Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle...Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.展开更多
Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability...Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.展开更多
Mo,as a dopant,is doped into SbTe to improve its thermal stability.It is shown in this paper that the Mo-doped Sb_(2)Te_(3)(Mo_(0.26)Sb_(2)Te_(3),MST)material possesses phase change memory(PCM)applications.MST has bet...Mo,as a dopant,is doped into SbTe to improve its thermal stability.It is shown in this paper that the Mo-doped Sb_(2)Te_(3)(Mo_(0.26)Sb_(2)Te_(3),MST)material possesses phase change memory(PCM)applications.MST has better thermal stability than Sb_(2)Te_(3)(ST)and will crystallize only when the annealing temperature is higher than 250℃.With the good thermal stability,MST-based PCM cells have a fast crystallization time of 6 ns.Furthermore,endurance up to 4×10^(5) cycles with a resistance ratio of more than one order of magnitude makes MST a promising candidate for PCM applications.展开更多
High-quality SbTenanostructures are synthesized by a simple hydrothermal method. The morphologies of the nanostructures change from hexagonal nanoplates to nanorods with the extension of growth time. Secondary nucleat...High-quality SbTenanostructures are synthesized by a simple hydrothermal method. The morphologies of the nanostructures change from hexagonal nanoplates to nanorods with the extension of growth time. Secondary nucleation is the dominant factor responsible for the change of the morphologies. Structural analyses indicate that all the obtained nanostructures are well crystallized. IR-active phonons are mainly observed in the Raman spectra of the nanoplates and nanorods. The slight deviations are observed in the Raman modes between the nanoplates and nanorods, which could originate from confinement effect in the nanostructures.展开更多
Bi_(2)Te_(3)-based alloys are known to have outstanding thermoelectric properties.Although structure–property relations have been studied,still,detailed analysis of the atomic and nano-scale structure of Bi_(2)Te_(3)...Bi_(2)Te_(3)-based alloys are known to have outstanding thermoelectric properties.Although structure–property relations have been studied,still,detailed analysis of the atomic and nano-scale structure of Bi_(2)Te_(3)thin film in relation to their thermoelectric properties remains poorly explored.Herein,highly-textured(HT)and single-crystal-like(SCL)Bi_(2)Te_(3)films have been grown using pulsed laser deposition(PLD)on Si wafer covered with(native or thermal)SiOx and mica substrates.All films are highly textured with c-axis out-of-plane,but the in-plane orientation is random for the films grown on oxide and single-crystal-like for the ones grown on mica.The power factor of the film on thermal oxide is about four times higher(56.8μW·cm^(−1)·K^(−2))than that of the film on mica(12.8μW·cm^(−1)·K^(−2)),which is comparable to the one of the polycrystalline ingot at room temperature(RT).Reduced electron scattering in the textured thin films results in high electrical conductivity,where the SCL film shows the highest conductivity.However,its Seebeck coefficient shows a low value.The measured properties are correlated with the atomic structure details unveiled by scanning transmission electron microscopy.For instance,the high concentration of stacking defects observed in the HT film is considered responsible for the increase of Seebeck coefficient compared to the SCL film.This study demonstrates the influence of nanoscale structural effects on thermoelectric properties,which sheds light on tailoring thermoelectric thin films towards high performance.展开更多
Bi_(2)Te_(3)-based materials are not only the most important and widely used room temperature thermoelectric(TE)materials but are also canonical examples of topological insulators in which the topological surface stat...Bi_(2)Te_(3)-based materials are not only the most important and widely used room temperature thermoelectric(TE)materials but are also canonical examples of topological insulators in which the topological surface states are protected by the time-reversal symmetry.High-performance thin films based on Bi_(2)Te_(3)- have attracted worldwide attention during the past two decades due primarily to their outstanding TE performance as highly efficient TE coolers and as miniature and flexible TE power generators for a variety of electronic devices.Moreover,intriguing topological phenomena,such as the quantum anomalous Hall effect and topological superconductivity discovered in Bi_(2)Te_(3)-based thin films and heterostructures,have shaped research directions in the field of condensed matter physics.In Bi_(2)Te_(3)-based films and heterostructures,delicate control of the carrier transport,film composition,and microstructure are prerequisites for successful device operations as well as for experimental verification of exotic topological phenomena.This review summarizes the recent progress made in atomic defect engineering,carrier tuning,and band engineering down to a nanoscale regime and how it relates to the growth and fabrication of high-quality Bi_(2)Te_(3)-based films.The review also briefly discusses the physical insight into the exciting field of topological phenomena that were so dramatically realized in Bi_(2)Te_(3)-and Bi_(2)Se_(3)‐based structures.It is expected that Bi_(2)Te_(3)-based thin films and heterostructures will play an ever more prominent role as flexible TE devices collecting and converting low-level(body)heat into electricity for numerous electronic applications.It is also likely that such films will continue to be a remarkable platform for the realization of novel topological phenomena.展开更多
Antimony selenide(Sb_(2)Se_(3))has drawn tremendous research attentions in recent years as an environment-friendly and cost-efficient photovoltaic material.However,the intrinsic low carrier density and electrical cond...Antimony selenide(Sb_(2)Se_(3))has drawn tremendous research attentions in recent years as an environment-friendly and cost-efficient photovoltaic material.However,the intrinsic low carrier density and electrical conductivity limited its scope of applications.In this work,an effective ion doping strategy was implemented to improve the electrical and photoelectrical performances of Sb_(2)Se_(3) thin films.The Sn-doped and I-doped Sb_(2)Se_(3) thin films with controllable chemical composition can be prepared by magnetron sputtering combined with post-selenization treatment based on homemade plasma sintered targets.As a result,the Sn-doped Sb_(2)Se_(3) thin film exhibited a great increase in carrier density by several orders of magnitude,by contrast,a less increase with one order of magnitude was achieved for the Idoped Sb_(2)Se_(3) thin film.Additionally,such cation or anion doping could simultaneously modify the conduction type of Sb_(2)Se_(3),enabling the first fabrication of a substrate structured Sb_(2)Se_(3)-based quasihomojunction thin film solar cell with configuration of Mo/Sb_(2)Se_(3)-Sn/Sb_(2)Se_(3)-I/ITO/Ag.The obtained power conversion efficiency exceeding 2%undoubtedly demonstrated its attractive photovoltaic application potential and further investigation necessity.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62074036,61674038,and 11574302)the Foreign Cooperation Project of Fujian Province,China(Grant No.2023I0005)+2 种基金the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(Grant No.KF202108)the National Key Research and Development Program of China(Grant No.2016YFB0402303)the Foundation of Fujian Provincial Department of Industry and Information Technology of China(Grant No.82318075)。
文摘Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62205231 and 22002102)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX223271)Jiangsu Key Laboratory for Environment Functional Materials。
文摘Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFB0701703 and 2017YFA0206101)the National Natural Science Foundation of China(Grant No.61874151)the Science and Technology Council of Shanghai,China(Grant Nos.19JC1416801 and 19JC1416802).
文摘Mo,as a dopant,is doped into SbTe to improve its thermal stability.It is shown in this paper that the Mo-doped Sb_(2)Te_(3)(Mo_(0.26)Sb_(2)Te_(3),MST)material possesses phase change memory(PCM)applications.MST has better thermal stability than Sb_(2)Te_(3)(ST)and will crystallize only when the annealing temperature is higher than 250℃.With the good thermal stability,MST-based PCM cells have a fast crystallization time of 6 ns.Furthermore,endurance up to 4×10^(5) cycles with a resistance ratio of more than one order of magnitude makes MST a promising candidate for PCM applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.11104250 and 61274099)the Fund from the Science Technology Department of Zhejiang Province,China(Grant No.2012C21007)the Fund for the Zhejiang Provincial Innovation Team,China(Grant No.2011R50012)
文摘High-quality SbTenanostructures are synthesized by a simple hydrothermal method. The morphologies of the nanostructures change from hexagonal nanoplates to nanorods with the extension of growth time. Secondary nucleation is the dominant factor responsible for the change of the morphologies. Structural analyses indicate that all the obtained nanostructures are well crystallized. IR-active phonons are mainly observed in the Raman spectra of the nanoplates and nanorods. The slight deviations are observed in the Raman modes between the nanoplates and nanorods, which could originate from confinement effect in the nanostructures.
基金the China Scholarship Council,in particular for Heng Zhang’s scholarship(No.201706890019).
文摘Bi_(2)Te_(3)-based alloys are known to have outstanding thermoelectric properties.Although structure–property relations have been studied,still,detailed analysis of the atomic and nano-scale structure of Bi_(2)Te_(3)thin film in relation to their thermoelectric properties remains poorly explored.Herein,highly-textured(HT)and single-crystal-like(SCL)Bi_(2)Te_(3)films have been grown using pulsed laser deposition(PLD)on Si wafer covered with(native or thermal)SiOx and mica substrates.All films are highly textured with c-axis out-of-plane,but the in-plane orientation is random for the films grown on oxide and single-crystal-like for the ones grown on mica.The power factor of the film on thermal oxide is about four times higher(56.8μW·cm^(−1)·K^(−2))than that of the film on mica(12.8μW·cm^(−1)·K^(−2)),which is comparable to the one of the polycrystalline ingot at room temperature(RT).Reduced electron scattering in the textured thin films results in high electrical conductivity,where the SCL film shows the highest conductivity.However,its Seebeck coefficient shows a low value.The measured properties are correlated with the atomic structure details unveiled by scanning transmission electron microscopy.For instance,the high concentration of stacking defects observed in the HT film is considered responsible for the increase of Seebeck coefficient compared to the SCL film.This study demonstrates the influence of nanoscale structural effects on thermoelectric properties,which sheds light on tailoring thermoelectric thin films towards high performance.
基金This study was supported by the Natural Science Foun-dation of China(Grant No.51632006,51521001 and 91963120)National Key Research and Development Program of China(Grant No.2019YFA0704900)Wuhan Frontier Project on Applied Research Foundation(Grant No.2019010701011405).
文摘Bi_(2)Te_(3)-based materials are not only the most important and widely used room temperature thermoelectric(TE)materials but are also canonical examples of topological insulators in which the topological surface states are protected by the time-reversal symmetry.High-performance thin films based on Bi_(2)Te_(3)- have attracted worldwide attention during the past two decades due primarily to their outstanding TE performance as highly efficient TE coolers and as miniature and flexible TE power generators for a variety of electronic devices.Moreover,intriguing topological phenomena,such as the quantum anomalous Hall effect and topological superconductivity discovered in Bi_(2)Te_(3)-based thin films and heterostructures,have shaped research directions in the field of condensed matter physics.In Bi_(2)Te_(3)-based films and heterostructures,delicate control of the carrier transport,film composition,and microstructure are prerequisites for successful device operations as well as for experimental verification of exotic topological phenomena.This review summarizes the recent progress made in atomic defect engineering,carrier tuning,and band engineering down to a nanoscale regime and how it relates to the growth and fabrication of high-quality Bi_(2)Te_(3)-based films.The review also briefly discusses the physical insight into the exciting field of topological phenomena that were so dramatically realized in Bi_(2)Te_(3)-and Bi_(2)Se_(3)‐based structures.It is expected that Bi_(2)Te_(3)-based thin films and heterostructures will play an ever more prominent role as flexible TE devices collecting and converting low-level(body)heat into electricity for numerous electronic applications.It is also likely that such films will continue to be a remarkable platform for the realization of novel topological phenomena.
基金supported by Natural Science Foundation of Guangdong Province(2020A1515010805)ChinaNational Natural Science Foundation of China(No.62074102)+1 种基金Key Project of Department of Education of Guangdong Province(No.2018KZDXM059)ChinaScience and Technology plan project of Shenzhen(JCYJ20190808153409238)China.
文摘Antimony selenide(Sb_(2)Se_(3))has drawn tremendous research attentions in recent years as an environment-friendly and cost-efficient photovoltaic material.However,the intrinsic low carrier density and electrical conductivity limited its scope of applications.In this work,an effective ion doping strategy was implemented to improve the electrical and photoelectrical performances of Sb_(2)Se_(3) thin films.The Sn-doped and I-doped Sb_(2)Se_(3) thin films with controllable chemical composition can be prepared by magnetron sputtering combined with post-selenization treatment based on homemade plasma sintered targets.As a result,the Sn-doped Sb_(2)Se_(3) thin film exhibited a great increase in carrier density by several orders of magnitude,by contrast,a less increase with one order of magnitude was achieved for the Idoped Sb_(2)Se_(3) thin film.Additionally,such cation or anion doping could simultaneously modify the conduction type of Sb_(2)Se_(3),enabling the first fabrication of a substrate structured Sb_(2)Se_(3)-based quasihomojunction thin film solar cell with configuration of Mo/Sb_(2)Se_(3)-Sn/Sb_(2)Se_(3)-I/ITO/Ag.The obtained power conversion efficiency exceeding 2%undoubtedly demonstrated its attractive photovoltaic application potential and further investigation necessity.
