We investigated the surface potential dynamics of a ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIMNT) single crystal using Kelvin probe force microscopy (KPFM). The initial surface potential is a function...We investigated the surface potential dynamics of a ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIMNT) single crystal using Kelvin probe force microscopy (KPFM). The initial surface potential is a function of the applied bias since it reflects the interplay between the polarisation and screen charges. It is suggested that the different rates of tip injected charges are responsible for the asymmetric behaviour of the initial surface potential dependent on the sign of the applied bias. The polarisation, screen and tip injected charges are considered to explain the difference in surface potential dynamics.展开更多
The tribological properties and scratch resistance of MoS_(2)bilayer deposited on SiO_(2)/Si substrates prepared via chemical vapor deposition are investigated.Friction force microscopy(FFM)is employed to investigate ...The tribological properties and scratch resistance of MoS_(2)bilayer deposited on SiO_(2)/Si substrates prepared via chemical vapor deposition are investigated.Friction force microscopy(FFM)is employed to investigate the friction and wear properties of the MoS_(2)bilayer at the nanoscale by applying a normal load ranging from 200 to 1,000 nN.Scratch resistance is measured using the scratch mode in FFM based on a linearly increasing load from 100 to 1,000 nN.Kelvin probe force microscopy(KPFM)is performed to locally measure the surface potential in the tested surface to qualitatively measure the wear/removal of Mos,layers and identify critical loads associated with the individual failures of the top and bottom layers.The analysis of the contact potential difference values as well as that of KPFM,friction,and height images show that the wear/removal of the top and bottom layers in the MoS_(2)bilayer system occurred consecutively.The FFM and KPFM results show that the top MoS_(2)layer begins to degrade at the end of the low friction stage,followed by the bottom layer,thereby resulting in a transitional friction stage owing to the direct contact between the diamond tip and SiO_(2)substrate.In the stable third stage,the transfer of lubricious MoS_(2)debris to the tip apex results in contact between the MoS_(2)-transferred tip and SiO_(2).Nanoscratch test results show two ranges of critical loads,which correspond to the sequential removal of the top and bottom layers.展开更多
We report on an electrostatically formed nanowire （EFN）-based sensor with tunable diameters in the range of 16 nm to 46 nm and demonstrate an EFN- based field-effect transistor as a highly sensitive and robust room ...We report on an electrostatically formed nanowire （EFN）-based sensor with tunable diameters in the range of 16 nm to 46 nm and demonstrate an EFN- based field-effect transistor as a highly sensitive and robust room temperature gas sensor. The device was carefully designed and fabricated using standard integrated processing to achieve the 16 nm EFN that can be used for sensing without any need for surface modification. The effective diameter for the EFN was determined using Kelvin probe force microscopy accompanied by three- dimensional electrostatic simulations. We show that the EFN transistor is capable of detecting 100 parts per million of ethanol gas with bare SiO2.展开更多
The kesterite-structured semiconductor Cu_2 Zn Sn(S,Se)_4(CZTSSe) is prepared by spin coating a non-hydrazine precursor and annealing at Se atmosphere. Local electrical and optoelectronic properties of the CZTSSe thin...The kesterite-structured semiconductor Cu_2 Zn Sn(S,Se)_4(CZTSSe) is prepared by spin coating a non-hydrazine precursor and annealing at Se atmosphere. Local electrical and optoelectronic properties of the CZTSSe thin-film are explored by Kelvin probe force microscopy and conductive atomic force microscopy. Before and after irradiation, no marked potential bending and very low current flow are observed at GBs, suggesting that GBs behave as a charge recombination site and an obstacle for charge transport. Furthermore, Cd S nano-islands are synthesized via successive ionic layer adsorption and reaction(SILAR) method on the surface of CZTSSe. By comparing the work function and current flow change of CZTSSe and Cd S in dark and under illumination, we demonstrate photo-induced electrons and holes are separated at the interface of p-n junction and transferred in Cd S and CZTSSe, respectively.展开更多
Control of blend morphology at multi-scale is critical for optimizing the power conversion efficiency(PCE)of plastic solar cells.To better understand the physics of photoactive layer in the organic photovoltaic device...Control of blend morphology at multi-scale is critical for optimizing the power conversion efficiency(PCE)of plastic solar cells.To better understand the physics of photoactive layer in the organic photovoltaic devices,it is necessary to gain understanding of morphology and the corresponding electronic property.Herein we report the correlation between nanoscale structural,electric properties of bulk heterojunction(BHJ)solar cells and the annealing-induced PCE change.We demonstrate that the PCE of BHJ solar cells are dramatically improved(from1.3%to 4.6%)by thermal annealing,which results from P3HT crystalline stacking and the PCBM aggregation for interpenetrated network.The similar trend for annealinginduced photovoltage and PCE evolution present as an initial increase followed by a decrease with the annealing time and temperature.The surface roughness increase slowly and then abruptly after the same inflection points observed for photovoltage and PCE.The phase images in electric force microscopy indicate the optimized P3HT and PCBM crystallization for interpenetrating network formation considering the spectroscopic results as well.From the correlation between surface photovoltage,blend morphology,and PCE,we propose a model to illustrate the film structure and its evolution under different annealing conditions.This work would benefit the better design and optimization of the morphology and local electric properties of solar cell active layers for improved PCE.展开更多
文摘We investigated the surface potential dynamics of a ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIMNT) single crystal using Kelvin probe force microscopy (KPFM). The initial surface potential is a function of the applied bias since it reflects the interplay between the polarisation and screen charges. It is suggested that the different rates of tip injected charges are responsible for the asymmetric behaviour of the initial surface potential dependent on the sign of the applied bias. The polarisation, screen and tip injected charges are considered to explain the difference in surface potential dynamics.
基金This study was supported by the Research Program funded by the SeoulTech(Seoul National University of Science and Technology,Republic of Korea).
文摘The tribological properties and scratch resistance of MoS_(2)bilayer deposited on SiO_(2)/Si substrates prepared via chemical vapor deposition are investigated.Friction force microscopy(FFM)is employed to investigate the friction and wear properties of the MoS_(2)bilayer at the nanoscale by applying a normal load ranging from 200 to 1,000 nN.Scratch resistance is measured using the scratch mode in FFM based on a linearly increasing load from 100 to 1,000 nN.Kelvin probe force microscopy(KPFM)is performed to locally measure the surface potential in the tested surface to qualitatively measure the wear/removal of Mos,layers and identify critical loads associated with the individual failures of the top and bottom layers.The analysis of the contact potential difference values as well as that of KPFM,friction,and height images show that the wear/removal of the top and bottom layers in the MoS_(2)bilayer system occurred consecutively.The FFM and KPFM results show that the top MoS_(2)layer begins to degrade at the end of the low friction stage,followed by the bottom layer,thereby resulting in a transitional friction stage owing to the direct contact between the diamond tip and SiO_(2)substrate.In the stable third stage,the transfer of lubricious MoS_(2)debris to the tip apex results in contact between the MoS_(2)-transferred tip and SiO_(2).Nanoscratch test results show two ranges of critical loads,which correspond to the sequential removal of the top and bottom layers.
文摘We report on an electrostatically formed nanowire （EFN）-based sensor with tunable diameters in the range of 16 nm to 46 nm and demonstrate an EFN- based field-effect transistor as a highly sensitive and robust room temperature gas sensor. The device was carefully designed and fabricated using standard integrated processing to achieve the 16 nm EFN that can be used for sensing without any need for surface modification. The effective diameter for the EFN was determined using Kelvin probe force microscopy accompanied by three- dimensional electrostatic simulations. We show that the EFN transistor is capable of detecting 100 parts per million of ethanol gas with bare SiO2.
基金supported by the National Basic Research Program of China(2011CB9323012011CB808704)+2 种基金the National Natural Science Foundation of China(2112790121373236)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB12020100)
文摘The kesterite-structured semiconductor Cu_2 Zn Sn(S,Se)_4(CZTSSe) is prepared by spin coating a non-hydrazine precursor and annealing at Se atmosphere. Local electrical and optoelectronic properties of the CZTSSe thin-film are explored by Kelvin probe force microscopy and conductive atomic force microscopy. Before and after irradiation, no marked potential bending and very low current flow are observed at GBs, suggesting that GBs behave as a charge recombination site and an obstacle for charge transport. Furthermore, Cd S nano-islands are synthesized via successive ionic layer adsorption and reaction(SILAR) method on the surface of CZTSSe. By comparing the work function and current flow change of CZTSSe and Cd S in dark and under illumination, we demonstrate photo-induced electrons and holes are separated at the interface of p-n junction and transferred in Cd S and CZTSSe, respectively.
基金supported by the National Basic Research Program of China(2011CB932800 and 2013CB934200)Sino-British Collaboration Program(2010DFA64680)+1 种基金National Natural Science Foundation of China(20973043)Chinese Academy of Sciences(KGCX2-YW-375-3)
文摘Control of blend morphology at multi-scale is critical for optimizing the power conversion efficiency(PCE)of plastic solar cells.To better understand the physics of photoactive layer in the organic photovoltaic devices,it is necessary to gain understanding of morphology and the corresponding electronic property.Herein we report the correlation between nanoscale structural,electric properties of bulk heterojunction(BHJ)solar cells and the annealing-induced PCE change.We demonstrate that the PCE of BHJ solar cells are dramatically improved(from1.3%to 4.6%)by thermal annealing,which results from P3HT crystalline stacking and the PCBM aggregation for interpenetrated network.The similar trend for annealinginduced photovoltage and PCE evolution present as an initial increase followed by a decrease with the annealing time and temperature.The surface roughness increase slowly and then abruptly after the same inflection points observed for photovoltage and PCE.The phase images in electric force microscopy indicate the optimized P3HT and PCBM crystallization for interpenetrating network formation considering the spectroscopic results as well.From the correlation between surface photovoltage,blend morphology,and PCE,we propose a model to illustrate the film structure and its evolution under different annealing conditions.This work would benefit the better design and optimization of the morphology and local electric properties of solar cell active layers for improved PCE.
