The charge-storage characteristics of charge trapping memory devices containing different sizes of Au nanocrystals(NCs)sandwiched by Al2O3 tunneling and blocking layers are studied.A strong impact of both Au NC size a...The charge-storage characteristics of charge trapping memory devices containing different sizes of Au nanocrystals(NCs)sandwiched by Al2O3 tunneling and blocking layers are studied.A strong impact of both Au NC size and inter-NC distance on the charge trapping capability of the devices is observed.The total surface area of Au NCs associated with Au NC size is supposed to be a key factor in the charge-storage capability,and the device with larger size of Au NCs and a suitable inter-NC distance will possess better charge trapping capability.Variable range hopping as the lateral charge loss mechanism is considered as the main reason for the decrease of the charge trapping capability when Au NCs grow and overlap neighbors.展开更多
According to first-principles calculations, it is our prediction that bilayer phosphorene（BLP） will become a quasitwo-dimensional superconductor under a certain degree of interlayer compression. A decreasing interla...According to first-principles calculations, it is our prediction that bilayer phosphorene（BLP） will become a quasitwo-dimensional superconductor under a certain degree of interlayer compression. A decreasing interlayer distance may realize the transition in the BLP from a semiconducting phase to a metallic phase. On the other hand, a severe vertical compression may make the BLP lattice become dynamically unstable. It is found that in the stable metallic phase of the BLP, interlayer phonon modes dominate the electron-phonon coupling λ. The obtained λ can be greater than 1 and the superconducting temperature T_c can be higher than 10 K.展开更多
The carrier mobility of two-dimensional tetragonal carbon allotrope （T-CA） from porous graphene is investigated by first-principles calculations. T-CA can be constructed from divacancy and Stone-Thrower--Wales defec...The carrier mobility of two-dimensional tetragonal carbon allotrope （T-CA） from porous graphene is investigated by first-principles calculations. T-CA can be constructed from divacancy and Stone-Thrower--Wales defects from graphene. T-CA is a direct semiconductor with a band gap of 0.4 eV at F point. T-CA possesses a high carrier mobility of the order of 104 cm2V-ls-1. As our study demonstrates, T-CA has potential applications for next-generation electronic materials.展开更多
GeTe_(4) films are deposited by using a dc magnetron sputtering technique, and its structural, thermal and electrical properties are investigated systematically. The prototypical phase-change memory cells are fabricat...GeTe_(4) films are deposited by using a dc magnetron sputtering technique, and its structural, thermal and electrical properties are investigated systematically. The prototypical phase-change memory cells are fabricated by using a focused ion beam and magnetron sputtering techniques. Compared with Ge_(2)Sb_(2)Te_(5), the GeTe_(4) film exhibits a higher crystallization temperature (235℃), better data retention of ten years at 129℃, and larger activation energy (2.94 eV). GeTe4 phase change memory cells with an effective diameter of 1 μm show proper switching speed, low power consumption, and good resistance contrast. The Set and Reset operations are achieved by using a 200-ns 2.0-V pulse and a 30-ns 3.0-V pulse, respectively. The dynamic switching ratio between the OFF and ON states is larger than 1×10^(4).展开更多
A memory device Si/Al2O3/Al2O3-Cu2O/Al2O3/Pt is fabricated by using atomic layer deposition and r^magnetron sputtering techniques. The memory device including the composite of Al2O3 and Cu2O as the charge storage laye...A memory device Si/Al2O3/Al2O3-Cu2O/Al2O3/Pt is fabricated by using atomic layer deposition and r^magnetron sputtering techniques. The memory device including the composite of Al2O3 and Cu2O as the charge storage layer shows a distinguished charge trapping capability. At a working voltage of ±11 V a memory window of 9.22 V is obtained. The x-ray photoelectron spectroscopic study shows a shoulder from Cu2＋ ions around the peak of Cu1＋ ions. It is suggested that the charge-trapping mechanism should be attributed to the defect states formed by the inter-diffusion at the interface of two oxides.展开更多
We study the electronic properties of CuAlO2 doped with S by the first principles calculations and find that the band gap of CuAlO2 is reduced after the doping.At the same time,the effective masses are also reduced an...We study the electronic properties of CuAlO2 doped with S by the first principles calculations and find that the band gap of CuAlO2 is reduced after the doping.At the same time,the effective masses are also reduced and the density of states could cross the Fermi level.These results show that the conductivity of CuAlO2 could be enhanced by doping the impurities of S,which needs to be further studied.展开更多
The electric-pulse-induced resistive switching effect is studied for Tio.s5Cro.15Ox （TCO） films grown on Ir-Si substrates by pulsed laser deposition. Such a TCO device exhibits bipolar switching behaviour with an el...The electric-pulse-induced resistive switching effect is studied for Tio.s5Cro.15Ox （TCO） films grown on Ir-Si substrates by pulsed laser deposition. Such a TCO device exhibits bipolar switching behaviour with an electric-pulse- induced resistance ratio as large as about 1000% and threshold voltages smaller than 2 V. The resistive switching characteristics may be understood by resistance changes of a Schottky junction composed of a metal and an n-type semiconductor, and its nonvolatility is attributed to the movement of oxygen vacancies near the interface.展开更多
We investigate both experimentally and numerically a complex structure, where ＇face-to-face＇ Helmholtz resonance cavities （HRCs） are introduced to construct a one-dimensional acoustic grating. In this system, pair...We investigate both experimentally and numerically a complex structure, where ＇face-to-face＇ Helmholtz resonance cavities （HRCs） are introduced to construct a one-dimensional acoustic grating. In this system, pairs of HRCs can intensely couple with each other in two forms： a bonding state and an anti-bonding state, analogous to the character of hydrogen molecule with two atoms due to the interference of wave functions of sound among the acoustic local-resonating structures. The bonding state is a ＇bright＇ state that interferes with the Fabry-Pbrot resonance mode, thereby causing this state to break up into two modes as the splitting of the extraordinary acoustic transmission peak. On the contrary, the anti-bonding state is a ＇dark＇ state in which the resonance mode remains entirely localized within the HRCs, and has no contribution to the acoustic transmission.展开更多
Design of nonmagnetic optical isolators integrated with silicon waveguides is important for rapidly growing sil-icon photonics in optical communications.We introduce a silicon waveguide consisting of an array of compl...Design of nonmagnetic optical isolators integrated with silicon waveguides is important for rapidly growing sil-icon photonics in optical communications.We introduce a silicon waveguide consisting of an array of complex sinusoidal-shaped structures that create the designed time-dependent modulation of refractive indices.These time-dependent sinusoidal-shaped structures are engineered to have in-phase mode conversion only in one direc-tion,thus leading to asymmetric optical mode conversion in the silicon waveguide and one-way light transmission with high contrast ratios,confirmed by numerically simulated field maps and calculated transmission at the wavelength of 1550nm.Our design may offer another practical design to the compact chip-scale optical isolators in silicon waveguides.展开更多
Node line band-touchings protected by mirror symmetry(named as m-NLs),the product of inversion and time reversal symmetry S=PT(named as s-NLs),or nonsymmorphic symmetry are nontrivial topological objects of topologica...Node line band-touchings protected by mirror symmetry(named as m-NLs),the product of inversion and time reversal symmetry S=PT(named as s-NLs),or nonsymmorphic symmetry are nontrivial topological objects of topological semimetals in the Brillouin Zone.In this work,we screened a family of MgSrSi-type crystals using first principles calculations,and discovered that more than 70 members are node-line semimetals.A new type of multi-loop structure was found in AsRhTi that a s-NL touches robustly with a m-NL at some“nexus point”,and in the meanwhile a second m-NL crosses with the s-NL to form a Hopf-link.Unlike the previously proposed Hopf-link formed by two s-NLs or two m-NLs,a Hopf-link formed by a s-NL and a m-NL requires a minimal three-band model to characterize its essential electronic structure.The associated topological surface states on different surfaces of AsRhTi crystal were also obtained.Even more complicated and exotic multi-loop structure of NLs were predicted in AsFeNb and PNiNb.Our work may shed light on search for exotic multi-loop node-line semimetals in real materials.展开更多
The field of topological photonic crystals has attracted growing interest since the inception of optical analog of quantum Hall effect proposed in 2008.Photonic band structures embraced topological phases of matter,ha...The field of topological photonic crystals has attracted growing interest since the inception of optical analog of quantum Hall effect proposed in 2008.Photonic band structures embraced topological phases of matter,have spawned a novel platform for studying topological phase transitions and designing topological optical devices.Here,we present a brief review of topological photonic crystals based on different material platforms,including all-dielectric systems,metallic materials,optical resonators,coupled waveguide systems,and other platforms.Furthermore,this review summarizes recent progress on topological photonic crystals,such as higherorder topological photonic crystals,non-Hermitian photonic crystals,and nonlinear photonic crystals.These studies indicate that topological photonic crystals as versatile platforms have enormous potential applications in maneuvering the flow of light.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 61176124the National Basic Research Program of China under Grant No 2010CB934201the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘The charge-storage characteristics of charge trapping memory devices containing different sizes of Au nanocrystals(NCs)sandwiched by Al2O3 tunneling and blocking layers are studied.A strong impact of both Au NC size and inter-NC distance on the charge trapping capability of the devices is observed.The total surface area of Au NCs associated with Au NC size is supposed to be a key factor in the charge-storage capability,and the device with larger size of Au NCs and a suitable inter-NC distance will possess better charge trapping capability.Variable range hopping as the lateral charge loss mechanism is considered as the main reason for the decrease of the charge trapping capability when Au NCs grow and overlap neighbors.
基金Project supported by the State Key Program for Basic Researches of China(Grant No.2014CB921103)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20141441 and BK2010012)
文摘According to first-principles calculations, it is our prediction that bilayer phosphorene（BLP） will become a quasitwo-dimensional superconductor under a certain degree of interlayer compression. A decreasing interlayer distance may realize the transition in the BLP from a semiconducting phase to a metallic phase. On the other hand, a severe vertical compression may make the BLP lattice become dynamically unstable. It is found that in the stable metallic phase of the BLP, interlayer phonon modes dominate the electron-phonon coupling λ. The obtained λ can be greater than 1 and the superconducting temperature T_c can be higher than 10 K.
基金Supported by the Fundamental Research Funds for the Central Universitiesthe Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe National Natural Science Foundation of China under Grant No 11204123
文摘The carrier mobility of two-dimensional tetragonal carbon allotrope （T-CA） from porous graphene is investigated by first-principles calculations. T-CA can be constructed from divacancy and Stone-Thrower--Wales defects from graphene. T-CA is a direct semiconductor with a band gap of 0.4 eV at F point. T-CA possesses a high carrier mobility of the order of 104 cm2V-ls-1. As our study demonstrates, T-CA has potential applications for next-generation electronic materials.
基金the National Natural Science Foundation of China under Grant Nos 51072078 and 61076008the National Basic Research Program of China under Grant No 2010CB630704the College Graduate Research and Innovation Project of Jiangsu Province under Grant No CXZZ12_0050.
文摘GeTe_(4) films are deposited by using a dc magnetron sputtering technique, and its structural, thermal and electrical properties are investigated systematically. The prototypical phase-change memory cells are fabricated by using a focused ion beam and magnetron sputtering techniques. Compared with Ge_(2)Sb_(2)Te_(5), the GeTe_(4) film exhibits a higher crystallization temperature (235℃), better data retention of ten years at 129℃, and larger activation energy (2.94 eV). GeTe4 phase change memory cells with an effective diameter of 1 μm show proper switching speed, low power consumption, and good resistance contrast. The Set and Reset operations are achieved by using a 200-ns 2.0-V pulse and a 30-ns 3.0-V pulse, respectively. The dynamic switching ratio between the OFF and ON states is larger than 1×10^(4).
基金Supported by the National Natural Science Foundation of China under Grand Nos 61176124 and 11204123, and the National Basic Research Program of China under Grant No 2010CB934201.
文摘A memory device Si/Al2O3/Al2O3-Cu2O/Al2O3/Pt is fabricated by using atomic layer deposition and r^magnetron sputtering techniques. The memory device including the composite of Al2O3 and Cu2O as the charge storage layer shows a distinguished charge trapping capability. At a working voltage of ±11 V a memory window of 9.22 V is obtained. The x-ray photoelectron spectroscopic study shows a shoulder from Cu2＋ ions around the peak of Cu1＋ ions. It is suggested that the charge-trapping mechanism should be attributed to the defect states formed by the inter-diffusion at the interface of two oxides.
基金supported by the National Laboratory of Solid State Microstructures (Grant No. 2010YJ07)
文摘We study the electronic properties of CuAlO2 doped with S by the first principles calculations and find that the band gap of CuAlO2 is reduced after the doping.At the same time,the effective masses are also reduced and the density of states could cross the Fermi level.These results show that the conductivity of CuAlO2 could be enhanced by doping the impurities of S,which needs to be further studied.
基金Project supported by NASA,the State of Texas through the Center for Advanced Materials,Sharp Laboratories of America,Semiconductor Research Corporation,the R.A.Welch Foundation (Grant No.#E-632)the National Natural Science Foundation of China (Grant No.11074109)+2 种基金the Natural Science Foundation of Jiangsu Province of China (Grant No.SBK200920627)the National Basic Research Program of China (Grant No.2010CB923404)the National "Climbing" Program of China (Grant No.91021003)
文摘The electric-pulse-induced resistive switching effect is studied for Tio.s5Cro.15Ox （TCO） films grown on Ir-Si substrates by pulsed laser deposition. Such a TCO device exhibits bipolar switching behaviour with an electric-pulse- induced resistance ratio as large as about 1000% and threshold voltages smaller than 2 V. The resistive switching characteristics may be understood by resistance changes of a Schottky junction composed of a metal and an n-type semiconductor, and its nonvolatility is attributed to the movement of oxygen vacancies near the interface.
基金Supported by the National Basic Research Program of China under Grant Nos 2012CB921503,2013CB632904 and 2013CB632702the National Natural Science Foundation of China under Grant No 1134006+2 种基金the Natural Science Foundation of Jiangsu Province under Grant No BK20140019the Project Funded by the Priority Academic Program Development of Jiangsu Higher Educationthe China Postdoctoral Science Foundation under Grant Nos 2012M511249 and 2013T60521
文摘We investigate both experimentally and numerically a complex structure, where ＇face-to-face＇ Helmholtz resonance cavities （HRCs） are introduced to construct a one-dimensional acoustic grating. In this system, pairs of HRCs can intensely couple with each other in two forms： a bonding state and an anti-bonding state, analogous to the character of hydrogen molecule with two atoms due to the interference of wave functions of sound among the acoustic local-resonating structures. The bonding state is a ＇bright＇ state that interferes with the Fabry-Pbrot resonance mode, thereby causing this state to break up into two modes as the splitting of the extraordinary acoustic transmission peak. On the contrary, the anti-bonding state is a ＇dark＇ state in which the resonance mode remains entirely localized within the HRCs, and has no contribution to the acoustic transmission.
基金Supported by the National Basic Research of China under Grant Nos 2012CB921503 and 2013CB632702the National Natural Science Foundation of China under Grant No 11134006the Priority Academic Program Development of Jiangsu Higher Education and FANEDD of China.
文摘Design of nonmagnetic optical isolators integrated with silicon waveguides is important for rapidly growing sil-icon photonics in optical communications.We introduce a silicon waveguide consisting of an array of complex sinusoidal-shaped structures that create the designed time-dependent modulation of refractive indices.These time-dependent sinusoidal-shaped structures are engineered to have in-phase mode conversion only in one direc-tion,thus leading to asymmetric optical mode conversion in the silicon waveguide and one-way light transmission with high contrast ratios,confirmed by numerically simulated field maps and calculated transmission at the wavelength of 1550nm.Our design may offer another practical design to the compact chip-scale optical isolators in silicon waveguides.
基金The work is supported by National Natural Science Foundation of China(NSFC)(Grants No.11574215,No.11575116,No.11274359,and No.11422428)H.M.W is also supported by the National 973 program of China(Grants No.2018YFA0305700 and No.2013CB921700)the“Strategic Priority Research Program(B)”of the Chinese Academy of Sciences(Grant No.XDB07020100).
文摘Node line band-touchings protected by mirror symmetry(named as m-NLs),the product of inversion and time reversal symmetry S=PT(named as s-NLs),or nonsymmorphic symmetry are nontrivial topological objects of topological semimetals in the Brillouin Zone.In this work,we screened a family of MgSrSi-type crystals using first principles calculations,and discovered that more than 70 members are node-line semimetals.A new type of multi-loop structure was found in AsRhTi that a s-NL touches robustly with a m-NL at some“nexus point”,and in the meanwhile a second m-NL crosses with the s-NL to form a Hopf-link.Unlike the previously proposed Hopf-link formed by two s-NLs or two m-NLs,a Hopf-link formed by a s-NL and a m-NL requires a minimal three-band model to characterize its essential electronic structure.The associated topological surface states on different surfaces of AsRhTi crystal were also obtained.Even more complicated and exotic multi-loop structure of NLs were predicted in AsFeNb and PNiNb.Our work may shed light on search for exotic multi-loop node-line semimetals in real materials.
基金supported by the National Key R&D Program of China(Nos.2018YFA0306200,and 2017YFA0303702)the National Natural Science Foundation of China(Grant Nos.11625418,51732006,and 11890700)as well as the Academic Program Development of Jiangsu Higher Education(PAPD).
文摘The field of topological photonic crystals has attracted growing interest since the inception of optical analog of quantum Hall effect proposed in 2008.Photonic band structures embraced topological phases of matter,have spawned a novel platform for studying topological phase transitions and designing topological optical devices.Here,we present a brief review of topological photonic crystals based on different material platforms,including all-dielectric systems,metallic materials,optical resonators,coupled waveguide systems,and other platforms.Furthermore,this review summarizes recent progress on topological photonic crystals,such as higherorder topological photonic crystals,non-Hermitian photonic crystals,and nonlinear photonic crystals.These studies indicate that topological photonic crystals as versatile platforms have enormous potential applications in maneuvering the flow of light.
基金supported by the National Natural Science Foundation of China (21825102,22075014 and 22001014)the Fundamental Research Funds for the Central Universities,China(06500162 and 06500145)。
