Nanomechanical photothermal sensing has significantly advanced single-molecule/particle microscopy and spectroscopy,and infrared detection.In this approach,the nanomechanical resonator detects shifts in resonant frequ...Nanomechanical photothermal sensing has significantly advanced single-molecule/particle microscopy and spectroscopy,and infrared detection.In this approach,the nanomechanical resonator detects shifts in resonant frequency due to photothermal heating.However,the relationship between photothermal sensitivity,response time,and resonator design has not been fully explored.This paper compares three resonator types-strings,drumheads,and trampolines-to explore this relationship.Through theoretical modeling,experimental validation,and finite element method simulations,we find that strings offer the highest sensitivity(with a noise equivalent power of 280 fW/Hz^(1/2)for strings made of silicon nitride),while drumheads exhibit the fastest thermal response.The study reveals that photothermal sensitivity correlates with the average temperature rise and not the peak temperature.Finally,the impact of photothermal back-action is discussed,which can be a major source of frequency instability.This work clarifies the performance differences and limits among resonator designs and guides the development of advanced nanomechanical photothermal sensors,benefiting a wide range of applications.展开更多
This work investigates in-depth the effects of variation of the compositional ratio of the absorber layer in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Electrical simulations were carried out in order to propose the m...This work investigates in-depth the effects of variation of the compositional ratio of the absorber layer in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Electrical simulations were carried out in order to propose the most suitable gallium double-grading profile for the high efficiency devices. To keep the model as close as possible to the real behavior of the thin film solar cell a trap model was implemented to describe the bulk defects in the absorber layer. The performance of a solar cell with a standard CIGS layer thickness (2 μm) exhibits a strong dependence on the front grading height (decreasing band gap toward the middle of the CIGS layer). An absolute gain in the efficiency (higher than 1%) is observed by a front grading height of 0.22. Moreover, simulation results show that the position of the plateau (the region characterized by the minimum band gap) should be accurately positioned at a compositional ratio of 20% Ga and 80% In, which corresponds to the region where a lower bulk defect density is expected. The developed model demonstrates that the length of the plateau is not playing a relevant role, causing just a slight change in the solar cell performances. Devices with different absorber layer thicknesses were simulated. The highest efficiency is obtained for a CIGS thin film with thicknesses between 0.8 and 1.1 μm.展开更多
Owing to their higher intrinsic electrical conductivity and chemical stability with respect to their oxide counterparts, nanostructured metal sulfides are expected to revive materials for resistive chemical sensor app...Owing to their higher intrinsic electrical conductivity and chemical stability with respect to their oxide counterparts, nanostructured metal sulfides are expected to revive materials for resistive chemical sensor applications. Herein, we explore the gas sensing behavior of WS2 nanowire-nanoflake hybrid materials and demonstrate their excellent sensitivity （0.043 ppm-1） as well as high selectivity towards H2S relative to CO, NH~, H2, and NO （with corresponding sensitivities of 0.002, 0.0074, 0.0002, and 0.0046 pprn-1, respectively）. Gas response measurements, complemented with the results of X-ray photoelectron spectroscopy analysis and first-principles calculations based on density functional theory, suggest that the intrinsic electronic properties of pristine WS2 alone are not sufficient to explain the observed high sensitivity towards H2S. A major role in this behavior is also played by O doping in the S sites of the WS2 lattice. The results of the present study open up new avenues for the use of transition metal disulfide nanomaterials as effective alternatives to metal oxides in future applications for industrial process control, security, and health and environmental safety.展开更多
A simple and cost-effective method for the patterning and fabrication of soft polymer microactuators integrated with morphological computation is presented.The microactuators combine conducting polymers to provide the...A simple and cost-effective method for the patterning and fabrication of soft polymer microactuators integrated with morphological computation is presented.The microactuators combine conducting polymers to provide the actuation,with spatially designed structures for a morphologically controlled,user-defined actuation.Soft lithography is employed to pattern and fabricate polydimethylsiloxane layers with geometrical pattern,for use as a construction element in the microactuators.These microactuators could obtain multiple bending motions from a single fabrication process depending on the morphological pattern defined in the final step.Instead of fabricating via conventional photolithography route,which involves multiple steps with different chromium photomasks,this new method uses only one single design template to produce geometrically patterned layers,which are then specifically cut to obtain multiple device designs.The desired design of the actuator is decided in the final step of fabrication.The resulting microactuators generate motions such as a spiral,screw,and tube,using a single design template.展开更多
Optical resonators are essential for fundamental science,applications in sensing and metrology,particle cooling,and quantum information processing.Cavities can significantly enhance interactions between light and matt...Optical resonators are essential for fundamental science,applications in sensing and metrology,particle cooling,and quantum information processing.Cavities can significantly enhance interactions between light and matter.For many applications they perform this task best if the mode confinement is tight and the photon lifetime is long.Free access to the mode center is important in the design to admit atoms,molecules,nanoparticles,or solids into the light field.Here,we demonstrate how to machine microcavity arrays of extremely high quality in pristine silicon.Etched to an almost perfect parabolic shape with a surface roughness on the level of 2A and coated to a finesse exceeding F=500,000,these new devices can have lengths below 17μm,confining the photons to 5μm waists in a mode volume of 88λ^(3).Extending the cavity length to 150μm,on the order of the radius of curvature,in a symmetric mirror configuration yields a waist smaller than 7μm,with photon lifetimes exceeding 64 ns.Parallelized cleanroom fabrication delivers an entire microcavity array in a single process.Photolithographic precision furthermore yields alignment structures that result in mechanically robust,pre-aligned,symmetric microcavity arrays,representing a lightmatter interface with unprecedented performance.展开更多
Long-wave infrared(LWIR, 8–14 μm) photonics is a rapidly growing research field within the mid-IR with applications in molecular spectroscopy and optical free-space communication. LWIR applications are often address...Long-wave infrared(LWIR, 8–14 μm) photonics is a rapidly growing research field within the mid-IR with applications in molecular spectroscopy and optical free-space communication. LWIR applications are often addressed using rather bulky tabletop-sized free-space optical systems, preventing advanced photonic applications,such as rapid-time-scale experiments. Here, device miniaturization into photonic integrated circuits(PICs) with maintained optical capabilities is key to revolutionize mid-IR photonics. Subwavelength mode confinement in plasmonic structures enabled such miniaturization approaches in the visible-to-near-IR spectral range. However,adopting plasmonics for the LWIR needs suitable low-loss and-dispersion materials with compatible integration strategies to existing mid-IR technology. In this paper, we further unlock the field of LWIR/mid-IR PICs by combining photolithographic patterning of organic polymers with dielectric-loaded surface plasmon polariton(DLSPP) waveguides. In particular, polyethylene shows favorable optical properties, including low refractive index and broad transparency between ~2 μm and 200 μm. We investigate the whole value chain, including design, fabrication, and characterization of polyethylene-based DLSPP waveguides and demonstrate their first-time plasmonic operation and mode guiding capabilities along S-bend structures. Low bending losses of ~1.3 d B and straight-section propagation lengths of ~1 mm, pave the way for unprecedented complex on-chip mid-IR photonic devices. Moreover, DLSPPs allow full control of the mode parameters(propagation length and guiding capabilities) for precisely addressing advanced sensing and telecommunication applications with chip-scale devices.展开更多
基金funding from the Novo Nordisk Foundation under project MASMONADE with project number NNF22OC0077964,and from the European Innovation Council under the European Union’s Horizon Europe Transition Open program(Grant agreement:101058711-NEMILIES).
文摘Nanomechanical photothermal sensing has significantly advanced single-molecule/particle microscopy and spectroscopy,and infrared detection.In this approach,the nanomechanical resonator detects shifts in resonant frequency due to photothermal heating.However,the relationship between photothermal sensitivity,response time,and resonator design has not been fully explored.This paper compares three resonator types-strings,drumheads,and trampolines-to explore this relationship.Through theoretical modeling,experimental validation,and finite element method simulations,we find that strings offer the highest sensitivity(with a noise equivalent power of 280 fW/Hz^(1/2)for strings made of silicon nitride),while drumheads exhibit the fastest thermal response.The study reveals that photothermal sensitivity correlates with the average temperature rise and not the peak temperature.Finally,the impact of photothermal back-action is discussed,which can be a major source of frequency instability.This work clarifies the performance differences and limits among resonator designs and guides the development of advanced nanomechanical photothermal sensors,benefiting a wide range of applications.
文摘This work investigates in-depth the effects of variation of the compositional ratio of the absorber layer in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Electrical simulations were carried out in order to propose the most suitable gallium double-grading profile for the high efficiency devices. To keep the model as close as possible to the real behavior of the thin film solar cell a trap model was implemented to describe the bulk defects in the absorber layer. The performance of a solar cell with a standard CIGS layer thickness (2 μm) exhibits a strong dependence on the front grading height (decreasing band gap toward the middle of the CIGS layer). An absolute gain in the efficiency (higher than 1%) is observed by a front grading height of 0.22. Moreover, simulation results show that the position of the plateau (the region characterized by the minimum band gap) should be accurately positioned at a compositional ratio of 20% Ga and 80% In, which corresponds to the region where a lower bulk defect density is expected. The developed model demonstrates that the length of the plateau is not playing a relevant role, causing just a slight change in the solar cell performances. Devices with different absorber layer thicknesses were simulated. The highest efficiency is obtained for a CIGS thin film with thicknesses between 0.8 and 1.1 μm.
文摘Owing to their higher intrinsic electrical conductivity and chemical stability with respect to their oxide counterparts, nanostructured metal sulfides are expected to revive materials for resistive chemical sensor applications. Herein, we explore the gas sensing behavior of WS2 nanowire-nanoflake hybrid materials and demonstrate their excellent sensitivity （0.043 ppm-1） as well as high selectivity towards H2S relative to CO, NH~, H2, and NO （with corresponding sensitivities of 0.002, 0.0074, 0.0002, and 0.0046 pprn-1, respectively）. Gas response measurements, complemented with the results of X-ray photoelectron spectroscopy analysis and first-principles calculations based on density functional theory, suggest that the intrinsic electronic properties of pristine WS2 alone are not sufficient to explain the observed high sensitivity towards H2S. A major role in this behavior is also played by O doping in the S sites of the WS2 lattice. The results of the present study open up new avenues for the use of transition metal disulfide nanomaterials as effective alternatives to metal oxides in future applications for industrial process control, security, and health and environmental safety.
基金the EU Marie Sklodowska-Curie Actions Initial Training Network MICACT(641822)the Swedish Research Council(2014-3079)for their financial support.
文摘A simple and cost-effective method for the patterning and fabrication of soft polymer microactuators integrated with morphological computation is presented.The microactuators combine conducting polymers to provide the actuation,with spatially designed structures for a morphologically controlled,user-defined actuation.Soft lithography is employed to pattern and fabricate polydimethylsiloxane layers with geometrical pattern,for use as a construction element in the microactuators.These microactuators could obtain multiple bending motions from a single fabrication process depending on the morphological pattern defined in the final step.Instead of fabricating via conventional photolithography route,which involves multiple steps with different chromium photomasks,this new method uses only one single design template to produce geometrically patterned layers,which are then specifically cut to obtain multiple device designs.The desired design of the actuator is decided in the final step of fabrication.The resulting microactuators generate motions such as a spiral,screw,and tube,using a single design template.
基金the Austrian Science Fund(FWF)within project P-27297(CaviCool)and W1210-N25(COQUS),and I 3167-N27(SiC-EiC)the WWTF within the project ICT12-041(PhoCluDi)+1 种基金the TU Innovative Projekte for financial supportfinancial support from the Erwin Schrodinger Center for Quantum Science&Technology(ESQ)of the Austrian Academy of Sciences in the project ROTOQUOP.
文摘Optical resonators are essential for fundamental science,applications in sensing and metrology,particle cooling,and quantum information processing.Cavities can significantly enhance interactions between light and matter.For many applications they perform this task best if the mode confinement is tight and the photon lifetime is long.Free access to the mode center is important in the design to admit atoms,molecules,nanoparticles,or solids into the light field.Here,we demonstrate how to machine microcavity arrays of extremely high quality in pristine silicon.Etched to an almost perfect parabolic shape with a surface roughness on the level of 2A and coated to a finesse exceeding F=500,000,these new devices can have lengths below 17μm,confining the photons to 5μm waists in a mode volume of 88λ^(3).Extending the cavity length to 150μm,on the order of the radius of curvature,in a symmetric mirror configuration yields a waist smaller than 7μm,with photon lifetimes exceeding 64 ns.Parallelized cleanroom fabrication delivers an entire microcavity array in a single process.Photolithographic precision furthermore yields alignment structures that result in mechanically robust,pre-aligned,symmetric microcavity arrays,representing a lightmatter interface with unprecedented performance.
基金Horizon 2020 Framework Programme (780240,828893)Austrian Science Fund (M2485-N34)MEYS CR(LM2018110)。
文摘Long-wave infrared(LWIR, 8–14 μm) photonics is a rapidly growing research field within the mid-IR with applications in molecular spectroscopy and optical free-space communication. LWIR applications are often addressed using rather bulky tabletop-sized free-space optical systems, preventing advanced photonic applications,such as rapid-time-scale experiments. Here, device miniaturization into photonic integrated circuits(PICs) with maintained optical capabilities is key to revolutionize mid-IR photonics. Subwavelength mode confinement in plasmonic structures enabled such miniaturization approaches in the visible-to-near-IR spectral range. However,adopting plasmonics for the LWIR needs suitable low-loss and-dispersion materials with compatible integration strategies to existing mid-IR technology. In this paper, we further unlock the field of LWIR/mid-IR PICs by combining photolithographic patterning of organic polymers with dielectric-loaded surface plasmon polariton(DLSPP) waveguides. In particular, polyethylene shows favorable optical properties, including low refractive index and broad transparency between ~2 μm and 200 μm. We investigate the whole value chain, including design, fabrication, and characterization of polyethylene-based DLSPP waveguides and demonstrate their first-time plasmonic operation and mode guiding capabilities along S-bend structures. Low bending losses of ~1.3 d B and straight-section propagation lengths of ~1 mm, pave the way for unprecedented complex on-chip mid-IR photonic devices. Moreover, DLSPPs allow full control of the mode parameters(propagation length and guiding capabilities) for precisely addressing advanced sensing and telecommunication applications with chip-scale devices.
