In-hand manipulation is a fundamental ability for multi-fingered robotic hands that interact with their environments.Owing to the high dimensionality of robotic hands and intermittent contact dynamics,effectively prog...In-hand manipulation is a fundamental ability for multi-fingered robotic hands that interact with their environments.Owing to the high dimensionality of robotic hands and intermittent contact dynamics,effectively programming a robotic hand for in-hand manipulations is still a challenging problem.To address this challenge,this work employs deep reinforcement learning(DRL)algorithm to learn in-hand manipulations for multi-fingered robotic hands.A reward-shaping method is proposed to assist the learning of in-hand manipulation.The synergy of robotic hand postures is analysed to build a low-dimensional hand posture space.Two additional rewards are designed based on both the analysis of hand synergies and its learning history.The two additional rewards cooperating with an extrinsic reward are used to assist the in-hand manipulation learning.Three value functions are trained jointly with respect to their reward functions.Then they cooperate to optimise a control policy for in-hand manipulation.The reward shaping not only improves the exploration efficiency of the DRL algorithm but also provides a way to incorporate domain knowledge.The performance of the proposed learning method is evaluated with object rotation tasks.Experimental results demonstrated that the proposed learning method enables multi-fingered robotic hands to learn in-hand manipulation effectively.展开更多
We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to ba...We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to basically have the same good electric characteristics as the chips on Si substrates.Furthermore,the better heat dissipation of HEMTs on Cu substrates compared to HEMTs on Si substrates is clearly observed by thermoreflectance imaging,showing the promising potential for very high-power and high-temperature operation.This work shows the outstanding ability of HEMT chips on Cu substrates for solving the self-heating effect with the advantages of process simplicity,high yield,and low production requirement.展开更多
In traditional nasal surgery,surgeons are prone to fatigue and jitter by holding the endoscope for a long‐time.Some complex operations require assistant surgeon to assist with holding the endoscope.To address the abo...In traditional nasal surgery,surgeons are prone to fatigue and jitter by holding the endoscope for a long‐time.Some complex operations require assistant surgeon to assist with holding the endoscope.To address the above problems,the authors design a remote centre of motion based nasal robot,and propose a voice‐based robot control method.First,through the operation space analysis of nasal surgery,the design scheme of the robot based on RCM mechanism is proposed.On this basis,the design parameters of the robot are analysed to complete the entire design of robot.Then,considering that the surgeon's hands are occupied by surgical instruments during complex surgical operations,a voice‐based robot control method is proposed.This method obtains direction instructions from surgeons by analysing the movement of the endoscopic image.Afterward,a commercial speech recognition interface is used to realise the offline grammar controlwords lib compatible with both Chinese and English,and the overall strategy of robot control is proposed.Finally,an experimental platform for virtual robot control is established,and the voice‐based robot control experiment is performed.The results show that the proposed voice‐based control method is feasible,and it provides guidance for the subsequent development and control of the actual robot system.展开更多
1.Objective As an important component of the southern Central Asian Orogenic Belt(CAOB),North Xinjiang in NW China is characterized by numerous Cu-Ni sulfide-bearing maficultramafic intrusions,and this region constitu...1.Objective As an important component of the southern Central Asian Orogenic Belt(CAOB),North Xinjiang in NW China is characterized by numerous Cu-Ni sulfide-bearing maficultramafic intrusions,and this region constitutes the secondlargest Cu-Ni metallogenic province in China.Zircon U-Pb chronology studies reveal that these intrusions predominantly formed in the Early Permian(300–270 Ma;Qin KZ et al.,2011).展开更多
Absorption coefficient is a physical parameter to describe electromagnetic energy absorption of materials, which is closely related to solar cells and photodetectors. We grow a series of positive-intrinsic-negative(PI...Absorption coefficient is a physical parameter to describe electromagnetic energy absorption of materials, which is closely related to solar cells and photodetectors. We grow a series of positive-intrinsic-negative(PIN) structures on silicon wafer by a gas source molecule beam epitaxy system and the investigate the absorption coefficient through the photovoltaic processes in detail. It is found that the absorption coefficient is enhanced by one order and can be tuned greatly through the thickness of the intrinsic layer in the PIN structure, which is also demonstrated by the 730-nm-wavelength laser irradiation. These results cannot be explained by the traditional absorption theory.We speculate that there could be some uncovered mechanism in this system, which will inspire us to understand the absorption process further.展开更多
The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of th...The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, Ga As based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells,photodetectors, and other photoelectric devices.展开更多
Quantum confinement is recognized to be an inherent property in low-dimensional structures.Traditionally,it is believed that the carriers trapped within the well cannot escape due to the discrete energy levels.However...Quantum confinement is recognized to be an inherent property in low-dimensional structures.Traditionally,it is believed that the carriers trapped within the well cannot escape due to the discrete energy levels.However,our previous research has revealed efficient carrier escape in low-dimensional structures,contradicting this conventional understanding.In this study,we review the energy band structure of quantum wells along the growth direction considering it as a superposition of the bulk material dispersion and quantization energy dispersion resulting from the quantum confinement across the whole Brillouin zone.By accounting for all wave vectors,we obtain a certain distribution of carrier energy at each quantized energy level,giving rise to the energy subbands.These results enable carriers to escape from the well under the influence of an electric field.Additionally,we have compiled a comprehensive summary of various energy band scenarios in quantum well structures relevant to carrier transport.Such a new interpretation holds significant value in deepening our comprehension of low-dimensional energy bands,discovering new physical phenomena,and designing novel devices with superior performance.展开更多
Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semiconductor structures and exploring their potential applications in practice. For quantum well structures...Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semiconductor structures and exploring their potential applications in practice. For quantum well structures, the energy of carriers in the well splits into discrete energy levels due to the confinement of barriers in the growth direction. However, the discrete energy levels obtained at a fixed wave vector cannot accurately reflect the actual energy band structure. In this work, the band structure of the type-II quantum wells is reanalyzed. When the wave vectors of the entire Brillouin region(corresponding to the growth direction) are taken into account, the quantized energy levels of the carriers in the well are replaced by subbands with certain energy distributions. This new understanding of the energy bands of low-dimensional structures not only helps us to have a deeper cognition of the structure, but also may overturn many viewpoints in traditional band theories and serve as supplementary to the band theory of low-dimensional systems.展开更多
N-polar GaN film was obtained by using a high-temperature AlN buffer layer.It was found that the polarity could be inverted by a thin low-temperature AlN interlayer with the same V/III ratio as that of the high-temper...N-polar GaN film was obtained by using a high-temperature AlN buffer layer.It was found that the polarity could be inverted by a thin low-temperature AlN interlayer with the same V/III ratio as that of the high-temperature AlN layer.Continuing to increase the V/III ratio of the low-temperature AlN interlayer,the Ga-polarity of GaN film was inverted to N-polarity again but the crystal quality and surface roughness of GaN film greatly deteriorated.Finally,we analyzed the chemical environment of the AlN layer by x-ray photoelectron spectroscopy(XPS),which provides a new direction for the control of GaN polarity.展开更多
The absorption coefficient is usually considered as a constant for certain materials at the given wavelength.However,recent experiments demonstrated that the absorption coefficient could be enhanced a lot by the PN ju...The absorption coefficient is usually considered as a constant for certain materials at the given wavelength.However,recent experiments demonstrated that the absorption coefficient could be enhanced a lot by the PN junction.The absorption coefficient varies with the thickness of the intrinsic layer in a PIN structure.Here,we interpret the anomalous absorption coefficient from the competition between recombination and drift for non-equilibrium carriers.Based on the Fokker-Planck theory,a non-equilibrium statistical model that describes the relationship between absorption coefficient and material thickness has been proposed.It could predict the experimental data well.Our results can give new ideas to design photoelectric devices.展开更多
SiGe spheres with different diameters are successfully fabricated on a virtual SiGe template using a laser irradiation method.The results from scanning electron microscopy and micro-Raman spectroscopy reveal that the ...SiGe spheres with different diameters are successfully fabricated on a virtual SiGe template using a laser irradiation method.The results from scanning electron microscopy and micro-Raman spectroscopy reveal that the diameter and Ge composition of the SiGe spheres can be well controlled by adjusting the laser energy density.In addition,the transmission electron microscopy results show that Ge composition inside the SiGe spheres is almost uniform in a well-defined,nearly spherical outline.As a convenient method to prepare sphere-shaped SiGe micro/nanostructures with tunable Ge composition and size,this technique is expected to be useful for SiGe-based material growth and micro/optoelectronic device fabrication.展开更多
The contact characteristic between p-InP and metal plays an important role in InP-related optoelectronic and microelectronic device applications.We investigate the low-resistance Au/Pt/Ni and Au/Ni ohmic contacts to p...The contact characteristic between p-InP and metal plays an important role in InP-related optoelectronic and microelectronic device applications.We investigate the low-resistance Au/Pt/Ni and Au/Ni ohmic contacts to p-InP based on the solid phase regrowth principle.The lowest specific contact resistivity of Au(100 nm)/Pt(115 nm)/Ni(50 nm)can reach 2.64×10^(-6)Ω·cm^(2) after annealing at 380℃ for 1 min,while the contact characteristics of Au/Ni deteriorated after annealing from 340℃ to 480℃ for 1 min.The results of scanning electron microscopy,atomic force microscopy and x-ray photoelectron spectroscopy show that the Pt layer is an important factor in improving the contact characteristics.The Pt layer prevents the diffusion of In and Au,inhibits the formation of Au3In metal compounds,and prevents the deterioration of the ohmic contact.The metal structures and optimized annealing process is expected to be helpful for obtaining high-performance InP-related devices.展开更多
We demonstrate that a low-temperature Ga N insertion layer could significantly improve the surface morphology of non-polar a-plane Ga N.The two key factors in improving the surface morphology of non-polar a-plane Ga N...We demonstrate that a low-temperature Ga N insertion layer could significantly improve the surface morphology of non-polar a-plane Ga N.The two key factors in improving the surface morphology of non-polar a-plane Ga N are growth temperature and growth time of the Ga N insertion layer.The root-mean-square roughness of a-plane Ga N is reduced by 75%compared to the sample without the Ga N insertion layer.Meanwhile,the Ga N insertion layer is also beneficial for improving crystal quality.This work provides a simple and effective method to improve the surface morphology of non-polar a-plane Ga N.展开更多
It is known that the p–n junction of an absorption region is a crucial part for power conversion efficiency of photovoltaic power converters.We fabricate four samples with different dopant concentrations in base laye...It is known that the p–n junction of an absorption region is a crucial part for power conversion efficiency of photovoltaic power converters.We fabricate four samples with different dopant concentrations in base layers.The dependences of power conversion efficiency and fill factor on input power are displayed by photocurrent–voltage measurement.Photoluminescence characteristics under open circuit and connected circuit conditions are also studied.It is found that the status of p–n junction matching is the critical factor in affecting the power conversion efficiency.In addition,series resistance of photovoltaic power converters impairs the efficiency especially at high input powers.Both the key factors need to be considered to obtain high efficiency,and this work provides promising guidance on designing photovoltaic power converters.展开更多
Novel and promising chloride ion batteries(CIBs)that can operate at room temperature have attracted great attentions,due to the sustainable chloride-containing resources and high theoretical energy density.To achieve ...Novel and promising chloride ion batteries(CIBs)that can operate at room temperature have attracted great attentions,due to the sustainable chloride-containing resources and high theoretical energy density.To achieve the superior electrochemical properties of CIBs,the structure design of electrode materials is essential.Herein,2D NiAl-layered double hydroxide(NiAl-LDH)nanoarrays derived from Al2O3 are in-situ grafted to graphene(G)by atomic layer deposition(ALD)and hydrothermal method.The achieved NiAl-LDH@G hybrids with 2D NiAl-LDH arrays grown perpendicularly on graphene surface,can efficiently prevent the stacking of LDHs and enlarge specific surface area to provide more active sites.The NiAl-LDH@G cathode exhibits a maximum discharge capacity of 223.3 mA h g^(-1)and an excellent reversible capacity of 107 mA h g^(-1)over 500 cycles at 100 mA g^(-1)with a high coulombic efficiency around 96%,whereas pure NiAl-LDH has a discharge capacity of only 48.8 mA h g^(-1)and a coulombic efficiency(CE)of about 78%.More importantly,the NiAl-LDH@G electrode has a stable voltage at 1.9 V and an outstanding discharge capacity of higher than 72 mA h g^(-1)after 120 days.Additionally,XRD,XPS,and EDS have been employed to unveil the electrochemical reaction and Cl-storage mechanism of the NiAlLDH@G cathode in CIBs.This work opens a facile and reasonable way for improving electrochemical performance at anion-type rechargeable batteries in terms of cathode material design and mechanism interpretation.展开更多
Ultra-compact spectrometers have attracted significant attention for their potential applications in portable systems for biomedical analysis,environmental monitoring,spectral analysis,and astronomical observation.In ...Ultra-compact spectrometers have attracted significant attention for their potential applications in portable systems for biomedical analysis,environmental monitoring,spectral analysis,and astronomical observation.In this work,we propose a miniaturized InGaAs-based extended short-wave infrared(eSWIR)spectrometer based on a single n-graded-p junction with voltage-tunable optical response characteristics in the range from 1600to 2100 nm.We combine this unique optical characteristic with a regression algorithm to realize the reconstruction of an unknown spectrum.The spectrometer achieves a high responsivity of 0.73 A/W at 1650 nm,and a low dark current density of 3.91×10^(-5)A/cm^2 at 200 K,corresponding to a calculated detectivity of1.69×10^(11)cm·Hz^(1/2)/W.Such spectrometers compatible with standard Ⅲ-Ⅴprocesses can offer a pathway to greatly promote the development of miniaturized spectrometers.展开更多
An internal photoemission-based silicon photodetector detects light below the silicon bandgap at room temperature and can exhibit spectrally broad behavior,making it potentially suited to meet the need for a near-infr...An internal photoemission-based silicon photodetector detects light below the silicon bandgap at room temperature and can exhibit spectrally broad behavior,making it potentially suited to meet the need for a near-infrared pure Si photodetector.In this work,the implementation of a thin Au insertion layer into an ITO/n-Si Schottky photodetector can profoundly affect the barrier height and significantly improve the device performance.By fabricating a nanoscale thin Au layer and an ITO electrode on a silicon substrate,we achieve a well-behaved ITO/Au/n-Si Schottky diode with a record dark current density of 3.7×10^(−7) A/cm^(2) at−1 V and a high rectification ratio of 1.5×10^(8) at±1 V.Furthermore,the responsivity has been obviously improved without sacrificing the dark current performance of the device by decreasing the Au thickness.Such a silicon-based photodetector with an enhanced performance could be a promising strategy for the realization of a monolithic integrated pure silicon photodetector in optical communication.展开更多
Electromagnetic pollution and heat dissipation problems are becoming increasingly worthy of attention due to the rapid development of electronic devices,which puts forward an urgent demand for microwave absorbers with...Electromagnetic pollution and heat dissipation problems are becoming increasingly worthy of attention due to the rapid development of electronic devices,which puts forward an urgent demand for microwave absorbers with excellent thermal management performance.Herein,high-performance Co/carbon nanofiber(Co/CNF)microwave absorbers with high thermal conductivity were fabricated by facile step-by-step method.The microwave absorption properties can be readily tuned by adjusting the content and size of Co nanoparticles through concentration gradient adsorption.Benefiting from the formation of dielectric and magnetic coupling network,Co/CNF composites possess intensive dipole polarization,interface polarization,and magnetic loss.The optimal Co/CNF composites exhibit outstanding microwave absorption performance with a minimum reflection loss(RL)of−53.0 dB at 11.44 GHz,and a maximum effective absorption bandwidth(EAB)of 5.5 GHz.In addition,the thermal conductivities of the Co/CNF-natural rubber(Co/CNF-NR)composites are significantly improved.This work may inspire the exploration of high-efficiency heat-conduction microwave absorbers based on CNF.展开更多
基金This work was funded by the German Science Foundation(DFG)and the National Science Foundation of China(NSFC)in project Crossmodal Learning under contract Sonderforschungsbereich Transregio 169.
文摘In-hand manipulation is a fundamental ability for multi-fingered robotic hands that interact with their environments.Owing to the high dimensionality of robotic hands and intermittent contact dynamics,effectively programming a robotic hand for in-hand manipulations is still a challenging problem.To address this challenge,this work employs deep reinforcement learning(DRL)algorithm to learn in-hand manipulations for multi-fingered robotic hands.A reward-shaping method is proposed to assist the learning of in-hand manipulation.The synergy of robotic hand postures is analysed to build a low-dimensional hand posture space.Two additional rewards are designed based on both the analysis of hand synergies and its learning history.The two additional rewards cooperating with an extrinsic reward are used to assist the in-hand manipulation learning.Three value functions are trained jointly with respect to their reward functions.Then they cooperate to optimise a control policy for in-hand manipulation.The reward shaping not only improves the exploration efficiency of the DRL algorithm but also provides a way to incorporate domain knowledge.The performance of the proposed learning method is evaluated with object rotation tasks.Experimental results demonstrated that the proposed learning method enables multi-fingered robotic hands to learn in-hand manipulation effectively.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61704008 and 11574362)。
文摘We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to basically have the same good electric characteristics as the chips on Si substrates.Furthermore,the better heat dissipation of HEMTs on Cu substrates compared to HEMTs on Si substrates is clearly observed by thermoreflectance imaging,showing the promising potential for very high-power and high-temperature operation.This work shows the outstanding ability of HEMT chips on Cu substrates for solving the self-heating effect with the advantages of process simplicity,high yield,and low production requirement.
文摘In traditional nasal surgery,surgeons are prone to fatigue and jitter by holding the endoscope for a long‐time.Some complex operations require assistant surgeon to assist with holding the endoscope.To address the above problems,the authors design a remote centre of motion based nasal robot,and propose a voice‐based robot control method.First,through the operation space analysis of nasal surgery,the design scheme of the robot based on RCM mechanism is proposed.On this basis,the design parameters of the robot are analysed to complete the entire design of robot.Then,considering that the surgeon's hands are occupied by surgical instruments during complex surgical operations,a voice‐based robot control method is proposed.This method obtains direction instructions from surgeons by analysing the movement of the endoscopic image.Afterward,a commercial speech recognition interface is used to realise the offline grammar controlwords lib compatible with both Chinese and English,and the overall strategy of robot control is proposed.Finally,an experimental platform for virtual robot control is established,and the voice‐based robot control experiment is performed.The results show that the proposed voice‐based control method is feasible,and it provides guidance for the subsequent development and control of the actual robot system.
基金the National Key Research and Development Program of China(2018YFC0604002)the geological survey projects of China Geological Survey(DD20190071,DD20160007).
文摘1.Objective As an important component of the southern Central Asian Orogenic Belt(CAOB),North Xinjiang in NW China is characterized by numerous Cu-Ni sulfide-bearing maficultramafic intrusions,and this region constitutes the secondlargest Cu-Ni metallogenic province in China.Zircon U-Pb chronology studies reveal that these intrusions predominantly formed in the Early Permian(300–270 Ma;Qin KZ et al.,2011).
基金Supported by the National Natural Science Foundation of China under Grant No 11574362
文摘Absorption coefficient is a physical parameter to describe electromagnetic energy absorption of materials, which is closely related to solar cells and photodetectors. We grow a series of positive-intrinsic-negative(PIN) structures on silicon wafer by a gas source molecule beam epitaxy system and the investigate the absorption coefficient through the photovoltaic processes in detail. It is found that the absorption coefficient is enhanced by one order and can be tuned greatly through the thickness of the intrinsic layer in the PIN structure, which is also demonstrated by the 730-nm-wavelength laser irradiation. These results cannot be explained by the traditional absorption theory.We speculate that there could be some uncovered mechanism in this system, which will inspire us to understand the absorption process further.
基金Project supported by the National Natural Science Foundation of China(Grant No.61991441)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000).
文摘The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, Ga As based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells,photodetectors, and other photoelectric devices.
基金the National Natural Science Foundation of China(Grant Nos.61991441 and 62004218)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB01000000)Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2021005).
文摘Quantum confinement is recognized to be an inherent property in low-dimensional structures.Traditionally,it is believed that the carriers trapped within the well cannot escape due to the discrete energy levels.However,our previous research has revealed efficient carrier escape in low-dimensional structures,contradicting this conventional understanding.In this study,we review the energy band structure of quantum wells along the growth direction considering it as a superposition of the bulk material dispersion and quantization energy dispersion resulting from the quantum confinement across the whole Brillouin zone.By accounting for all wave vectors,we obtain a certain distribution of carrier energy at each quantized energy level,giving rise to the energy subbands.These results enable carriers to escape from the well under the influence of an electric field.Additionally,we have compiled a comprehensive summary of various energy band scenarios in quantum well structures relevant to carrier transport.Such a new interpretation holds significant value in deepening our comprehension of low-dimensional energy bands,discovering new physical phenomena,and designing novel devices with superior performance.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61991441 and 62004218)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB01000000)Youth Innovation Promotion Association Chinese Academy of Sciences (Grant No. 2021005)。
文摘Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semiconductor structures and exploring their potential applications in practice. For quantum well structures, the energy of carriers in the well splits into discrete energy levels due to the confinement of barriers in the growth direction. However, the discrete energy levels obtained at a fixed wave vector cannot accurately reflect the actual energy band structure. In this work, the band structure of the type-II quantum wells is reanalyzed. When the wave vectors of the entire Brillouin region(corresponding to the growth direction) are taken into account, the quantized energy levels of the carriers in the well are replaced by subbands with certain energy distributions. This new understanding of the energy bands of low-dimensional structures not only helps us to have a deeper cognition of the structure, but also may overturn many viewpoints in traditional band theories and serve as supplementary to the band theory of low-dimensional systems.
基金Project supported by the National Natural Science Foundation of China(Grant No.62004218)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000).
文摘N-polar GaN film was obtained by using a high-temperature AlN buffer layer.It was found that the polarity could be inverted by a thin low-temperature AlN interlayer with the same V/III ratio as that of the high-temperature AlN layer.Continuing to increase the V/III ratio of the low-temperature AlN interlayer,the Ga-polarity of GaN film was inverted to N-polarity again but the crystal quality and surface roughness of GaN film greatly deteriorated.Finally,we analyzed the chemical environment of the AlN layer by x-ray photoelectron spectroscopy(XPS),which provides a new direction for the control of GaN polarity.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61804176,61991441,and 62004218)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB01000000)the Youth Innovation Promotion Association of Chinese Academy of Sciences.
文摘The absorption coefficient is usually considered as a constant for certain materials at the given wavelength.However,recent experiments demonstrated that the absorption coefficient could be enhanced a lot by the PN junction.The absorption coefficient varies with the thickness of the intrinsic layer in a PIN structure.Here,we interpret the anomalous absorption coefficient from the competition between recombination and drift for non-equilibrium carriers.Based on the Fokker-Planck theory,a non-equilibrium statistical model that describes the relationship between absorption coefficient and material thickness has been proposed.It could predict the experimental data well.Our results can give new ideas to design photoelectric devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62004218,61991441,and 61804176)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB01000000)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2021005).
文摘SiGe spheres with different diameters are successfully fabricated on a virtual SiGe template using a laser irradiation method.The results from scanning electron microscopy and micro-Raman spectroscopy reveal that the diameter and Ge composition of the SiGe spheres can be well controlled by adjusting the laser energy density.In addition,the transmission electron microscopy results show that Ge composition inside the SiGe spheres is almost uniform in a well-defined,nearly spherical outline.As a convenient method to prepare sphere-shaped SiGe micro/nanostructures with tunable Ge composition and size,this technique is expected to be useful for SiGe-based material growth and micro/optoelectronic device fabrication.
基金Supported by the National Natural Science Foundation of China(Grant Nos.62004218,61704008,61804176,and 61991441)Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant No.2021005)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB01000000)Jiangsu Science and Technology Plan(Grant No.BK20180255)supported by the Center for Clean Energy,Institute of Physics,Chinese Academy of Sciences。
文摘The contact characteristic between p-InP and metal plays an important role in InP-related optoelectronic and microelectronic device applications.We investigate the low-resistance Au/Pt/Ni and Au/Ni ohmic contacts to p-InP based on the solid phase regrowth principle.The lowest specific contact resistivity of Au(100 nm)/Pt(115 nm)/Ni(50 nm)can reach 2.64×10^(-6)Ω·cm^(2) after annealing at 380℃ for 1 min,while the contact characteristics of Au/Ni deteriorated after annealing from 340℃ to 480℃ for 1 min.The results of scanning electron microscopy,atomic force microscopy and x-ray photoelectron spectroscopy show that the Pt layer is an important factor in improving the contact characteristics.The Pt layer prevents the diffusion of In and Au,inhibits the formation of Au3In metal compounds,and prevents the deterioration of the ohmic contact.The metal structures and optimized annealing process is expected to be helpful for obtaining high-performance InP-related devices.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11574362 and 61704008)。
文摘We demonstrate that a low-temperature Ga N insertion layer could significantly improve the surface morphology of non-polar a-plane Ga N.The two key factors in improving the surface morphology of non-polar a-plane Ga N are growth temperature and growth time of the Ga N insertion layer.The root-mean-square roughness of a-plane Ga N is reduced by 75%compared to the sample without the Ga N insertion layer.Meanwhile,the Ga N insertion layer is also beneficial for improving crystal quality.This work provides a simple and effective method to improve the surface morphology of non-polar a-plane Ga N.
基金Supported by the National Natural Science Foundation of China(Grant Nos.61704008 and 11574362)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000).
文摘It is known that the p–n junction of an absorption region is a crucial part for power conversion efficiency of photovoltaic power converters.We fabricate four samples with different dopant concentrations in base layers.The dependences of power conversion efficiency and fill factor on input power are displayed by photocurrent–voltage measurement.Photoluminescence characteristics under open circuit and connected circuit conditions are also studied.It is found that the status of p–n junction matching is the critical factor in affecting the power conversion efficiency.In addition,series resistance of photovoltaic power converters impairs the efficiency especially at high input powers.Both the key factors need to be considered to obtain high efficiency,and this work provides promising guidance on designing photovoltaic power converters.
基金supported by the National Natural Science Foundation of China(Grant Nos.22278101,22068010,22168016,and 52365044)the Natural Science Foundation of Hainan Province(Grant Nos.2019RC142 and 519QN176)the Finance Science and Technology Project of Hainan Province(Grant No.ZDYF2020009).
文摘Novel and promising chloride ion batteries(CIBs)that can operate at room temperature have attracted great attentions,due to the sustainable chloride-containing resources and high theoretical energy density.To achieve the superior electrochemical properties of CIBs,the structure design of electrode materials is essential.Herein,2D NiAl-layered double hydroxide(NiAl-LDH)nanoarrays derived from Al2O3 are in-situ grafted to graphene(G)by atomic layer deposition(ALD)and hydrothermal method.The achieved NiAl-LDH@G hybrids with 2D NiAl-LDH arrays grown perpendicularly on graphene surface,can efficiently prevent the stacking of LDHs and enlarge specific surface area to provide more active sites.The NiAl-LDH@G cathode exhibits a maximum discharge capacity of 223.3 mA h g^(-1)and an excellent reversible capacity of 107 mA h g^(-1)over 500 cycles at 100 mA g^(-1)with a high coulombic efficiency around 96%,whereas pure NiAl-LDH has a discharge capacity of only 48.8 mA h g^(-1)and a coulombic efficiency(CE)of about 78%.More importantly,the NiAl-LDH@G electrode has a stable voltage at 1.9 V and an outstanding discharge capacity of higher than 72 mA h g^(-1)after 120 days.Additionally,XRD,XPS,and EDS have been employed to unveil the electrochemical reaction and Cl-storage mechanism of the NiAlLDH@G cathode in CIBs.This work opens a facile and reasonable way for improving electrochemical performance at anion-type rechargeable batteries in terms of cathode material design and mechanism interpretation.
基金National Key Research and Development Program of China(2024YFB2807901)Innovation Program for Quantum Science and Technology(2021ZD0302300)+3 种基金Strategic Priority Research Program of Chinese Academy of Sciences(XDB01000000)National Natural Science Foundation of China(61991441,62275117)Shenzhen Excellent Youth Program(RCYX20221008092900001)Synergetic Extreme Condition User Facility(SECUF,https://cstr.cn/31123.02.SECUF)。
文摘Ultra-compact spectrometers have attracted significant attention for their potential applications in portable systems for biomedical analysis,environmental monitoring,spectral analysis,and astronomical observation.In this work,we propose a miniaturized InGaAs-based extended short-wave infrared(eSWIR)spectrometer based on a single n-graded-p junction with voltage-tunable optical response characteristics in the range from 1600to 2100 nm.We combine this unique optical characteristic with a regression algorithm to realize the reconstruction of an unknown spectrum.The spectrometer achieves a high responsivity of 0.73 A/W at 1650 nm,and a low dark current density of 3.91×10^(-5)A/cm^2 at 200 K,corresponding to a calculated detectivity of1.69×10^(11)cm·Hz^(1/2)/W.Such spectrometers compatible with standard Ⅲ-Ⅴprocesses can offer a pathway to greatly promote the development of miniaturized spectrometers.
基金National Natural Science Foundation of China(11574362,61804176,61991441).
文摘An internal photoemission-based silicon photodetector detects light below the silicon bandgap at room temperature and can exhibit spectrally broad behavior,making it potentially suited to meet the need for a near-infrared pure Si photodetector.In this work,the implementation of a thin Au insertion layer into an ITO/n-Si Schottky photodetector can profoundly affect the barrier height and significantly improve the device performance.By fabricating a nanoscale thin Au layer and an ITO electrode on a silicon substrate,we achieve a well-behaved ITO/Au/n-Si Schottky diode with a record dark current density of 3.7×10^(−7) A/cm^(2) at−1 V and a high rectification ratio of 1.5×10^(8) at±1 V.Furthermore,the responsivity has been obviously improved without sacrificing the dark current performance of the device by decreasing the Au thickness.Such a silicon-based photodetector with an enhanced performance could be a promising strategy for the realization of a monolithic integrated pure silicon photodetector in optical communication.
基金supported by the National Natural Science Foundation of China(Grant Nos.22068010,22168016,51875318,52175341)the Natural Science Foundation of Hainan Province(Grant Nos.2019RC142,120RC454,519QN176)the Finance Science and technology project of Hainan Province(Grant No.ZDYF2020009).
文摘Electromagnetic pollution and heat dissipation problems are becoming increasingly worthy of attention due to the rapid development of electronic devices,which puts forward an urgent demand for microwave absorbers with excellent thermal management performance.Herein,high-performance Co/carbon nanofiber(Co/CNF)microwave absorbers with high thermal conductivity were fabricated by facile step-by-step method.The microwave absorption properties can be readily tuned by adjusting the content and size of Co nanoparticles through concentration gradient adsorption.Benefiting from the formation of dielectric and magnetic coupling network,Co/CNF composites possess intensive dipole polarization,interface polarization,and magnetic loss.The optimal Co/CNF composites exhibit outstanding microwave absorption performance with a minimum reflection loss(RL)of−53.0 dB at 11.44 GHz,and a maximum effective absorption bandwidth(EAB)of 5.5 GHz.In addition,the thermal conductivities of the Co/CNF-natural rubber(Co/CNF-NR)composites are significantly improved.This work may inspire the exploration of high-efficiency heat-conduction microwave absorbers based on CNF.
