Perovskite materials have triggered a renewed interest in photovoltaic research in the recent years.They display crystal forms with 0D,1D and 2D,3D motifs,and several chemical forms,namely inorganic(titanates,rubidiat...Perovskite materials have triggered a renewed interest in photovoltaic research in the recent years.They display crystal forms with 0D,1D and 2D,3D motifs,and several chemical forms,namely inorganic(titanates,rubidiates,nobiates,tantalates etc.),organic/inorganic metal halides with single to multiple cations,and even organic polymer or quantum dot-infused hybrids.Each crystal type and chemical form are endowed with specific physicochemical,optical,electronic,and morphological properties.These unique properties render them suitable for targeted applications,namely photovoltaics,LEDs,photocatalysis/electrolysis/solar fuels/solar and Li-ion batteries,gas-sensors,ferroelectrics,capacitors,transistors and memristors,photodetectors,and lasers,for advanced quantum cryptography and outer space applications.At first,the crystal and material types,and physicochemical,morphological,and optoelectronic properties of perovskite materials are discussed.Particularly,we focus on those properties which cumulatively contribute to their application in the abovementioned fields.Simultaneously,a comprehensive discussion about the advances in each field is presented.Structure/property/application relationships with key advances demonstrate the versatility of perovskites in modern optoelectronic technologies.展开更多
Emerging memristive devices offer enormous advantages for applications such as non-volatile memories and inmemory computing(IMC),but there is a rising interest in using memristive technologies for security application...Emerging memristive devices offer enormous advantages for applications such as non-volatile memories and inmemory computing(IMC),but there is a rising interest in using memristive technologies for security applications in the era of internet of things(IoT).In this review article,for achieving secure hardware systems in IoT,lowpower design techniques based on emerging memristive technology for hardware security primitives/systems are presented.By reviewing the state-of-the-art in three highlighted memristive application areas,i.e.memristive non-volatile memory,memristive reconfigurable logic computing and memristive artificial intelligent computing,their application-level impacts on the novel implementations of secret key generation,crypto functions and machine learning attacks are explored,respectively.For the low-power security applications in IoT,it is essential to understand how to best realize cryptographic circuitry using memristive circuitries,and to assess the implications of memristive crypto implementations on security and to develop novel computing paradigms that will enhance their security.This review article aims to help researchers to explore security solutions,to analyze new possible threats and to develop corresponding protections for the secure hardware systems based on low-cost memristive circuit designs.展开更多
In this contribution,inspired by the excellent resource management and material transport function of leaf veins,the electrical transport function of metallized leaf veins is mimicked from the material transport funct...In this contribution,inspired by the excellent resource management and material transport function of leaf veins,the electrical transport function of metallized leaf veins is mimicked from the material transport function of the vein networks.By electroless copper plating on real leaf vein networks with copper thickness of only several hundred nanometre up to several micrometre,certain leaf veins can be converted to transparent conductive electrodes with an ultralow sheet resistance 100 times lower than that of state-of-the-art indium tin oxide thin films,combined with a broadband optical transmission of above 80%in the UV–VIS–IR range.Additionally,the resource efficiency of the vein-like electrode is characterized by the small amount of material needed to build up the networks and the low copper consumption during metallization.In particular,the high current density transport capability of the electrode of>6000 A cm^−2 was demonstrated.These superior properties of the vein-like structures inspire the design of high-performance transparent conductive electrodes without using critical materials and may significantly reduce the Ag consumption down to<10%of the current level for mass production of solar cells and will contribute greatly to the electrode for high power density concentrator solar cells,high power density Li-ion batteries,and supercapacitors.展开更多
We report on a fast and sensitive temperature sensor using a micro-structured or photonic crystal fiber interferometer with a high germanium doped fiber core. The wavelength sensitivity for temperature variation was a...We report on a fast and sensitive temperature sensor using a micro-structured or photonic crystal fiber interferometer with a high germanium doped fiber core. The wavelength sensitivity for temperature variation was as high as △λ/△T= 78 pm/℃ up to 500℃, which was 6 times more sensitive than the fiber Bragg grating temperature sensitivity of △λ/△TT= 13pm/℃ at 1550nm. The sensor device was investigated conceming the sensitivity characteristics and response time.展开更多
A curvature sensor based on an Fabry-Perot （FP） interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity le...A curvature sensor based on an Fabry-Perot （FP） interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/℃ to 0.89 pm/℃, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature.展开更多
Tip-enhanced Raman spectroscopy(TERS)is currently widely recognized as an essential but still emergent technique for exploring the nanoscale.However,our lack of comprehension of crucial parameters still limits its pot...Tip-enhanced Raman spectroscopy(TERS)is currently widely recognized as an essential but still emergent technique for exploring the nanoscale.However,our lack of comprehension of crucial parameters still limits its potential as a user-friendly analytical tool.The tip’s surface plasmon resonance,heating due to near-field temperature rise,and spatial resolution are undoubtedly three challenging experimental parameters to unravel.However,they are also the most fundamentally relevant parameters to explore,because they ultimately influence the state of the investigated molecule and consequently the probed signal.Here we propose a straightforward and purely experimental method to access quantitative information of the plasmon resonance and near-field temperature experienced exclusively by the molecules directly contributing to the TERS signal.The detailed near-field optical response,both at the molecular level and as a function of time,is evaluated using standard TERS experimental equipment by simultaneously probing the Stokes and anti-Stokes spectral intensities.Self-assembled 16-mercaptohexadodecanoic acid monolayers covalently bond to an ultra-flat gold surface were used as a demonstrator.Observation of blinking lines in the spectra also provides crucial information on the lateral resolution and indication of atomic-scale thermally induced morphological changes of the tip during the experiment.This study provides access to unprecedented molecular-level information on physical parameters that crucially affect experiments under TERS conditions.The study thereby improves the usability of TERS in day-to-day operation.The obtained information is of central importance for any experimental plasmonic investigation and for the application of TERS in the field of nanoscale thermometry.展开更多
Silica-based fiber tips are used in a variety of spectroscopic, micro- or nano-scopic optical sensor applications and photonic micro-devices. The miniaturization of optical sensor systems and the technical implementat...Silica-based fiber tips are used in a variety of spectroscopic, micro- or nano-scopic optical sensor applications and photonic micro-devices. The miniaturization of optical sensor systems and the technical implementation using optical fibers can provide new sensor designs with improved properties and functionality for new applications. The selective-etching of specifically doped silica fibers is a promising method in order to form complex photonic micro structures at the end or within fibers such as tips and cavities in various shapes useful for the all-fiber sensor and imaging applications. In the present study, we investigated the preparation of geometrically predefined, nanoscaled fiber tips by taking advantage of the dopant concentration profiles of highly doped step-index fibers. For this purpose, a gas phase etching process using hydrofluoric acid （HF） vapor was applied. The shaping of the fiber tips was based on very different etching rates as a result of the doping characteristics of specific optical fibers. Technological studies on the influence of the etching gas atmosphere on the temporal tip shaping and the final geometry were performed using undoped and doped silica fibers. The influence of the doping characteristics was investigated in phosphorus-, germanium-, fluorine- and boron-doped glass fibers. Narrow exposed as well as protected internal fiber tips in various shapes and tip radiuses down to less than 15 nm were achieved and characterized geometrically and topologically. For investigations into surface plasmon resonance effects, the fiber tips were coated with nanometer-sized silver layers by means of vapour deposition and finally subjected to an annealing treatment.展开更多
Growth temperature effects on the microstructure of Nb-doped BaTiO_(3) thin films of the composition BaTi_(0.98)Nb_(0.02)O_(3) are studied using X-ray diffraction and transmission electron microscopy(TEM).Reciprocal s...Growth temperature effects on the microstructure of Nb-doped BaTiO_(3) thin films of the composition BaTi_(0.98)Nb_(0.02)O_(3) are studied using X-ray diffraction and transmission electron microscopy(TEM).Reciprocal space maps and electron diffraction patterns show that the a-axis lattice parameter increases and the c-axis parameter decreases with increasing growth temperature,indicating a decrease of tetragonality.Bright-field TEM images show low and high densities of threading defects in films grown at low and high temperatures,respectively.The observations are discussed in terms of a hindering of the cubic-to-tetragonal phase transition by a high defect density and a high unit cell volume.展开更多
We evaluate the sensing properties of plasmonic waveguide sensors by calculating their resonant transmission spectra in different regions of the non-Hermitian eigenmode space.We elucidate the pitfalls of using modal d...We evaluate the sensing properties of plasmonic waveguide sensors by calculating their resonant transmission spectra in different regions of the non-Hermitian eigenmode space.We elucidate the pitfalls of using modal dispersion calculations in isolation to predict plasmonic sensor performance,which we address by using a simple model accounting for eigenmode excitation and propagation.Our transmission calculations show that resonant wavelength and spectral width crucially depend on the length of the sensing region,so that no single criterion obtained from modal dispersion calculations alone can be used as a proxy for sensitivity.Furthermore,we find that the optimal detection limits occur where directional coupling is supported,where the narrowest spectra occur.Such narrow spectral features can only be measured by filtering out all higher-order modes at the output,e.g.,via a single-mode waveguide.Our calculations also confirm a characteristic square root dependence of the eigenmode splitting with respect to the permittivity perturbation at the exceptional point,which we show can be identified through the sensor beat length at resonance.This work provides a convenient framework for designing and characterizing plasmonic waveguide sensors when comparing them with experimental measurements.展开更多
文摘Perovskite materials have triggered a renewed interest in photovoltaic research in the recent years.They display crystal forms with 0D,1D and 2D,3D motifs,and several chemical forms,namely inorganic(titanates,rubidiates,nobiates,tantalates etc.),organic/inorganic metal halides with single to multiple cations,and even organic polymer or quantum dot-infused hybrids.Each crystal type and chemical form are endowed with specific physicochemical,optical,electronic,and morphological properties.These unique properties render them suitable for targeted applications,namely photovoltaics,LEDs,photocatalysis/electrolysis/solar fuels/solar and Li-ion batteries,gas-sensors,ferroelectrics,capacitors,transistors and memristors,photodetectors,and lasers,for advanced quantum cryptography and outer space applications.At first,the crystal and material types,and physicochemical,morphological,and optoelectronic properties of perovskite materials are discussed.Particularly,we focus on those properties which cumulatively contribute to their application in the abovementioned fields.Simultaneously,a comprehensive discussion about the advances in each field is presented.Structure/property/application relationships with key advances demonstrate the versatility of perovskites in modern optoelectronic technologies.
基金supported by the DFG(German Research Foundation)Priority Program Nano Security,Project MemCrypto(Projektnummer 439827659/funding id DU 1896/2–1,PO 1220/15–1)the funding by the Fraunhofer Internal Programs under Grant No.Attract 600768。
文摘Emerging memristive devices offer enormous advantages for applications such as non-volatile memories and inmemory computing(IMC),but there is a rising interest in using memristive technologies for security applications in the era of internet of things(IoT).In this review article,for achieving secure hardware systems in IoT,lowpower design techniques based on emerging memristive technology for hardware security primitives/systems are presented.By reviewing the state-of-the-art in three highlighted memristive application areas,i.e.memristive non-volatile memory,memristive reconfigurable logic computing and memristive artificial intelligent computing,their application-level impacts on the novel implementations of secret key generation,crypto functions and machine learning attacks are explored,respectively.For the low-power security applications in IoT,it is essential to understand how to best realize cryptographic circuitry using memristive circuitries,and to assess the implications of memristive crypto implementations on security and to develop novel computing paradigms that will enhance their security.This review article aims to help researchers to explore security solutions,to analyze new possible threats and to develop corresponding protections for the secure hardware systems based on low-cost memristive circuit designs.
基金the financial support from the BMWi within the projects TherSiTex(ZF4006804PR5)TexCool(ZF4006814BA8)
文摘In this contribution,inspired by the excellent resource management and material transport function of leaf veins,the electrical transport function of metallized leaf veins is mimicked from the material transport function of the vein networks.By electroless copper plating on real leaf vein networks with copper thickness of only several hundred nanometre up to several micrometre,certain leaf veins can be converted to transparent conductive electrodes with an ultralow sheet resistance 100 times lower than that of state-of-the-art indium tin oxide thin films,combined with a broadband optical transmission of above 80%in the UV–VIS–IR range.Additionally,the resource efficiency of the vein-like electrode is characterized by the small amount of material needed to build up the networks and the low copper consumption during metallization.In particular,the high current density transport capability of the electrode of>6000 A cm^−2 was demonstrated.These superior properties of the vein-like structures inspire the design of high-performance transparent conductive electrodes without using critical materials and may significantly reduce the Ag consumption down to<10%of the current level for mass production of solar cells and will contribute greatly to the electrode for high power density concentrator solar cells,high power density Li-ion batteries,and supercapacitors.
文摘We report on a fast and sensitive temperature sensor using a micro-structured or photonic crystal fiber interferometer with a high germanium doped fiber core. The wavelength sensitivity for temperature variation was as high as △λ/△T= 78 pm/℃ up to 500℃, which was 6 times more sensitive than the fiber Bragg grating temperature sensitivity of △λ/△TT= 13pm/℃ at 1550nm. The sensor device was investigated conceming the sensitivity characteristics and response time.
文摘A curvature sensor based on an Fabry-Perot （FP） interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/℃ to 0.89 pm/℃, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature.
基金the support via the German Research Foundation DFG(CRC 1375 NOA)the financial support of the NSERC and the DFG(Project number 364549901-TRR 234 CataLight(C1)).
文摘Tip-enhanced Raman spectroscopy(TERS)is currently widely recognized as an essential but still emergent technique for exploring the nanoscale.However,our lack of comprehension of crucial parameters still limits its potential as a user-friendly analytical tool.The tip’s surface plasmon resonance,heating due to near-field temperature rise,and spatial resolution are undoubtedly three challenging experimental parameters to unravel.However,they are also the most fundamentally relevant parameters to explore,because they ultimately influence the state of the investigated molecule and consequently the probed signal.Here we propose a straightforward and purely experimental method to access quantitative information of the plasmon resonance and near-field temperature experienced exclusively by the molecules directly contributing to the TERS signal.The detailed near-field optical response,both at the molecular level and as a function of time,is evaluated using standard TERS experimental equipment by simultaneously probing the Stokes and anti-Stokes spectral intensities.Self-assembled 16-mercaptohexadodecanoic acid monolayers covalently bond to an ultra-flat gold surface were used as a demonstrator.Observation of blinking lines in the spectra also provides crucial information on the lateral resolution and indication of atomic-scale thermally induced morphological changes of the tip during the experiment.This study provides access to unprecedented molecular-level information on physical parameters that crucially affect experiments under TERS conditions.The study thereby improves the usability of TERS in day-to-day operation.The obtained information is of central importance for any experimental plasmonic investigation and for the application of TERS in the field of nanoscale thermometry.
文摘Silica-based fiber tips are used in a variety of spectroscopic, micro- or nano-scopic optical sensor applications and photonic micro-devices. The miniaturization of optical sensor systems and the technical implementation using optical fibers can provide new sensor designs with improved properties and functionality for new applications. The selective-etching of specifically doped silica fibers is a promising method in order to form complex photonic micro structures at the end or within fibers such as tips and cavities in various shapes useful for the all-fiber sensor and imaging applications. In the present study, we investigated the preparation of geometrically predefined, nanoscaled fiber tips by taking advantage of the dopant concentration profiles of highly doped step-index fibers. For this purpose, a gas phase etching process using hydrofluoric acid （HF） vapor was applied. The shaping of the fiber tips was based on very different etching rates as a result of the doping characteristics of specific optical fibers. Technological studies on the influence of the etching gas atmosphere on the temporal tip shaping and the final geometry were performed using undoped and doped silica fibers. The influence of the doping characteristics was investigated in phosphorus-, germanium-, fluorine- and boron-doped glass fibers. Narrow exposed as well as protected internal fiber tips in various shapes and tip radiuses down to less than 15 nm were achieved and characterized geometrically and topologically. For investigations into surface plasmon resonance effects, the fiber tips were coated with nanometer-sized silver layers by means of vapour deposition and finally subjected to an annealing treatment.
基金supported by the Korea Research Council of Fundamental Science and Technology(KRCF)through a Basic Research Project managed by the Korea Research Institute of Standards and Science(KRISS)Support was also given by the Natural Science Foundation of China(Grant No.61271127).
文摘Growth temperature effects on the microstructure of Nb-doped BaTiO_(3) thin films of the composition BaTi_(0.98)Nb_(0.02)O_(3) are studied using X-ray diffraction and transmission electron microscopy(TEM).Reciprocal space maps and electron diffraction patterns show that the a-axis lattice parameter increases and the c-axis parameter decreases with increasing growth temperature,indicating a decrease of tetragonality.Bright-field TEM images show low and high densities of threading defects in films grown at low and high temperatures,respectively.The observations are discussed in terms of a hindering of the cubic-to-tetragonal phase transition by a high defect density and a high unit cell volume.
文摘We evaluate the sensing properties of plasmonic waveguide sensors by calculating their resonant transmission spectra in different regions of the non-Hermitian eigenmode space.We elucidate the pitfalls of using modal dispersion calculations in isolation to predict plasmonic sensor performance,which we address by using a simple model accounting for eigenmode excitation and propagation.Our transmission calculations show that resonant wavelength and spectral width crucially depend on the length of the sensing region,so that no single criterion obtained from modal dispersion calculations alone can be used as a proxy for sensitivity.Furthermore,we find that the optimal detection limits occur where directional coupling is supported,where the narrowest spectra occur.Such narrow spectral features can only be measured by filtering out all higher-order modes at the output,e.g.,via a single-mode waveguide.Our calculations also confirm a characteristic square root dependence of the eigenmode splitting with respect to the permittivity perturbation at the exceptional point,which we show can be identified through the sensor beat length at resonance.This work provides a convenient framework for designing and characterizing plasmonic waveguide sensors when comparing them with experimental measurements.
