The controllable synthesis of complicated nanostructures in advanced two-dimensional(2D)semiconductors,such as periodic regular hole arrays,is essential and remains immature.Here,we report a green,facile,highly contro...The controllable synthesis of complicated nanostructures in advanced two-dimensional(2D)semiconductors,such as periodic regular hole arrays,is essential and remains immature.Here,we report a green,facile,highly controlled synthetic method to efficiently pattern 2D semiconductors,such as periodic regular hexagonal-shaped hole arrays(HHA),in 2D-TMDs.Combining the production of artificial defect arrays through laser irradiation with anisotropic annealing etching,we created HHA with different arrangements,controlled hole sizes,and densities in bilayer WS_(2).Atomic force microscopy(AFM),Raman,photoluminescence(PL),and scanning transmission electron microscopy(STEM)characterization show that the 2D semiconductors have high quality with atomical clean and sharp edges as well as undamaged crystals in the unetched region.Furthermore,other nanostructures,such as nanoribbons and periodic regular triangular-shaped 2D-TMD arrays,can be fabricated.This kind of 2D semiconductors fabrication strategy is general and can be extended to a series of 2D materials.Density functional theory(DFT)calculations show that one WS_(2)molecule from the edges of the laser-irradiated holed region exhibits a robust etching activation,making selective etching at the artificial defects and the fabrication of regular 2D semiconductors possible.展开更多
Based on the self-terminating thermal oxidation-assisted wet etching technique,two kinds of enhancement mode Al_(2)O_(3)/GaN MOSFETs(metal-oxide-semiconductor field-effect transistors)separately with sapphire substrat...Based on the self-terminating thermal oxidation-assisted wet etching technique,two kinds of enhancement mode Al_(2)O_(3)/GaN MOSFETs(metal-oxide-semiconductor field-effect transistors)separately with sapphire substrate and Si sub-strate are prepared.It is found that the performance of sapphire substrate device is better than that of silicon substrate.Comparing these two devices,the maximum drain current of sapphire substrate device(401 mA/mm)is 1.76 times that of silicon substrate device(228 mA/mm),and the field-effect mobility(μ_(FEmax))of sapphire substrate device(176 cm^(2)/V·s)is 1.83 times that of silicon substrate device(96 cm^(2)/V·s).The conductive resistance of silicon substrate device is 21.2Ω-mm,while that of sapphire substrate device is only 15.2Ω·mm,which is 61%that of silicon substrate device.The significant difference in performance between sapphire substrate and Si substrate is related to the differences in interface and border trap near Al_(2)O_(3)/GaN interface.Experimental studies show that(i)interface/border trap density in the sapphire substrate device is one order of magnitude lower than in the Si substrate device,(ii)Both the border traps in Al_(2)O_(3) dielectric near Al_(2)O_(3)/GaN and the interface traps in Al_(2)O_(3)/GaN interface have a significantly effect on device channel mobility,and(iii)the properties of gallium nitride materials on different substrates are different due to wet etching.The research results in this work provide a reference for further optimizing the performances of silicon substrate devices.展开更多
Nickel nanometer catalyst thin films were prepared on SiO2/Si substrates using sputtering coater. The effects of ammonia pretreatment on the catalyst films from continuous film to the nanoparticles were investigated. ...Nickel nanometer catalyst thin films were prepared on SiO2/Si substrates using sputtering coater. The effects of ammonia pretreatment on the catalyst films from continuous film to the nanoparticles were investigated. The nanostructures of the Ni thin films as a function of the catalyst film original thickness, the pretreatment time and temperature were discussed. The optimum parameters of etching process were obtained, and the functional mechanism of ammonia was primarily analyzed. Scanning electron microscopy （SEM） and atomic force microscopy （AFM） were used to evaluate the obtained nanoparticles. It is demonstrated that the controlled size and density distribution of the nanoparticles can be achieved by employing ammonia etching method.展开更多
Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals tha...Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.展开更多
With surface- and bulk-micromachining, an 8 × 8 mirrors array is designed, fabricated and tested, which is based on electro-thermal actuators and can be addressed individually. The micromirror is square shaped, 4...With surface- and bulk-micromachining, an 8 × 8 mirrors array is designed, fabricated and tested, which is based on electro-thermal actuators and can be addressed individually. The micromirror is square shaped, 4-corner-actuated. Its dimension is 200 μm × 200 μm. The substrate below it is caved away to ensure a tilt at an angle as large as possible. To protect the etch-sensitive features on the front side of the wafer undamaged during wet deep silicon etch on the backside, the wax protective coating process is used. Mirror actuated by powering an alternative pair of heaters will tilt in 2-DOF. If its 4 cantilevers/heaters are powered synchronously, it will move in a piston mode. The effective arrays are more than 80% out of the three finished wafers. When the ramp voltage frequency applied to a pair of neighboring cantilevers is 5 Hz at 10 V, the average tilting angle can be ± 8°.展开更多
基金National Key R&D Program of the Ministry of Science and Technology of China,Grant/Award Number:2022YFA1203801The National Natural Science Foundation of China,Grant/Award Numbers:51991340,51991343,52221001,62174051+1 种基金The Hunan Key R&D Program Project,Grant/Award Number:2022GK2005Ningbo Natural Science Foundation,Grant/Award Number:2023J023。
文摘The controllable synthesis of complicated nanostructures in advanced two-dimensional(2D)semiconductors,such as periodic regular hole arrays,is essential and remains immature.Here,we report a green,facile,highly controlled synthetic method to efficiently pattern 2D semiconductors,such as periodic regular hexagonal-shaped hole arrays(HHA),in 2D-TMDs.Combining the production of artificial defect arrays through laser irradiation with anisotropic annealing etching,we created HHA with different arrangements,controlled hole sizes,and densities in bilayer WS_(2).Atomic force microscopy(AFM),Raman,photoluminescence(PL),and scanning transmission electron microscopy(STEM)characterization show that the 2D semiconductors have high quality with atomical clean and sharp edges as well as undamaged crystals in the unetched region.Furthermore,other nanostructures,such as nanoribbons and periodic regular triangular-shaped 2D-TMD arrays,can be fabricated.This kind of 2D semiconductors fabrication strategy is general and can be extended to a series of 2D materials.Density functional theory(DFT)calculations show that one WS_(2)molecule from the edges of the laser-irradiated holed region exhibits a robust etching activation,making selective etching at the artificial defects and the fabrication of regular 2D semiconductors possible.
基金Project supported by the Research on Key Techniques in Reliability of Low Power Sensor Chip for IOTIPS and the Technology Project of Headquarters,State Grid Corporation of China(Grant No.5700-202041397A-0-0-00).
文摘Based on the self-terminating thermal oxidation-assisted wet etching technique,two kinds of enhancement mode Al_(2)O_(3)/GaN MOSFETs(metal-oxide-semiconductor field-effect transistors)separately with sapphire substrate and Si sub-strate are prepared.It is found that the performance of sapphire substrate device is better than that of silicon substrate.Comparing these two devices,the maximum drain current of sapphire substrate device(401 mA/mm)is 1.76 times that of silicon substrate device(228 mA/mm),and the field-effect mobility(μ_(FEmax))of sapphire substrate device(176 cm^(2)/V·s)is 1.83 times that of silicon substrate device(96 cm^(2)/V·s).The conductive resistance of silicon substrate device is 21.2Ω-mm,while that of sapphire substrate device is only 15.2Ω·mm,which is 61%that of silicon substrate device.The significant difference in performance between sapphire substrate and Si substrate is related to the differences in interface and border trap near Al_(2)O_(3)/GaN interface.Experimental studies show that(i)interface/border trap density in the sapphire substrate device is one order of magnitude lower than in the Si substrate device,(ii)Both the border traps in Al_(2)O_(3) dielectric near Al_(2)O_(3)/GaN and the interface traps in Al_(2)O_(3)/GaN interface have a significantly effect on device channel mobility,and(iii)the properties of gallium nitride materials on different substrates are different due to wet etching.The research results in this work provide a reference for further optimizing the performances of silicon substrate devices.
基金Funded by the State Key Program of National Natural Science Foundation of China (No. 50435030)the National Natural Science Foundation of China (No. 50775104)
文摘Nickel nanometer catalyst thin films were prepared on SiO2/Si substrates using sputtering coater. The effects of ammonia pretreatment on the catalyst films from continuous film to the nanoparticles were investigated. The nanostructures of the Ni thin films as a function of the catalyst film original thickness, the pretreatment time and temperature were discussed. The optimum parameters of etching process were obtained, and the functional mechanism of ammonia was primarily analyzed. Scanning electron microscopy （SEM） and atomic force microscopy （AFM） were used to evaluate the obtained nanoparticles. It is demonstrated that the controlled size and density distribution of the nanoparticles can be achieved by employing ammonia etching method.
基金This work was partly financially supported by NEDO.
文摘Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.
文摘With surface- and bulk-micromachining, an 8 × 8 mirrors array is designed, fabricated and tested, which is based on electro-thermal actuators and can be addressed individually. The micromirror is square shaped, 4-corner-actuated. Its dimension is 200 μm × 200 μm. The substrate below it is caved away to ensure a tilt at an angle as large as possible. To protect the etch-sensitive features on the front side of the wafer undamaged during wet deep silicon etch on the backside, the wax protective coating process is used. Mirror actuated by powering an alternative pair of heaters will tilt in 2-DOF. If its 4 cantilevers/heaters are powered synchronously, it will move in a piston mode. The effective arrays are more than 80% out of the three finished wafers. When the ramp voltage frequency applied to a pair of neighboring cantilevers is 5 Hz at 10 V, the average tilting angle can be ± 8°.
