmonic fre-quency(≤30 THz)capable of being manipulated by varying parameters such as strip width,excitation plasmon angle,and sam-ple quality.These manipulations can lead to frequency variations,either increasing or decreasing,as well as shifts towards larger momentum values.The outcomes of our study serve as a foundational motivation for future experiments,and further con-firmation is needed to validate the reported results.
基金supported by the Science and Technology Foundation of Guizhou Province,China(Nos.1Y[2020]200,1Y[2020]205)the Youth Science and Technology Talents Growth Fund Program of the Ministry of Education Province,China(Nos.KY[2021]105,KY[2021]103).
文摘The electronic structure and optical properties of bilayer germanene under different warpages are studied by the first-principles method of density functional theory.The effects of warpages on the electronic structure and optical properties of bilayer germanene are analyzed.The results of the electronic structure study show that the bottom of the conduction band of bilayer germanene moves to the lower energy direction with the increase of warpages at the K point,and the top of the valence band stays constant at the K point,and so the band gap decreases with the increase of warpage.When the warpage is 0.075 nm,the top of the valence band of bilayer germanene changes from K point to G point,and the bilayer germanene be-comes an indirect band gap semiconductor.This is an effective means to modulate the conversion of bilayer germanene between direct band gap semiconductor and indirect band gap semiconductor by adjusting the band structure of bilayer ger-manene effectively.The study of optical properties shows that the effect of warpage on the optical properties of bilayer ger-manene is mainly distributed in the ultraviolet and visible regions,and the warpage can effectively regulate the electronic struc-ture and optical properties of bilayer germanene.When the warpage is 0.069 nm,the first peak of dielectric function and extinc-tion coefficient is the largest,and the energy corresponding to the absorption band edge is the smallest.Therefore,the elec-tron utilization rate is the best when the warpage is 0.069 nm.
基金the Nederlandse Organisatie voor Wetenschappelijk Onderzoek(NWO)for financial support.
文摘Germanene,the germanium analogue of graphene,shares many properties with its carbon counterpart.Both materials are two-dimensional materials that host Dirac fermions.There are,however,also a few important differences between these two materials:(1)graphene has a planar honeycomb lattice,whereas germanene’s honeycomb lattice is buckled and(2)the spin-orbit gap in germanene is predicted to be about three orders of magnitude larger than the spin-orbit gap in graphene(24 meV for germanene versus 20μeV for graphene).Surprisingly,scanning tunneling spectra recorded on germanene layers synthesized on different substrates do not show any sign of the presence of a spin-orbit gap.To date the exact origin of the absence of this spin-orbit gap in the scanning tunneling spectra of germanene has remained a mystery.In this work we show that the absence of the spin-orbit gap can be explained by germanene’s exceptionally low work function of only 3.8 eV.The difference in work function between germanene and the scanning tunneling microscopy tip(the work functions of most commonly used STM tips are in the range of 4.5 to 5.5 eV)gives rise to an electric field in the tunnel junction.This electric field results in a strong suppression of the size of the spin-orbit gap.
文摘The structural and vibrational properties of two-dimensional hexagonal silicon （silicene） and germanium （germanene） are investigated by means of first-principles calculations. It is predicted that the silicene （germanene） structure with a small buckling of 0.44 ,~ （0.7/k） and bond lengths of 2.28 ,~ （2.44 .~） is energetically the most favorable, and it does not exhibit imaginary phonon mode. The calculated non-resonance Raman spectra of silicene are characterized by a main peak at about 575 cm-1, namely the G-like peak. For germanene, the highest peak is at about 290 cm-1. Extensive calculations on armchair silicene nanoribbons and armchair germanene nanoribbons are also performed, with and without hydrogenation of the edges. The studies reveal other Raman peaks mainly distributed at lower frequencies than the G-like peak which could be attributed to the defects at the edges of the ribbons, thus not present in the Raman spectra of non-defective silicene and germanene. Particularly the Raman peak corresponding to the D mode is found to be located at around 515 cm-1 for silicene and 270 cm-1 for germanene. The calculated G-like and the D peaks are likely the fingerprints of the Raman spectra of the low-buckled structures of silicene and germanene.
文摘The simultaneous formati on of single domain(3×3)and multi domai n(√7×√7)R(±19.1°)germa nene phases on Al(111)surface in thesub-monolayer range was studied using seanning tunneling microscopy(STM)and density functional theory(DFT)based simulations.Experimental results revealed that both germa nene phases nu cleate and grow in dependently from each other and regardless of Al substratetemperature within significantly expanded range Ts=27-200℃.Our results unambiguously showed that STM images with hexagonalcontrast yield correct-resolved structure for both germanene phases,while honeycomb contrast is a result of an artificial tip-induced STM resolution.First-principles calculations suggested atomic models with strongly buckled germanene(2×2)/Al(111)(3×3)and(√3×√3)R30°/Al(111)(√7×√7)R(±19.1°)with one of eight and one of six Ge atoms protruding upward respectively,that consistently describe the experimentally observed STM images both for single and multi domai n surface phases.According to the DFT based simulati ons both germa nene(2×2)and(√3×√3)R30°superstructures have a stretched lattice strain with respect to the ideal free-standing germa nene by 6.2%and 13.9%,respectively.Hence,numerous small domains separated by domain boundaries in the(√3×√3)R30°/Al(111)(√7×√7)R(±19.1°)germanenephase tend to reduce the surface energy and prevent the formation of extended single domains,in contrast to the(2×2)/Al(111)(3×3)phase.However,our experimental results showed that the nucleation and growth of germa nene on Al(111)surface yield strong modifications of Alsurface even at room temperature(RT),which may be contributed to the formation of Al-Ge alloy due to Ge surface solid-states reactivitythat was ignored in recent studies.It is already evident from our present findings that the role of Al atoms in the formation of(3×3)and(√7×√7)R(±19.1°)germa nene phases is worthy to be carefully studied in the future,which could be an important knowledge for large-quantityfabrication of germanene on aluminum.
基金This work was supported by National Research Center(NRC)“Kurchatov Institute”(No.1359,characterization)the Russian Science Foundation(No.19-19-00009(synthesis)and No.20-79-10028(magnetization measurements))。
文摘Two-dimension(2D)magnets have recently developed into a class of stoichiometric materials with prospective applications in ultra-compact spintronics and quantum computing.Their functionality is particularly rich when different magnetic orders are competing in the same material.Metalloxenes REX2(RE=Eu,Gd;X=Si,Ge),silicene or germanene—heavy counterparts of graphene—coupled with a layer of rare-earth metals,evolve from three-dimension(3D)antiferromagnets in multilayer structures to 2D ferromagnets in a few monolayers.This evolution,however,does not lead to fully saturated 2D ferromagnetism,pointing at a possibility of coexisting/competing magnetic states.Here,REX2 magnetism is explored with element-selective X-ray magnetic circular dichroism(XMCD).The measurements are carried out for GdSi2,EuSi2,GdGe2,and EuGe2 of different thicknesses down to 1 monolayer employing K absorption edges of Si and Ge as well as M and L edges of the rare-earths.They access the magnetic state in REX2 and determine the seat of magnetism,orbital,and spin contributions to the magnetic moment.High-field measurements probe remnants of the bulk antiferromagnetism in 2D REX2.The results provide a new platform for studies of complex magnetic structures in 2D materials.
基金funded by the National Natural Science Foundation of China(Grant No.62005094)the Natural Science Foundation of Shandong Province(No.ZR2021MF128)+1 种基金the Key research program of Shandong Province(2020JMRH0302)the Industrial Chain Program of Shandong laser Equipment Innovation and Entrepreneurship Community(JGCYL2022-5).
文摘As a member of Xenes family,germanene has excellent nonlinear saturable absorption characteristics.In this work,we prepared germanene nanosheets by liquid phase exfoliation and measured their saturation intensity as 0.6 GW/cm^(2) with a modulation depth of 8%.Then,conventional solitons with a pulse width of 946 fs and high-energy noise-like pulses with a pulse width of 784 fs were obtained by using germanene nanosheet as a saturable absorber for a mode-locked Erbium-doped fber laser.The characteristics of the two types of pulses were investigated experimentally.The results reveal that germanene has great potential for modulation devices in ultrafast lasers and can be used as a material for creation of excellent nonlinear optical devices to explore richer applications in ultrafast photonics.
基金This study was supported by the National Key R&D Program of China(2017YFB1104300 and 2016YFA0200200)Natural Science Foundation of China(NSFC)(No.21671020,51433005 and 51673026)+1 种基金NSFC-MAECI(51861135202),Beijing Natural Science Foundation(2172049)Analysis&Testing Center,Beijing Institute of Technology.
文摘Graphene,an emerging fabric of carbon atoms,has manifested its versatility in all kinds of fields encompassing electronics,optoelectronics,thermoelectrics,taking advantage of its excellent mechanical strength,exceptional electronic and thermal conductivities,high surface specific area,and so forth.The prosperity of graphene never seen before has led the attention to silicene,siloxene,germanene,stanene,and plumbene due to their promising applications in the quantum spin Hall effect,topological insulator,batteries,capacitors,catalysis,and topological superconductivity.Herein,we review the existing production methods,numerous applications of two-dimensional group-IVA materials,and critically discuss the challenges of these materials,providing potential implications to the exploration of uncharted material systems.
基金supported by National Key Research and Development Program of China (No.2017YFB0702100)the National Natural Science Foundation of China (No.11404017)+4 种基金Technology Foundation for Selected Overseas Chinese Scholar, Ministry of Human Resources and Social Security of China, Beijing Natural Science Foundation (No.20192029)supported by the European Regional Development Fund in the IT4Innovations National Supercomputing Center-Path to Exascale project, No.CZ.02.1.01/ 0.0/0.0/16_013/0001791 within the Operational Programme Research, Development and Education by the Ministry of Education, Youth, and Sport of the Czech Republicgrant No.17-27790S of the Czech Science FoundationsMobility grant No.8J18DE004 of the Ministry of Education, Youngth and Sports of the Czech RepublicSGS No.SP2019/110。
文摘As a new type of green energy, lithium-ion battery(LIB) has been widely used in various electric portable devices because of its high-voltage, large specific capacity, long cycle life and environmental friendliness [1,2]. However, today’s anode materials of commercial LIBs cannot meet the further development requirements of smart devices and electric car due to the limitations of the electrode capacity(e.g. 372 mAh g-1 for graphite).
文摘In this article, we investigate the predictions of the first principles on structural stability, electronic and mechanical properties of 2D nanostructures: graphene, silicene, germanene and stenane. The electronic band structure and density of states in all these 2D materials are found to be generic in nature. A small band gap is generated in all the reported materials other than graphene. The linearity at the Dirac cone changes to quadratic, from graphene to stenane and a perfect semimetalicity is exhibited only by graphene. All other 2D structures tend to become semiconductors with an infinitesimal band gap. Bonding characteristics are revealed by density of states histogram, charge density contour, and Mulliken population analysis. Among all 2D materials graphene exhibits exotic mechanical properties. Analysis by born stability criteria and the calculation of formation enthalpies envisages the structural stability of all the structures in the 2D form. The calculated second order elastic stiffness tensor is used to determine the moduli of elasticity in turn to explore the mechanical properties of all these structures for the prolific use in engineering science. Graphene is found to be the strongest material but brittle in nature. Germanene and stenane exhibit ductile nature and hence could be easily incorporated with the existing technology in the semiconductor industry on substrates.
基金National Natural Science Foundation of China,Grant/Award Numbers:52103093,52130303,52173078China Postdoctoral Science Foundation,Grant/Award Numbers:2021M702424,2022T150172+1 种基金the Young Elite Scientists Sponsorship Program by CAST,Grant/Award Number:2021QNRC001the Seed Foundation of Tianjin University,Grant/Award Number:220636。
文摘Two-dimensional(2D)materials based on group IVA elements have attracted extensive attention owing to their rich chemical structures and novel proper-ties.This comprehensive review focuses on the phases of Ge monoelemental and binary 2D materials including germanene and its derivatives,Ge-IVA binary compounds,Ge-VA binary compounds,and Ge-VIA binary compounds.The latest progress in predictive modeling,fabrication,and fundamental and physical property modulation of their stable 2D configurations are presented.Accordingly,various interesting applications of these Ge-based 2D materials are discussed,particularly field effect transistors,photodetectors,optical devices,catalysts,energy storage devices,solar cells,thermoelectric devices,sensors,biomedical materials,and spintronic devices.Finally,this review con-cludes with a few perspectives and an outlook for quickly expanding the appli-cation scope Ge-based 2D materials based on recent developments.
