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Invited Article: Scalable high-sensitivity optomechanical magnetometers on a chip
摘要： The dual-resonant enhancement of mechanical and optical response in cavity optomechanical magnetometers enables precision sensing of magnetic fields. In previous working prototypes of such magnetometers, a cavity optomechanical system is functionalized by manually epoxy-bonding a grain of magnetostrictive material. While this approach allows proof-of-principle demonstrations, practical applications require more scalable and reproducible fabrication pathways. In this work, we developed a multiple-step method to scalably fabricate optomechanical magnetometers on a silicon chip, with reproducible performance across different devices. The key step is to develop a process to sputter coat a magnetostrictive film onto high quality toroidal microresonators, without degradation of the optical quality factor. A peak sensitivity of 585 pT/√Hz is achieved, which is comparable with previously reported results using epoxy-bonding. Furthermore, we demonstrate that thermally annealing the sputtered film can improve the magnetometer sensitivity by a factor of 6.3.
关键词： optomechanical magnetometers,thermal annealing,sensitivity enhancement,sputter coating,scalable fabrication
更新于2025-09-23 15:19:57
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Electronic surface, optical and electrical properties of p – GaN activated via in-situ MOCVD and ex-situ thermal annealing in InGaN/GaN LED
摘要： Electronic surface properties, optical and electrical characteristics of p-type Mg-doped Gallium Nitride (p-GaN) activated under different thermal annealing condition were investigated. In this work, p-GaN samples were subjected to in-situ and ex-situ thermal annealing process at 650°C in Nitrogen (N2) rich condition. In-situ annealing process took place in Metal Oxide Chemical Vapor Deposition (MOCVD) chamber while ex-situ annealing process was carried out in the conventional oven. X-Ray and Ultraviolet Photoemission Spectroscopy (XPS/UPS) were used to observe the energy alignment of the p-GaN surface. From PES spectra, the sample subjected to in-situ thermal annealing shown to exhibit lower surface bend bending of 0.28 eV as compared to ex-situ thermal annealing activation with 0.45 eV band bending. This result is in agreement with specific contact resistance measurement that shows in-situ sample exhibits lower resistance resulted in better carrier injection from metal to p-GaN. Photoluminescence (PL) spectra elucidates that in-situ sample has a good surface quality with less nitrogen related vacancies (VN) formed on the p-GaN surface. All these results are further proved with the higher output power from LED with in-situ annealing. At 20 mA, in-situ sample shown an increment of ~14% light output power compared to ex-situ sample. Results obtained in this work suggest that the thermal activation condition for p-GaN activation process plays an active role on the surface quality as well as the energy alignment of the film surface and shows the potential of in-situ p-GaN activation for tunnel junction structure.
关键词： ex-situ,p-GaN,in-situ,thermal annealing,LED
更新于2025-09-19 17:13:59
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π–π Stacking Distance and Phase Separation Controlled Efficiency in Stable All-Polymer Solar Cells
摘要： The morphology of the active layer plays a crucial role in determining device performance and stability for organic solar cells. All-polymer solar cells (All-PSCs), showing robust and stable morphologies, have been proven to give better thermal stability than their fullerene counterparts. However, outstanding thermal stability is not always the case for polymer blends, and the limiting factors responsible for the poor thermal stability in some All-PSCs, and how to obtain higher efficiency without losing stability, still remain unclear. By studying the morphology of poly [2,3-bis (3-octyloxyphenyl) quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl](TQ1)/poly[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]] (PCE10)/PNDI-T10 blend systems, we found that the rearranged molecular packing structure and phase separation were mainly responsible for the poor thermal stability in devices containing PCE10. The TQ1/PNDI-T10 devices exhibited an improved PCE with a decreased π–π stacking distance after thermal annealing; PCE10/PNDI-T10 devices showed a better pristine PCE, however, thermal annealing induced the increased π–π stacking distance and thus inferior hole conductivity, leading to a decreased PCE. Thus, a maximum PCE could be achieved in a TQ1/PCE10/PNDI-T10 (1/1/1) ternary system after thermal annealing resulting from their favorable molecular interaction and the trade-off of molecular packing structure variations between TQ1 and PCE10. This indicates that a route to efficient and thermal stable All-PSCs can be achieved in a ternary blend by using material with excellent pristine efficiency, combined with another material showing improved efficiency under thermal annealing.
关键词： morphology,device stability,crystallinity,all-polymer solar cells,thermal annealing,molecular packing structure
更新于2025-09-19 17:13:59
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Effect of two-step post-treatment on optical properties, microstructure, and nanosecond laser damage threshold of HfO <sub/>2</sub> /TiO <sub/>2</sub> /SiO <sub/>2</sub> multilayer high reflection films
摘要： HfO2/TiO2/SiO2 periodic multilayer high reflection films deposited by an electron beam are post-treated by two-step post-treatment and thermal annealing post-treatment, respectively. The optical properties, microstructures, surface morphologies, and laser-induced damage threshold (LIDT) of the films are studied comparatively. The results show that the two-step post-treatment enhances the high reflection films’ density and reduces the film surface roughness and the defects of the film. The test results show that the LIDT of HfO2/TiO2/SiO2 high reflection films treated by two-step post-treatment reaches 32.8 J/cm2, which is 110.26% higher than that of the untreated film. Compared with the HfO2/TiO2/SiO2 high reflection films after thermal annealing post-treatment, the LIDT increased nearly 27.6% after two-step post-treatment. Two-step post-treatment of high reflection films can effectively remove the defects on the surface of the film, reduce the oxygen vacancies inside the film, and further increase the laser damage threshold of the high reflection films.
关键词： laser-induced damage threshold,HfO2/TiO2/SiO2,two-step post-treatment,thermal annealing,multilayer high reflection films
更新于2025-09-19 17:13:59
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Evaluating the interfacial properties of wrinkled graphene fiber through single-fiber fragmentation tests
摘要： Graphene ?ber has attracted much attention due to its potential applications in supercapacitors, dye-sensitized solar cells, actuators, motors, stretchable circuits and functional composites, owing to its high electrical conductivity, tensile strength and good ?exibility. The high tensile strength of graphene ?ber renders it promising candidate as the reinforcement in the composites. The interface is the key element for the ?ber-reinforced composites; however, there is no study about the interfacial evaluation about the graphene ?ber reinforcement composites. Herein, in this study, we fabricate the high-strength graphene ?bers (up to 890.1 MPa) through the wet spinning and thermal annealing method, make the graphene ?ber-reinforced single-?ber composite, and develop a novel and facile fragmentation test to quantitatively evaluate the interfacial performance of graphene ?ber. Graphene ?ber has the interfacial shear stress (IFSS) of 60.6 MPa, exhibiting one of the highest IFSS among the carbon nanotube yarns and commercial carbon ?bers composites. The superior interfacial performance of graphene ?ber is attributed to the surface wrinkles and grooves, which establishes strong physical interlocking between graphene ?ber and resin, favoring for the stress transfer. This work will pave the way for the development of graphene ?ber-reinforced composites.
关键词： Wet spinning,Thermal annealing,Graphene ?ber,Composites,Interfacial properties,Fragmentation test
更新于2025-09-19 17:13:59
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Thermal-Annealing Effects on Energy Level Alignment at Organic Heterojunctions and Corresponding Voltage Losses in All-Polymer Solar Cells
摘要： Matched energy level alignment is a key requirement for efficient organic devices such as organic light-emitting diodes, photovoltaics, and field-effect transistors. The effect of thermal stress/annealing on energy level alignment and related properties of the devices are less discussed compared to the extensively explored effect on morphology and corresponding device performance. Here all polymer solar cells (all-PSCs) are employed to study thermal annealing effects on energy level alignment and the corresponding effect on the device properties of the all-PSCs. It is found that optimized energy level alignment can be achieved by thermal annealing. An interface dipole layer at the donor/acceptor interface is introduced by energy level realignment that assists charge generation by reducing geminate recombination so that the voltage loss is dramatically reduced, improving the performance of the all-PSCs.
关键词： Thermal Annealing,Voltage losses,Polymer solar cell,General design rule,Energy level alignment
更新于2025-09-19 17:13:59
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Annealed Polycrystalline TiO <sub/>2</sub> Interlayer of the n-Si/TiO <sub/>2</sub> /Ni Photoanode for Efficient Photoelectrochemical Water Splitting
摘要： High photovoltage generation from a photoelectrode is important for efficient solar-driven water splitting. Here, we report a thermal treatment process that greatly enhances photovoltage generation from an n-Si/TiO2/Ni photoanode. By selectively annealing the TiO2 interlayer, the photoanode generates a high photovoltage of 570 mV, which is very competitive as compared with photovoltages produced using other similar metal?insulator?semiconductor structures with earth-abundant metal catalysts. Different annealing conditions and junction layer thicknesses were systematically investigated. It is found that the optimal annealing temperature occurs between 500 and 600 °C. Within this temperature range, the deposited amorphous Ti is converted into polycrystalline anatase phase TiO2. The optimal annealing time scales linearly with TiO2 thickness and inversely with annealing temperature. The large photovoltage generation is attributed to the reduced defect states and improved junction barrier height by the annealed TiO2 interlayer. This study demonstrates that thermal annealing offers an attractive approach to modify the TiO2 interlayer material’s properties for photovoltage optimization.
关键词： photovoltage,photoanode,water splitting,thermal annealing,photoelectrochemistry,junction interlayer
更新于2025-09-19 17:13:59
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Interfacial Energetic Level Mapping and Nano-Ordering of Small Molecule/Fullerene Organic Solar Cells by Scanning Tunneling Microscopy and Spectroscopy
摘要： Using scanning tunneling microscopy (STM) and spectroscopy (STS) at the liquid/solid interface, morphology evolution process and energetic level alignment of very thin solid films (thickness: <700 pm), of the low molecular weight molecule DRCN5T and DRCN5T:[70]PCBM blend are analyzed after applying thermal annealing at different temperatures. These films exhibit a worm-like pattern without thermal annealing (amorphous shape); however, after applying thermal annealing at 120 °C, the small molecule film domains crystallize verified by X-ray diffraction: structural geometry becomes a well-defined organized array. By using STS, the energy band diagrams of the semiconductor bulk heterojunction (blended film) at the donor-acceptor interface are determined; morphology and energy characteristics can be correlated with the organic solar cells (OSC) performance. When combining thermal treatment and solvent vapor annealing processes as described in previous literature by using other techniques, OSC devices based on DRCN5T show a very acceptable power conversion efficiency of 9.0%.
关键词： solvent vapor annealing,DRCN5T,scanning tunneling spectroscopy,organic solar cells,scanning tunneling microscopy,thermal annealing
更新于2025-09-16 10:30:52
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Nearly Epitaxial Low-Resistive Co Germanide Formed by Atomic Layer Deposited Cobalt and Laser Thermal Annealing
摘要： With ALD-Co on n+-Ge (ND of 2×1019 cm-3) as the platform, annealing schemes including rapid thermal annealing (RTA) and laser thermal annealing (LTA) were employed to study its impact on the characteristics of CoGe2. CoGe2 formed by LTA shows no agglomeration and a low ρc of 1.3×10-8 Ω-cm2 which is reduced by 54 % as compared to the counterpart RTA. In addition, a uniform and atomically smooth CoGe2 with nearly epitaxial crystal structure is also achieved by LTA. Furthermore, LTA-formed CoGe2 does not require any barrier layer during formation which is in stark difference to other germanides and would greatly improve line resistance of the ever scaled contact trench. The promising results mainly stem from the low thermal budget with significant thermal gradient/shallow heat distribution of LTA that effectively limits excess surface Co diffusion and grooving effect, proving the high contact performance enabler beyond 5 nm node.
关键词： smooth interface,cobalt germanide,laser thermal annealing,contact resistivity,barrier,epitaxial crystal structure
更新于2025-09-16 10:30:52
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<i>In situ</i> synthesis of monolayer graphene on silicon for near-infrared photodetectors
摘要： Direct integration of monolayer graphene on a silicon (Si) substrate is realized by a simple thermal annealing process, involving a top copper (Cu) layer as the catalyst and an inserted polymethylmethacrylate (PMMA) as the carbon source. After spin-coating the PMMA carbon source on the Si substrate, the Cu catalyst was deposited on PMMA/Si by electron beam evaporation. After that, graphene was directly synthesized on Si by decomposition and dehydrogenation of PMMA and the catalyzation effect of Cu under a simple thermal annealing process. Furthermore, under an optimized growth condition, monolayer graphene directly formed on the Si substrate was demonstrated. Utilizing the as-grown graphene/Si heterojunction, near-infrared photodetectors with high detectivity ((cid:1)1.1 (cid:3) 1010 cm Hz1/2 W(cid:4)1) and high responsivity (50 mA W(cid:4)1) at 1550 nm were directly fabricated without any post-transfer process. The proposed approach for directly growing graphene on silicon is highly scalable and compatible with present nano/micro-fabrication systems, thus promoting the application of graphene in microelectronic fields.
关键词： thermal annealing,PMMA,silicon,photodetectors,copper catalyst,graphene
更新于2025-09-16 10:30:52