Cu2ZnSn(S,Se)4(CZTSSe)solar cells have resource distribution and economic advantages.The main cause of their low efficiency is carrier loss resulting from recombination of photo-generated electron and hole.To overcome...Cu2ZnSn(S,Se)4(CZTSSe)solar cells have resource distribution and economic advantages.The main cause of their low efficiency is carrier loss resulting from recombination of photo-generated electron and hole.To overcome this,it is important to understand their electron-hole behavior characteristics.To determine the carrier separation characteristics,we measured the surface potential and the local current in terms of the absorber depth.The elemental variation in the intragrains(IGs)and at the grain boundaries(GBs)caused a band edge shift and bandgap(Eg)change.At the absorber surface and subsurface,an upward Ec and Ev band bending structure was observed at the GBs,and the carrier separation was improved.At the absorber center,both upward Ec and Ev and downward Ec-upward Ev band bending structures were observed at the GBs,and the carrier separation was degraded.To improve the carrier separation and suppress carrier recombination,an upward Ec and Ev band bending structure at the GBs is desirable.展开更多
By calculating the energy distribution of electrons reaching the photocathode surface and solving the Schrodinger equation that describes the behavior of an electron tunneling through the surface potential barrier,we ...By calculating the energy distribution of electrons reaching the photocathode surface and solving the Schrodinger equation that describes the behavior of an electron tunneling through the surface potential barrier,we obtain an equation to calculate the emitted electron energy distribution of transmission-mode NEA GaAs photocathodes. Accord- ing to the equation,we study the effect of cathode surface potential barrier on the electron energy distribution and find a significant effect of the barrier-Ⅰ thickness or end height,especially the thickness,on the quantum efficiency of the cath- ode. Barrier Ⅱ has an effect on the electron energy spread, and an increase in the vacuum level will lead to a narrower electron energy spread while sacrificing a certain amount of cathode quantum efficiency. The equation is also used to fit the measured electron energy distribution curve of the transmission-mode cathode and the parameters of the surface barri- er are obtained from the fitting. The theoretical curve is in good agreement with the experimental curve.展开更多
A continuous and analytical surface potential model for SOI LDMOS, which accounts for automatic transitions between fully and partially-depleted statuses,is presented. The surface potential equation of the SOI de- vic...A continuous and analytical surface potential model for SOI LDMOS, which accounts for automatic transitions between fully and partially-depleted statuses,is presented. The surface potential equation of the SOI de- vice is solved by using the PSP′s accurate algorithm of surface potential,and the front and back surface potentials are obtained analytically as a function of gate and drain voltage. The formulations of inversion charge and body charge under the fully-depleted state have been modified. The continuous and analytical DC model for SOl LD- MOS is given based on PSP. The comparisons between simulation and measurements indicate that this model can predict the DC characteristics of SOI LDMOS accurately.展开更多
A refinement of an analytical approximation of the surface potential in MOSFETs is proposed by introducing a high-order term. As compared to the conventional treatment with accuracy between 1nV and 0. 03mV in the case...A refinement of an analytical approximation of the surface potential in MOSFETs is proposed by introducing a high-order term. As compared to the conventional treatment with accuracy between 1nV and 0. 03mV in the cases with an oxide thickness tox = 1 ～ 10nm and substrate doping concentration Na = 1015 ～ 1018 cm-3 , this method yields an accuracy within about 1pV in all cases. This is comparable to numerical simulations, but does not require trading off much computation efficiency. More importantly, the spikes in the error curve associated with the traditional treatment are eliminated.展开更多
As a fundamental surface property of two-dimensional(2 D)materials,surface potential is critical for their emerging electronic applications and essential for van der Waals heterostructure engineering.Here,we report th...As a fundamental surface property of two-dimensional(2 D)materials,surface potential is critical for their emerging electronic applications and essential for van der Waals heterostructure engineering.Here,we report the surface potential of few-layer InSe.The effect of layer count,light intensity and different deposited substrates is considered.Few-layer InSe flakes were exfoliated from bulk InSe crystals on Si/SiO_(2)with 300-nm-thick thermal oxide and Si/SiO_(2)with 300-nm-thick thermal oxide and prefabricated micro-wells with 3μm in diameter.The samples were measured by Kelvin probe force microscopy and tuned by an integrated 405-nm(3.06 eV)laser.Based on the work function of SiO_(2)(5.00 eV),the work functions of supported and suspended InSe are determined.These results show that the work function of InSe decreases with the increase in the layer count of both supported InSe and suspended InSe.Besides,by introducing a tunable laser light,the influence of light intensity on surface potential of supported InSe was studied.The surface potential(SP)and surface potential shift between light and dark states(ASP=SP_(lignt)-SP_(dark))of supported InSe were measured and determined.These results present that the surface potential of supported InSe decreases with the increase in the light intensity and also decreases with the increase in the layer count.This is evident that light excites electrons,resulting in decreased surface potential,and the amount of electrons excited is correlated with light intensity.Meanwhile,⊿SP between light and dark states decreases with the increase in the layer count,which suggests that the influence of light illumination decreases with the increase in the layer count of few-layer InSe flakes.展开更多
The influences of interannual surface potential vorticity forcing over the Tibetan Plateau(TP)on East Asian summer rainfall(EASR)and upper-level circulation are explored in this study.The results show that the interan...The influences of interannual surface potential vorticity forcing over the Tibetan Plateau(TP)on East Asian summer rainfall(EASR)and upper-level circulation are explored in this study.The results show that the interannual EASR and associated circulations are closely related to the surface potential vorticity negative uniform leading mode(PVNUM)over the TP.When the PVNUM is in the positive phase,more rainfall occurs in the Yangtze River valley,South Korea,Japan,and part of northern China,less rainfall occurs in southern China,and vice versa.A possible mechanism by which PVNUM affects EASR is proposed.Unstable air induced by the positive phase of PVNUM could stimulate significant upward motion and a lower-level anomalous cyclone over the TP.As a result,a dipole heating mode with anomalous cooling over the southwestern TP and anomalous heating over the southeastern TP is generated.Sensitivity experiment results regarding this dipole heating mode indicate that anomalous cooling over the southwestern TP leads to local and northeastern Asian negative height anomalies,while anomalous heating over the southeastern TP leads to local positive height anomalies.These results greatly resemble the realistic circulation pattern associated with EASR.Further analysis indicates that the anomalous water vapor transport associated with this anomalous circulation pattern is responsible for the anomalous EASR.Consequently,changes in surface potential vorticity forcing over the TP can induce changes in EASR.展开更多
Surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson–...Surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson–Boltzmann theory with the consideration of the dielectric decrement in mixed electrolyte. The analytical relationships between surface potential and charge density are derived in different mixed electrolytes with monovalent and bivalent ions. The dielectric decrease on the charged surface strongly affects the surface potential at a high charge density with different ion strengths and concentration ratios of counter-ions. The surface potential based on the Gouy–Chapman model is underestimated because of the dielectric decrement on the surface. The diffuse layer can be regarded as a continuous uniform medium only when the surface charge density is lower than 0.3 C·m-2. However, the surface charge densities of many materials in practical applications are higher than 0.3 C·m-2. The new model for the estimation of surface potential can return to the results obtained based on the Gouy–Chapman model at a low charge density. Therefore, it is implied that the established model that considers the dielectric decrement is valid and widely applicable.展开更多
Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor(H-TFET). This model accounts for both the effec...Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor(H-TFET). This model accounts for both the effects of source depletion and inversion charge, which are the key factors influencing the charge, capacitance and current in H-TFET. The accuracy of the model is validated against TCAD simulation and is greatly improved in comparison with the conventional model based on Maxwell–Boltzmann approximation. Furthermore, the dependences of the surface potential and electric field on biases are well predicted and thoroughly analyzed.展开更多
The improvement of the characteristics of grooved-gate MOSFETs compared to the planar devices is attributed to the corner effect of the surface potential along the channel. In this paper we propose an analytical model...The improvement of the characteristics of grooved-gate MOSFETs compared to the planar devices is attributed to the corner effect of the surface potential along the channel. In this paper we propose an analytical model of the surface potential distribution based on the solution of two-dimensional Poisson equation in cylindrical coordinates utilizing the cylinder approximation and the structure parameters such as the concave corner θ0. The relationship between the minimum surface potential and the structure parameters is theoretically analysed. Results confirm that the bigger the concave corner, the more obvious the corner effect. The corner effect increases the threshold voltage of the grooved-gate MOSFETs, so the better is the short channel effect （SCE） immunity.展开更多
Simultaneous measurements of surface pressure and surface potential and scanning tunneling microscopy study for N-docosylpyridinium- TCNQ monolayer were carried out.These methods allow us to get more informations on p...Simultaneous measurements of surface pressure and surface potential and scanning tunneling microscopy study for N-docosylpyridinium- TCNQ monolayer were carried out.These methods allow us to get more informations on properties of the monolayer.The molecules at the final stage of compression are really in compact stack although a voluminous hydrophilic head exists in the molecule.展开更多
In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Bolt...In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.展开更多
The immobilization of biomaterials on a carrier is the first step for many different applications in life science and medicine. The usage of surface-near electrostatic forces is one possible approach to guide the char...The immobilization of biomaterials on a carrier is the first step for many different applications in life science and medicine. The usage of surface-near electrostatic forces is one possible approach to guide the charged biomaterials to a specific location on the carrier. In this study, we investigate the effect of intrinsic defects on the surface potential of silicon carriers in the dark and under illumination by means of Kelvin probe force microscopy. The intrinsic defects were introduced into the carrier by local, stripe-patterned ion implantation of silicon ions with a fluence of 3 × 10<sup>13</sup> Si ions/cm<sup>2</sup> and 3 × 10<sup>15</sup> Si ions/cm<sup>2</sup> into a p-type silicon wafer with a dopant concentration of 9 × 10<sup>15</sup> B/cm<sup>3</sup>. The patterned implantation allows a direct comparison between the surface potential of the silicon host against the surface potential of implanted stripes. The depth of the implanted silicon ions in the target and the concentration of displaced silicon atoms was simulated using the Stopping and Range of Ions in Matter (SRIM) software. The low fluence implantation shows a negligible effect on the measured Kelvin bias in the dark, whereas the large fluence implantation leads to an increased Kelvin bias, i.e. to a smaller surface work function according to the contact potential difference model. Illumination causes a reduced surface band bending and surface potential in the non-implanted regions. The change of the Kelvin bias in the implanted regions under illumination provides insight into the mobility and lifetime of photo-generated electron-hole pairs. Finally, the effect of annealing on the intrinsic defect density is discussed and compared with atomic force microscopy measurements on the 2<sup>nd</sup> harmonic. In addition, by using the Baumgart, Helm, Schmidt interpretation of the measured Kelvin bias, the dopant concentration after implantation is estimated.展开更多
The effect of barrier material on AC breakdown voltages of a hybrid gas-solid insulation is investigated by examining the behavior of electrostatic potential on barrier surfaces.Breakdown characteristics of air-insula...The effect of barrier material on AC breakdown voltages of a hybrid gas-solid insulation is investigated by examining the behavior of electrostatic potential on barrier surfaces.Breakdown characteristics of air-insulated gaps with barriers made of three different polymeric materials are experimentally investigated.Further,measurements of surface potential on the barriers are performed and the results are utilized to obtain surface charge dynamic characteristics for the three polymeric materials and extract their electric conductivities,charge carrier mobilities,and trap energy distributions.It is found that the material with the lowest initial surface potential and fastest decay rate exhibits the highest bulk conductivity and carriers'mobility,as well as the lowest trap energy level.These properties provide the highest increase in AC breakdown voltages compared with pure air.It is concluded that materials where the accumulation of charges in the bulk is inhibited and decay of surface charges is facilitated,allow for higher operating voltages of AC hybrid gas-solid insulation systems.The mechanism of the effect of barrier material on AC breakdown voltage is discussed.展开更多
Potential energy surfaces(PESs), vibrational frequencies, and infrared spectra are calculated for NF_(3)^(+) using ab initio calculations, based on UCCSD(T)/cc-p VTZ combined with vibrational configuration interaction...Potential energy surfaces(PESs), vibrational frequencies, and infrared spectra are calculated for NF_(3)^(+) using ab initio calculations, based on UCCSD(T)/cc-p VTZ combined with vibrational configuration interaction(VCI). Based on an iterative algorithm, the surfaces(SURF) program adds automatic points to the lattice representation of the potential function, the one-dimensional and two-dimensional PESs are calculated after reaching a convergence threshold, finally the smooth image of the potential energy surface is fitted. The PESs accurately account for the interaction between the different modes, with the mode q_(6) symmetrical stretching vibrations having the greatest effect on the potential energy change of the whole system throughout the potential energy surface shift. The anharmonic frequencies are obtained when the VCI matrix is diagonalized. Fundamental frequencies, overtones, and combination bands of NF_(3)^(+) are calculated, which generate the degenerate phenomenon between their frequencies. Finally, the calculated anharmonic frequency is used to plot the infrared spectra.Modal antisymmetric stretching ν_(5) and symmetric stretching ν_(6) exhibit a phenomenon of large-intensity borrowing. This study can provide data to support the characterization in the laboratory.展开更多
A continuous surface potential versus voltage equation is proposed and then its solution is further discussed for a long channel intrinsic surrounding-gate（SRG） MOSFET from the accumulation to strong inversion regio...A continuous surface potential versus voltage equation is proposed and then its solution is further discussed for a long channel intrinsic surrounding-gate（SRG） MOSFET from the accumulation to strong inversion region.The original equation is derived from the exact solution of a simplified Poisson equation and then the empirical correction is performed from the mathematical condition required by the continuity of the solution,which results in a continuous surface potential versus voltage equation,allowing the surface potential and the related derivatives to be described by an analytic solution from the accumulation to strong inversion region and from linear to the saturation region accurately and continuously.From these results,the dependences of surface potential and centric potential characteristics on device geometry are analyzed and the results are also verified with the 3-D numerical simulation from the aspect of accuracy and continuity tests.展开更多
The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices.Pyroelectric current measurement is the commonly employed method,but can be complex and requires surface electro...The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices.Pyroelectric current measurement is the commonly employed method,but can be complex and requires surface electrodes.Here,we present noncontact electrostatic voltmeter measurements as a simple but highly accurate alternative,by assessing thermally-induced pyroelectric surface potential variations.We introduce a refined model that relates the surface potential variations to both the pyroelectric coefficient and the characteristic figure of merit(FOM)and test the model with square-shaped samples made from PVDF,LiNbO3 and LiTaO3.The characteristic pyroelectric coefficient for PVDF,LiNbO3 and LiTaO3 was found to be 33.4,59.9 and 208.4μC m−2 K−1,respectively.These values are in perfect agreement with literature values,and they differ by less than 2.5%from values that we have obtained with standard pyroelectric current measurements for comparison.展开更多
The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311＋ G（2d,2p） method. The potential energy surfaces （PES） along the O-N and O-O bonds have been scanned at CCSD（T）/aug-cc-pVDZ le...The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311＋ G（2d,2p） method. The potential energy surfaces （PES） along the O-N and O-O bonds have been scanned at CCSD（T）/aug-cc-pVDZ level, respectively. The calculated results show that on the O-N PES, the O3-N4 bond length of the loose transition state is 2.82A^° and the corresponding energy barrier is 25.6 kcal/mol, while on the O-O PES, the loose transition state with of O2-O3 bond length of 2.35A^° has the energy barrier of 37.4 kcal/mol. Thus the primary reaction path for peroxynitric acid is the dissociation into HO2 and NO2.展开更多
Surface potential decay of polymers for electrical insulation can help to determine the dark conductivity for spacecraft charging analysis. Due to the existence of radiation-induced conductivity, it decays fast in the...Surface potential decay of polymers for electrical insulation can help to determine the dark conductivity for spacecraft charging analysis. Due to the existence of radiation-induced conductivity, it decays fast in the first few hours after irradiation and exponentially slowly for the remaining time. The measurement of dark conductivity with this method usually takes the slow part and needs a couple of days. Integrating the Fowler formula into the deep dielectric charging equations, we obtain a new expression for the fast decay part. The experimental data of different materials, dose rates and temperatures are fitted by the new expression. Both the dark conductivity and the radiation-induced conductivity are derived and compared with other methods. The result shows a good estimation of dark conductivity and radiation-induced conductivity in high-resistivity polymers, which enables a fast measurement of dielectric conductivity within about 600 rain after irradiation.展开更多
Based on current voltage（I-Vg） and capacitance voltage（C-Vg） measurements,a reliable procedure is proposed to determine the effective surface potential Vd（Vg） in Schottky diodes.In the framework of thermionic em...Based on current voltage（I-Vg） and capacitance voltage（C-Vg） measurements,a reliable procedure is proposed to determine the effective surface potential Vd（Vg） in Schottky diodes.In the framework of thermionic emission,our analysis includes both the effect of the series resistance and the ideality factor,even voltage dependent. This technique is applied to n-type indium phosphide（n-InP） Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-Vg measurements.The study clearly shows that the depletion width and the flat band barrier height deduced from C-Vg,which are important parameters directly related to the surface potential in the semiconductor,should be estimated within our approach to obtain more reliable information.展开更多
Nanodevices based on the single nanoparticle represent innovative and promising technology,which could satisfy the increasing requirements of high accuracy,low energy consumption,and small volume.However,the acquisiti...Nanodevices based on the single nanoparticle represent innovative and promising technology,which could satisfy the increasing requirements of high accuracy,low energy consumption,and small volume.However,the acquisition of single particles involves complex operation,and the corresponding nanodevices display low-throughput.Herein,we present a facile strategy to construct a single-particle platform with high throughput via substrate surface potential modulated a large-area and large-spacing nanoparticle assembly.Such platform not only avoids optic interference but also ensures the independent electrically conductive channel of single particle on substrate.Therefore,the dark-field microscopic imaging and single-particle scattering signals collecting of individual nanoparticles with plasmonic effect are satisfactory achieved based on the platform,and the first success in the fabrication of nano-organic-light-emitting-diodes with single nanoparticle resolution in nanoscale.All the results indicate that the strategy may find promising applications in the in situ single-particle research such as single-particle detection,singleparticle catalysis,and optoelectronics.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Ministry of Science and ICT(No.2022M3J1A1085371)by the DGIST R&D programs of the Ministry of Science and ICT(23-ET-08 and 23-CoE-ET-01)supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2018R1A6A1A03025340).
文摘Cu2ZnSn(S,Se)4(CZTSSe)solar cells have resource distribution and economic advantages.The main cause of their low efficiency is carrier loss resulting from recombination of photo-generated electron and hole.To overcome this,it is important to understand their electron-hole behavior characteristics.To determine the carrier separation characteristics,we measured the surface potential and the local current in terms of the absorber depth.The elemental variation in the intragrains(IGs)and at the grain boundaries(GBs)caused a band edge shift and bandgap(Eg)change.At the absorber surface and subsurface,an upward Ec and Ev band bending structure was observed at the GBs,and the carrier separation was improved.At the absorber center,both upward Ec and Ev and downward Ec-upward Ev band bending structures were observed at the GBs,and the carrier separation was degraded.To improve the carrier separation and suppress carrier recombination,an upward Ec and Ev band bending structure at the GBs is desirable.
文摘By calculating the energy distribution of electrons reaching the photocathode surface and solving the Schrodinger equation that describes the behavior of an electron tunneling through the surface potential barrier,we obtain an equation to calculate the emitted electron energy distribution of transmission-mode NEA GaAs photocathodes. Accord- ing to the equation,we study the effect of cathode surface potential barrier on the electron energy distribution and find a significant effect of the barrier-Ⅰ thickness or end height,especially the thickness,on the quantum efficiency of the cath- ode. Barrier Ⅱ has an effect on the electron energy spread, and an increase in the vacuum level will lead to a narrower electron energy spread while sacrificing a certain amount of cathode quantum efficiency. The equation is also used to fit the measured electron energy distribution curve of the transmission-mode cathode and the parameters of the surface barri- er are obtained from the fitting. The theoretical curve is in good agreement with the experimental curve.
文摘A continuous and analytical surface potential model for SOI LDMOS, which accounts for automatic transitions between fully and partially-depleted statuses,is presented. The surface potential equation of the SOI de- vice is solved by using the PSP′s accurate algorithm of surface potential,and the front and back surface potentials are obtained analytically as a function of gate and drain voltage. The formulations of inversion charge and body charge under the fully-depleted state have been modified. The continuous and analytical DC model for SOl LD- MOS is given based on PSP. The comparisons between simulation and measurements indicate that this model can predict the DC characteristics of SOI LDMOS accurately.
文摘A refinement of an analytical approximation of the surface potential in MOSFETs is proposed by introducing a high-order term. As compared to the conventional treatment with accuracy between 1nV and 0. 03mV in the cases with an oxide thickness tox = 1 ～ 10nm and substrate doping concentration Na = 1015 ～ 1018 cm-3 , this method yields an accuracy within about 1pV in all cases. This is comparable to numerical simulations, but does not require trading off much computation efficiency. More importantly, the spikes in the error curve associated with the traditional treatment are eliminated.
基金the Key-Area Research and Development Program of Guangdong Province(No.2018B010109009)the Shenzhen Science and Technology Innovation Committee(Nos.JCYJ20170818155752559 and JCYJ20170818160815002)+3 种基金the Instrument Developing Project of Chinese Academy of Sciences(No.ZDKYYQ20180004)the National Natural Science Foundation of China(No.11872203)the National Natural Science Foundation of China for Creative Research Groups(No.51921003)support of the China Scholarship Council。
文摘As a fundamental surface property of two-dimensional(2 D)materials,surface potential is critical for their emerging electronic applications and essential for van der Waals heterostructure engineering.Here,we report the surface potential of few-layer InSe.The effect of layer count,light intensity and different deposited substrates is considered.Few-layer InSe flakes were exfoliated from bulk InSe crystals on Si/SiO_(2)with 300-nm-thick thermal oxide and Si/SiO_(2)with 300-nm-thick thermal oxide and prefabricated micro-wells with 3μm in diameter.The samples were measured by Kelvin probe force microscopy and tuned by an integrated 405-nm(3.06 eV)laser.Based on the work function of SiO_(2)(5.00 eV),the work functions of supported and suspended InSe are determined.These results show that the work function of InSe decreases with the increase in the layer count of both supported InSe and suspended InSe.Besides,by introducing a tunable laser light,the influence of light intensity on surface potential of supported InSe was studied.The surface potential(SP)and surface potential shift between light and dark states(ASP=SP_(lignt)-SP_(dark))of supported InSe were measured and determined.These results present that the surface potential of supported InSe decreases with the increase in the light intensity and also decreases with the increase in the layer count.This is evident that light excites electrons,resulting in decreased surface potential,and the amount of electrons excited is correlated with light intensity.Meanwhile,⊿SP between light and dark states decreases with the increase in the layer count,which suggests that the influence of light illumination decreases with the increase in the layer count of few-layer InSe flakes.
基金the National Natural Science Foundation of China(Grant Nos.91837101,42122035,and 91937302)the National Key Research and Development Program of China(Grant No.2018YFC1505706 and 2020YFA0608903).
文摘The influences of interannual surface potential vorticity forcing over the Tibetan Plateau(TP)on East Asian summer rainfall(EASR)and upper-level circulation are explored in this study.The results show that the interannual EASR and associated circulations are closely related to the surface potential vorticity negative uniform leading mode(PVNUM)over the TP.When the PVNUM is in the positive phase,more rainfall occurs in the Yangtze River valley,South Korea,Japan,and part of northern China,less rainfall occurs in southern China,and vice versa.A possible mechanism by which PVNUM affects EASR is proposed.Unstable air induced by the positive phase of PVNUM could stimulate significant upward motion and a lower-level anomalous cyclone over the TP.As a result,a dipole heating mode with anomalous cooling over the southwestern TP and anomalous heating over the southeastern TP is generated.Sensitivity experiment results regarding this dipole heating mode indicate that anomalous cooling over the southwestern TP leads to local and northeastern Asian negative height anomalies,while anomalous heating over the southeastern TP leads to local positive height anomalies.These results greatly resemble the realistic circulation pattern associated with EASR.Further analysis indicates that the anomalous water vapor transport associated with this anomalous circulation pattern is responsible for the anomalous EASR.Consequently,changes in surface potential vorticity forcing over the TP can induce changes in EASR.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41501240,41530855,41501241,and 41877026)the Natural Science Foundation of Chongqing CSTC(Grant No.cstc2018jcyjAX0318)the Fundamental Research Funds for the Central Universities,China(Grant No.XDJK2017B029)
文摘Surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson–Boltzmann theory with the consideration of the dielectric decrement in mixed electrolyte. The analytical relationships between surface potential and charge density are derived in different mixed electrolytes with monovalent and bivalent ions. The dielectric decrease on the charged surface strongly affects the surface potential at a high charge density with different ion strengths and concentration ratios of counter-ions. The surface potential based on the Gouy–Chapman model is underestimated because of the dielectric decrement on the surface. The diffuse layer can be regarded as a continuous uniform medium only when the surface charge density is lower than 0.3 C·m-2. However, the surface charge densities of many materials in practical applications are higher than 0.3 C·m-2. The new model for the estimation of surface potential can return to the results obtained based on the Gouy–Chapman model at a low charge density. Therefore, it is implied that the established model that considers the dielectric decrement is valid and widely applicable.
基金Project supported in part by the National Natural Science Foundation of China (Grant No. 62104192)in part by the Natural Science Basic Research Program of Shaanxi Province (Grant No. 2021JQ-717)。
文摘Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor(H-TFET). This model accounts for both the effects of source depletion and inversion charge, which are the key factors influencing the charge, capacitance and current in H-TFET. The accuracy of the model is validated against TCAD simulation and is greatly improved in comparison with the conventional model based on Maxwell–Boltzmann approximation. Furthermore, the dependences of the surface potential and electric field on biases are well predicted and thoroughly analyzed.
基金Project supported by the National Natural Science Foundation of China （Grant No 603776024）.
文摘The improvement of the characteristics of grooved-gate MOSFETs compared to the planar devices is attributed to the corner effect of the surface potential along the channel. In this paper we propose an analytical model of the surface potential distribution based on the solution of two-dimensional Poisson equation in cylindrical coordinates utilizing the cylinder approximation and the structure parameters such as the concave corner θ0. The relationship between the minimum surface potential and the structure parameters is theoretically analysed. Results confirm that the bigger the concave corner, the more obvious the corner effect. The corner effect increases the threshold voltage of the grooved-gate MOSFETs, so the better is the short channel effect （SCE） immunity.
文摘Simultaneous measurements of surface pressure and surface potential and scanning tunneling microscopy study for N-docosylpyridinium- TCNQ monolayer were carried out.These methods allow us to get more informations on properties of the monolayer.The molecules at the final stage of compression are really in compact stack although a voluminous hydrophilic head exists in the molecule.
文摘In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.
文摘The immobilization of biomaterials on a carrier is the first step for many different applications in life science and medicine. The usage of surface-near electrostatic forces is one possible approach to guide the charged biomaterials to a specific location on the carrier. In this study, we investigate the effect of intrinsic defects on the surface potential of silicon carriers in the dark and under illumination by means of Kelvin probe force microscopy. The intrinsic defects were introduced into the carrier by local, stripe-patterned ion implantation of silicon ions with a fluence of 3 × 10<sup>13</sup> Si ions/cm<sup>2</sup> and 3 × 10<sup>15</sup> Si ions/cm<sup>2</sup> into a p-type silicon wafer with a dopant concentration of 9 × 10<sup>15</sup> B/cm<sup>3</sup>. The patterned implantation allows a direct comparison between the surface potential of the silicon host against the surface potential of implanted stripes. The depth of the implanted silicon ions in the target and the concentration of displaced silicon atoms was simulated using the Stopping and Range of Ions in Matter (SRIM) software. The low fluence implantation shows a negligible effect on the measured Kelvin bias in the dark, whereas the large fluence implantation leads to an increased Kelvin bias, i.e. to a smaller surface work function according to the contact potential difference model. Illumination causes a reduced surface band bending and surface potential in the non-implanted regions. The change of the Kelvin bias in the implanted regions under illumination provides insight into the mobility and lifetime of photo-generated electron-hole pairs. Finally, the effect of annealing on the intrinsic defect density is discussed and compared with atomic force microscopy measurements on the 2<sup>nd</sup> harmonic. In addition, by using the Baumgart, Helm, Schmidt interpretation of the measured Kelvin bias, the dopant concentration after implantation is estimated.
基金supported by the National Natural Science Foundation of China(51607041)China State Key Lab of Power Systems(SKLD19KM06)。
文摘The effect of barrier material on AC breakdown voltages of a hybrid gas-solid insulation is investigated by examining the behavior of electrostatic potential on barrier surfaces.Breakdown characteristics of air-insulated gaps with barriers made of three different polymeric materials are experimentally investigated.Further,measurements of surface potential on the barriers are performed and the results are utilized to obtain surface charge dynamic characteristics for the three polymeric materials and extract their electric conductivities,charge carrier mobilities,and trap energy distributions.It is found that the material with the lowest initial surface potential and fastest decay rate exhibits the highest bulk conductivity and carriers'mobility,as well as the lowest trap energy level.These properties provide the highest increase in AC breakdown voltages compared with pure air.It is concluded that materials where the accumulation of charges in the bulk is inhibited and decay of surface charges is facilitated,allow for higher operating voltages of AC hybrid gas-solid insulation systems.The mechanism of the effect of barrier material on AC breakdown voltage is discussed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.52002318 and 22103061)。
文摘Potential energy surfaces(PESs), vibrational frequencies, and infrared spectra are calculated for NF_(3)^(+) using ab initio calculations, based on UCCSD(T)/cc-p VTZ combined with vibrational configuration interaction(VCI). Based on an iterative algorithm, the surfaces(SURF) program adds automatic points to the lattice representation of the potential function, the one-dimensional and two-dimensional PESs are calculated after reaching a convergence threshold, finally the smooth image of the potential energy surface is fitted. The PESs accurately account for the interaction between the different modes, with the mode q_(6) symmetrical stretching vibrations having the greatest effect on the potential energy change of the whole system throughout the potential energy surface shift. The anharmonic frequencies are obtained when the VCI matrix is diagonalized. Fundamental frequencies, overtones, and combination bands of NF_(3)^(+) are calculated, which generate the degenerate phenomenon between their frequencies. Finally, the calculated anharmonic frequency is used to plot the infrared spectra.Modal antisymmetric stretching ν_(5) and symmetric stretching ν_(6) exhibit a phenomenon of large-intensity borrowing. This study can provide data to support the characterization in the laboratory.
基金Project supported by the National Natural Science Foundation of China(No.60876027)the Competitive Earmarked Program from the Research Grant Council of Hong Kong SAR,China(No.HKUST6289/04E)+1 种基金the Industry,Education and Academy Cooperation Program of Guangdong Province,China(No.2009B090300318)the Fundamental Research Project of Shenzhen Science & Technology Foundation,China(No.JC200903160353A).
文摘A continuous surface potential versus voltage equation is proposed and then its solution is further discussed for a long channel intrinsic surrounding-gate（SRG） MOSFET from the accumulation to strong inversion region.The original equation is derived from the exact solution of a simplified Poisson equation and then the empirical correction is performed from the mathematical condition required by the continuity of the solution,which results in a continuous surface potential versus voltage equation,allowing the surface potential and the related derivatives to be described by an analytic solution from the accumulation to strong inversion region and from linear to the saturation region accurately and continuously.From these results,the dependences of surface potential and centric potential characteristics on device geometry are analyzed and the results are also verified with the 3-D numerical simulation from the aspect of accuracy and continuity tests.
基金supported by the European Horizon 2020 grant“SensApp”under Grant Agreement No.829104.
文摘The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices.Pyroelectric current measurement is the commonly employed method,but can be complex and requires surface electrodes.Here,we present noncontact electrostatic voltmeter measurements as a simple but highly accurate alternative,by assessing thermally-induced pyroelectric surface potential variations.We introduce a refined model that relates the surface potential variations to both the pyroelectric coefficient and the characteristic figure of merit(FOM)and test the model with square-shaped samples made from PVDF,LiNbO3 and LiTaO3.The characteristic pyroelectric coefficient for PVDF,LiNbO3 and LiTaO3 was found to be 33.4,59.9 and 208.4μC m−2 K−1,respectively.These values are in perfect agreement with literature values,and they differ by less than 2.5%from values that we have obtained with standard pyroelectric current measurements for comparison.
基金This work was supported by the National Natural Science Foundation of China （No.21103003）.
文摘The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311＋ G（2d,2p） method. The potential energy surfaces （PES） along the O-N and O-O bonds have been scanned at CCSD（T）/aug-cc-pVDZ level, respectively. The calculated results show that on the O-N PES, the O3-N4 bond length of the loose transition state is 2.82A^° and the corresponding energy barrier is 25.6 kcal/mol, while on the O-O PES, the loose transition state with of O2-O3 bond length of 2.35A^° has the energy barrier of 37.4 kcal/mol. Thus the primary reaction path for peroxynitric acid is the dissociation into HO2 and NO2.
基金Supported by the Fundamental Research Funds for the Central Universities in Nanjing University of Aeronautics and Astronautics under Grant No NS2014089
文摘Surface potential decay of polymers for electrical insulation can help to determine the dark conductivity for spacecraft charging analysis. Due to the existence of radiation-induced conductivity, it decays fast in the first few hours after irradiation and exponentially slowly for the remaining time. The measurement of dark conductivity with this method usually takes the slow part and needs a couple of days. Integrating the Fowler formula into the deep dielectric charging equations, we obtain a new expression for the fast decay part. The experimental data of different materials, dose rates and temperatures are fitted by the new expression. Both the dark conductivity and the radiation-induced conductivity are derived and compared with other methods. The result shows a good estimation of dark conductivity and radiation-induced conductivity in high-resistivity polymers, which enables a fast measurement of dielectric conductivity within about 600 rain after irradiation.
文摘Based on current voltage（I-Vg） and capacitance voltage（C-Vg） measurements,a reliable procedure is proposed to determine the effective surface potential Vd（Vg） in Schottky diodes.In the framework of thermionic emission,our analysis includes both the effect of the series resistance and the ideality factor,even voltage dependent. This technique is applied to n-type indium phosphide（n-InP） Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-Vg measurements.The study clearly shows that the depletion width and the flat band barrier height deduced from C-Vg,which are important parameters directly related to the surface potential in the semiconductor,should be estimated within our approach to obtain more reliable information.
基金supported by the National Natural Science Foundation of China(Nos.21822202 and 22072104)the National Key R&D Program of China(International Collaboration program)granted by the Chinese Ministry of Science and Technology(No.2018YFE0200700).
文摘Nanodevices based on the single nanoparticle represent innovative and promising technology,which could satisfy the increasing requirements of high accuracy,low energy consumption,and small volume.However,the acquisition of single particles involves complex operation,and the corresponding nanodevices display low-throughput.Herein,we present a facile strategy to construct a single-particle platform with high throughput via substrate surface potential modulated a large-area and large-spacing nanoparticle assembly.Such platform not only avoids optic interference but also ensures the independent electrically conductive channel of single particle on substrate.Therefore,the dark-field microscopic imaging and single-particle scattering signals collecting of individual nanoparticles with plasmonic effect are satisfactory achieved based on the platform,and the first success in the fabrication of nano-organic-light-emitting-diodes with single nanoparticle resolution in nanoscale.All the results indicate that the strategy may find promising applications in the in situ single-particle research such as single-particle detection,singleparticle catalysis,and optoelectronics.
