This paper describes a novel,system-level design methodology based on a genetic algorithm(GA)using freeform geometries for microelectromechanical systems(MEMS)devices.The proposed method can concurrently design and co...This paper describes a novel,system-level design methodology based on a genetic algorithm(GA)using freeform geometries for microelectromechanical systems(MEMS)devices.The proposed method can concurrently design and co-optimize the electronic and mechanical parts of a MEMS device comprising freeform geometries to achieve a better system performance,i.e.,a high sensitivity,a good system stability,and large fabrication tolerances.Also,the introduction of freeform geometries allows higher degrees of freedom in the design process,improving the diversity and potentially the performance of the MEMS devices.A MEMS accelerometer comprising a freeform mechanical motion preamplifier in a closed-loop control system is presented to demonstrate the effectiveness of the design approach.The optimization process shows the main figure-of-merit(FOM)is improved by 195%.In the mechanical component alone(open-loop system),the product of sensitivity and bandwidth has improved by 151%,with sensitivity increasing by 276%.For closed-loop performance,there is an improvement of 120%for the ratio of open and closed-loop displacements.The product of sensitivity and bandwidth is improved by 27%in the closed-loop system.Excellent immunities to fabrication errors and parameter mismatch are achieved.Experiments show that the displacement of the MEMS accelerometer in the closed-loop system decreased by 86%with 4.85 V feedback voltage compared with that in the open-loop system under a 1 g 100 Hz acceleration input.The static and dynamic nonlinearities in the closed-loop system are improved by 64%and 61%,respectively,compared with those in the open-loop system,in the±1 g acceleration input range.Besides,the closed-loop system improves the cross-axis sensitivity by 18.43%,compared with that in the open-loop system.It is the first time a closed-loop system for a MEMS accelerometer comprising a mechanical motion preamplifier is successfully implemented experimentally.展开更多
Buried channel array transistors enable fast and high-density integrated devices.The depth of the PN junction and carrier dynamics at the depletion layer in silicon wafers have a crucial influence on their performance...Buried channel array transistors enable fast and high-density integrated devices.The depth of the PN junction and carrier dynamics at the depletion layer in silicon wafers have a crucial influence on their performance and reliability.Therefore,rapid and non-contact/non-destructive inspection tools are necessary to accelerate the semiconductor industry.Despite the great efforts in this field,realizing a technique to probe the junction depth and carrier dynamics at the PN junction inside wafers remains challenging.Herein,we propose a new approach to access PN junctions embedded in wafers using terahertz(THz)emission spectroscopy.THz emission measurements and simulations demonstrate that the amplitude and polarity of THz emissions reflect the junction depth and carrier dynamics at the PN junctions.It allows us to evaluate the junction depth non-destructively with nanometer-scale accuracy,surpassing the limits of traditional techniques.Laser-induced THz emission spectroscopy is a promising method for the sensitive and non-contact/non-destructive evaluation of Si wafers and will benefit the modern semiconductor industry.展开更多
Exploring advanced thermoelectric materials,especially flexible thermoelectric fibers,is promising for wearable devices.The thermoelectric properties of these fibers are evaluated using the figure of merit ZT value.Ho...Exploring advanced thermoelectric materials,especially flexible thermoelectric fibers,is promising for wearable devices.The thermoelectric properties of these fibers are evaluated using the figure of merit ZT value.However,there is a lack of empirical research on the properties of microscale thermoelectric fibers,necessitating the development of precise measurement methods.In addition,since the properties of micro-and nanofiber materials can be affected by the microstructure,separate measurements of electrical conductivity,Seebeck coefficient,and thermal conductivity before calculating the ZT values can lead to large errors in the final calculations.In this study,Bi_(2)Te_(2.7)Se_(0.3) thermoelectric fibers are prepared and measured by using a thermally drawn method and an in situ method,respectively.The in situ measurements are carried out using a self-developed instrument capable of measuring temperatures from room temperature up to 1,200 K,suitable for sample sizes ranging from micro-to nanoscale.The uncertainty of the measurement exhibits less than 6.36%.The results indicate that the thermal drawing process influences crystal growth,enhancing the Seebeck coefficient and reducing electrical conductivity and thermal conductivity.Moreover,the accuracy of the measurement method is verified by pure Pt wire.The integrated in situ measurement effectively reduces experimental errors due to sample differences when calculating parameters for multiple samples measured individually,and the maximum error that can be reduced is 19.5%.This research contributes a practical measurement method of thermoelectric fibers and advances the development of wearable thermoelectric devices.展开更多
CONSPECTUS:Organic hole-transporting materials(HTMs)are of importance in the progress of new-generation photovoltaics,notably in perovskite solar cells(PSCs),solid-state dye-sensitized solar cells(sDSCs),and organic s...CONSPECTUS:Organic hole-transporting materials(HTMs)are of importance in the progress of new-generation photovoltaics,notably in perovskite solar cells(PSCs),solid-state dye-sensitized solar cells(sDSCs),and organic solar cells(OSCs).These materials play a vital role in hole collection and transportation,significantly impacting the power conversion efficiency(PCE)and overall stability of photovoltaic devices.The emergence of spiro(fluorene-9,9′-xanthene)(SFX)as a novel building block for organic HTMs has gained considerable attention in the field of photovoltaics.Its facile one-pot synthetic approach,straightforward purification,and physiochemical properties over the prototype HTM spiro-OMeTAD have positioned SFX as a highly attractive alternative.In this Account,we present a comprehensive and in-depth summary of our research work,focusing on the advancements in SFX-based organic HTMs in photovoltaic devices with a particular emphasis on PSCs and sDSCs.Several key objectives of our research have been focused on exploring strategies to improve the properties of SFX-based HTMs.(i)One of the critical aspects we have addressed is the improvement of film quality.By carefully designing the molecular structure and employing suitable synthetic approaches,we have achieved HTMs with excellent film-forming ability,resulting in uniform and smooth films over large areas.This achievement is pivotal in ensuring the reproducibility and efficiency of photovoltaic devices.Furthermore,(ii)our investigations have led to an improvement in hole mobility within the HTMs.Through molecular engineering,such as increasing the molecular conjugation and introducing multiple SFX units,we have demonstrated enhanced charge-carrier mobility.This advancement plays a crucial role in minimizing charge recombination losses and improving the overall device efficiency.Additionally,(iii)we have explored the concept of defect passivation in SFX-based HTMs.By incorporating Lewis base structures,such as pyridine groups,we have successfully coordinated to Pb2+in the perovskite layer,resulting in a passivation of surface defects.This defect passivation contributes to better stability and enhanced device performance.Throughout our review,we highlighted the potential and opportunities achieved through these steps.The combination of enhanced film quality,improved hole mobility,and defect passivation resulted in remarkable photovoltaic performance.Our findings have demonstrated promising short-circuit current densities,open-circuit voltages,fill factors,and PCEs,with some HTMs even outperforming the widely used spiro-OMeTAD.We believe that this review will not only provide a better understanding of SFX-based HTMs but also open new avenues for enhancing the performance of organic HTMs in photovoltaic and other organic electronic devices.By providing unique perspectives and exploring different strategies,we aim to inspire ongoing advancements in photovoltaic technologies and organic electronics.Meanwhile,the success of SFX-based HTMs in improving photovoltaic device performance holds great promise for the continued development of efficient and stable photovoltaic devices in the years to come.展开更多
基金supported by The Science and Technology Development Fund,Macao SAR(FDCT),004/2023/SKLThe Science and Technology Development Fund,Macao SAR(FDCT),0087/2023/ITP2.
文摘This paper describes a novel,system-level design methodology based on a genetic algorithm(GA)using freeform geometries for microelectromechanical systems(MEMS)devices.The proposed method can concurrently design and co-optimize the electronic and mechanical parts of a MEMS device comprising freeform geometries to achieve a better system performance,i.e.,a high sensitivity,a good system stability,and large fabrication tolerances.Also,the introduction of freeform geometries allows higher degrees of freedom in the design process,improving the diversity and potentially the performance of the MEMS devices.A MEMS accelerometer comprising a freeform mechanical motion preamplifier in a closed-loop control system is presented to demonstrate the effectiveness of the design approach.The optimization process shows the main figure-of-merit(FOM)is improved by 195%.In the mechanical component alone(open-loop system),the product of sensitivity and bandwidth has improved by 151%,with sensitivity increasing by 276%.For closed-loop performance,there is an improvement of 120%for the ratio of open and closed-loop displacements.The product of sensitivity and bandwidth is improved by 27%in the closed-loop system.Excellent immunities to fabrication errors and parameter mismatch are achieved.Experiments show that the displacement of the MEMS accelerometer in the closed-loop system decreased by 86%with 4.85 V feedback voltage compared with that in the open-loop system under a 1 g 100 Hz acceleration input.The static and dynamic nonlinearities in the closed-loop system are improved by 64%and 61%,respectively,compared with those in the open-loop system,in the±1 g acceleration input range.Besides,the closed-loop system improves the cross-axis sensitivity by 18.43%,compared with that in the open-loop system.It is the first time a closed-loop system for a MEMS accelerometer comprising a mechanical motion preamplifier is successfully implemented experimentally.
基金M.T.acknowledges support by JSPS KAKENHI Grant No.JP23H00184F.M.acknowledges support in part by Grantin-Aid for JSPS Fellows Grant No.23KJ1475 and Program for Leading Graduate Schools:“Interactive Materials Science Cadet Program”.
文摘Buried channel array transistors enable fast and high-density integrated devices.The depth of the PN junction and carrier dynamics at the depletion layer in silicon wafers have a crucial influence on their performance and reliability.Therefore,rapid and non-contact/non-destructive inspection tools are necessary to accelerate the semiconductor industry.Despite the great efforts in this field,realizing a technique to probe the junction depth and carrier dynamics at the PN junction inside wafers remains challenging.Herein,we propose a new approach to access PN junctions embedded in wafers using terahertz(THz)emission spectroscopy.THz emission measurements and simulations demonstrate that the amplitude and polarity of THz emissions reflect the junction depth and carrier dynamics at the PN junctions.It allows us to evaluate the junction depth non-destructively with nanometer-scale accuracy,surpassing the limits of traditional techniques.Laser-induced THz emission spectroscopy is a promising method for the sensitive and non-contact/non-destructive evaluation of Si wafers and will benefit the modern semiconductor industry.
基金supported by the National Key Research and Development Program of China(2023YFB3809800)the National Natural Science Foundation of China(52172249)+3 种基金the Scientific Instrument Developing Project of the Chinese Academy of Sciences(YJKYYQ20200017)the Chinese Academy of Sciences Talents Program(E2290701)the Jiangsu Province Talents Program(JSSCRC2023545)the Special Fund Project of Carbon Peaking Carbon Neutrality Science and Technology Innovation of Jiangsu Province(BE2022011)。
文摘Exploring advanced thermoelectric materials,especially flexible thermoelectric fibers,is promising for wearable devices.The thermoelectric properties of these fibers are evaluated using the figure of merit ZT value.However,there is a lack of empirical research on the properties of microscale thermoelectric fibers,necessitating the development of precise measurement methods.In addition,since the properties of micro-and nanofiber materials can be affected by the microstructure,separate measurements of electrical conductivity,Seebeck coefficient,and thermal conductivity before calculating the ZT values can lead to large errors in the final calculations.In this study,Bi_(2)Te_(2.7)Se_(0.3) thermoelectric fibers are prepared and measured by using a thermally drawn method and an in situ method,respectively.The in situ measurements are carried out using a self-developed instrument capable of measuring temperatures from room temperature up to 1,200 K,suitable for sample sizes ranging from micro-to nanoscale.The uncertainty of the measurement exhibits less than 6.36%.The results indicate that the thermal drawing process influences crystal growth,enhancing the Seebeck coefficient and reducing electrical conductivity and thermal conductivity.Moreover,the accuracy of the measurement method is verified by pure Pt wire.The integrated in situ measurement effectively reduces experimental errors due to sample differences when calculating parameters for multiple samples measured individually,and the maximum error that can be reduced is 19.5%.This research contributes a practical measurement method of thermoelectric fibers and advances the development of wearable thermoelectric devices.
基金supported by the National Natural Science Foundation of China(Grant No.22279059)the Fundamental Research Funds for the Central Universities(No.30921011106,30923011030)the start-up funding from the NJUST.
文摘CONSPECTUS:Organic hole-transporting materials(HTMs)are of importance in the progress of new-generation photovoltaics,notably in perovskite solar cells(PSCs),solid-state dye-sensitized solar cells(sDSCs),and organic solar cells(OSCs).These materials play a vital role in hole collection and transportation,significantly impacting the power conversion efficiency(PCE)and overall stability of photovoltaic devices.The emergence of spiro(fluorene-9,9′-xanthene)(SFX)as a novel building block for organic HTMs has gained considerable attention in the field of photovoltaics.Its facile one-pot synthetic approach,straightforward purification,and physiochemical properties over the prototype HTM spiro-OMeTAD have positioned SFX as a highly attractive alternative.In this Account,we present a comprehensive and in-depth summary of our research work,focusing on the advancements in SFX-based organic HTMs in photovoltaic devices with a particular emphasis on PSCs and sDSCs.Several key objectives of our research have been focused on exploring strategies to improve the properties of SFX-based HTMs.(i)One of the critical aspects we have addressed is the improvement of film quality.By carefully designing the molecular structure and employing suitable synthetic approaches,we have achieved HTMs with excellent film-forming ability,resulting in uniform and smooth films over large areas.This achievement is pivotal in ensuring the reproducibility and efficiency of photovoltaic devices.Furthermore,(ii)our investigations have led to an improvement in hole mobility within the HTMs.Through molecular engineering,such as increasing the molecular conjugation and introducing multiple SFX units,we have demonstrated enhanced charge-carrier mobility.This advancement plays a crucial role in minimizing charge recombination losses and improving the overall device efficiency.Additionally,(iii)we have explored the concept of defect passivation in SFX-based HTMs.By incorporating Lewis base structures,such as pyridine groups,we have successfully coordinated to Pb2+in the perovskite layer,resulting in a passivation of surface defects.This defect passivation contributes to better stability and enhanced device performance.Throughout our review,we highlighted the potential and opportunities achieved through these steps.The combination of enhanced film quality,improved hole mobility,and defect passivation resulted in remarkable photovoltaic performance.Our findings have demonstrated promising short-circuit current densities,open-circuit voltages,fill factors,and PCEs,with some HTMs even outperforming the widely used spiro-OMeTAD.We believe that this review will not only provide a better understanding of SFX-based HTMs but also open new avenues for enhancing the performance of organic HTMs in photovoltaic and other organic electronic devices.By providing unique perspectives and exploring different strategies,we aim to inspire ongoing advancements in photovoltaic technologies and organic electronics.Meanwhile,the success of SFX-based HTMs in improving photovoltaic device performance holds great promise for the continued development of efficient and stable photovoltaic devices in the years to come.
