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The investigation of hydrostatic pressure dependent optoelectronic properties of GaAsNBi spherical quantum dot
摘要： The electronic band structure of GaAsNBi spherical quantum dot (QDs) have been calculated under hydrostatically induced pressure using 16 band k.p model and considering the band anticrossing (BAC) interaction between the valence band (VB) of the host material with the N and Bi related resonant impurity level. It has a linear variation in bandgap with different Bi concentration and non-linear in bandgap with varying pressure, for 2.3%N in both the cases. However, small differences are observed in valance band offset (VBO), whereas more considerable changes can be seen in the conduction band offset (CBO) with an increasing hydrostatic pressure, which implies a stronger confinement of charge carriers. Finally, we also studied the percentage of strain distribution and its related properties of GaAsNBi spherical QDs along the radial direction, lattice misfit under biaxial and hydrostatic strain. These QDs are also being used in many applications, including selective frequency operation for optoelectronic devices by tuning distinct mole fraction and pressure.
关键词： Strain,Optical gain,Band offset,k.p method
更新于2025-09-16 10:30:52
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Highly Sensitive and Reliable Strain Sensor Based on MoS <sub/>2</sub> -Decorated Laser-Scribed Graphene for Wearable Electronics
摘要： We propose a strategy for the fabrication of a highly sensitive and reliable strain sensor based on MoS2-decorated laser-scribed graphene (MDS-LSG) for flexible and wearable electronics. The laser-thinning of multilayered MoS2 coated on commercial polyimide (PI) film using a CO2 infrared laser exhibits three-dimensional hierarchical porous graphene network decorated with MoS2 enabling superior electrical properties. By exploiting the advantage of high mobility of graphene and strain-dependent property of MoS2, the technique offers a rapid route towards a simple, facile and scalable approach for the fabrication of high-performance strain sensor. As fabricated sensor endows high sensitivity (gauge factor, GF ~290), wide working range, fast response time and stability over 7000 cycles. Finally, we successfully apply the sensor’s performance for subtle deformation of the skin (wrist pulse) and various human-motion detections.
关键词： subtle strain,laser scribing,MoS2-decorated laser-scribed graphene (MDS-LSG),strain sensor
更新于2025-09-12 10:27:22
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Morphologically modulated laser-patterned reduced graphene oxide strain sensors for human fatigue recognition
摘要： Laser heating provides an effective method to produce thermally reduced graphene oxide (rGO), it can also pattern the designed layout on the surface of graphene oxide (GO) during the reduction process. In this work, we demonstrated a flexible strain sensor based on the morphologically modulated laser-patterned reduced graphene oxide (LPG) film with a one-step process. Compared with the strain sensor using flat patterned rGO (0-1.2%) and curved-grid patterned rGO (CGPG) (0-4.1%), the strain sensor based on rectangular-grid patterned rGO (RGPG) have highest gauge factor (GF), up to 133 under 2.7% of physical deformation. Meanwhile, the RGPG strain sensors exhibit extraordinary linearity in a relatively large range of deformation (0-2.7%) and excellent endurance for over 1000 stretching-releasing circles. The RGPG strain sensor was used to monitor human fatigue. By analyzing eye blinking frequency and duration, it is possible to evaluate the fatigue level. We anticipate that the RGPG based strain sensor, prepared via a relatively simple and cost-effective process, may open up a broad spectrum of practical applications, such as driver fatigue evaluation and smart monitoring of human body movements.
关键词： wearable electronics,laser patterning,fatigue evaluation,flexible strain sensor,reduced graphene oxide
更新于2025-09-12 10:27:22
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Mechanism of improved luminescence intensity of Ultraviolet Light Emitting Diodes (UV-LEDs) under thermal and chemical treatments
摘要： In this work, the influences of thermal annealing and chemical passivation on the optical and electrical properties of ultraviolet light-emitting-diode (UV-LED) were investigated. The electroluminescence (EL) intensities of the LEDs under KOH treatment and thermal annealing increased by 48% and 81%, respectively compared to as-fabricated LED under current level of 10 mA. Cathodoluminescence (CL) mapping of UV-LEDs confirmed no variation of the density of the non-radiative recombination centers after surface treatments, and no obvious change in surface morphology was identified due to lacking of energy for surface atom migration. However, Raman spectroscopy indicates a relaxation of compressive strains inside the thin film after both thermal and chemical treatments, and conductive atomic force microscopy (c-AFM) also illustrated reduced leakage current after KOH passivation, which are responsible for the improved luminescence properties of UV-LEDs.
关键词： surface treatment,UV-LED,electroluminescence,strain relaxation
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - Seoul, Korea (South) (2019.1.27-2019.1.31)] 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - Development of a Highly Stretchable Strain Sensor Based on Patterned and Rolled Carbon Nanotubes
摘要： This paper reports a highly stretchable strain sensor consisting of patterned and rolled carbon nanotubes (CNTs) embedded in an elastomer. To form overlapped lines of CNTs on the elastomer, vertically aligned CNTs (VACNTs) are grown on the patterned catalytic sites and rolled out by a roller. In the initial unloaded state, these lines of CNTs are overlapped with each other. Under loading, the flexible substrate is extended, and the overlapped CNT lines are slid and separated, increasing the electrical resistance. The fabricated sensor showed excellent sensing performances including broad sensing range (>500% strain), high sensitivity (gauge factor >28), high repeatability, and durability. In addition, since the shape of the CNT lines determines the resistance through the deformed lines of CNTs under applied strain, the performance of the sensor can be further improved by optimizing the pattern design. Therefore, the sensor would be an attractive candidate for diverse applications of strain sensors.
关键词： high sensitivity,elastomer,stretchable strain sensor,carbon nanotubes,broad sensing range
更新于2025-09-12 10:27:22
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Interfacial Lattice‐Strain‐Driven Generation of Oxygen Vacancies in an Aerobic‐Annealed TiO <sub/>2</sub> (B) Electrode
摘要： Oxygen vacancies play crucial roles in defining physical and chemical properties of materials to enhance the performances in electronics, solar cells, catalysis, sensors, and energy conversion and storage. Conventional approaches to incorporate oxygen defects mainly rely on reducing the oxygen partial pressure for the removal of product to change the equilibrium position. However, directly affecting reactants to shift the reaction toward generating oxygen vacancies is lacking and to fill this blank in synthetic methodology is very challenging. Here, a strategy is demonstrated to create oxygen vacancies through making the reaction energetically more favorable via applying interfacial strain on reactants by coating, using TiO2(B) as a model system. Geometrical phase analysis and density functional theory simulations verify that the formation energy of oxygen vacancies is largely decreased under external strain. Benefiting from these, the obtained oxygen-deficient TiO2(B) exhibits impressively high level of capacitive charge storage, e.g., ≈53% at 0.5 mV s?1, far surpassing the ≈31% of the unmodified counterpart. Meanwhile, the modified electrode shows significantly enhanced rate capability delivering a capacity of 112 mAh g?1 at 20 C (≈6.7 A g?1), ≈30% higher than air-annealed TiO2 and comparable to vacuum-calcined TiO2. This work heralds a new paradigm of mechanical manipulation of materials through interfacial control for rational defect engineering.
关键词： aerobic-annealing,oxygen vacancy,pseudocapacitive charge storage,lithium-ion batteries,interfacial lattice strain
更新于2025-09-12 10:27:22
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Anomalous Stranski-Krastanov growth of (111)-oriented quantum dots with tunable wetting layer thickness
摘要： Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In0.52Al0.48As(111)A surfaces lattice-matched to InP substrates. In this study, we show that the tensile-strained self-assembly process for these GaAs(111)A QDs unexpectedly deviates from the well-known Stranski-Krastanov (SK) growth mode. Traditionally, QDs formed via the SK growth mode form on top of a flat wetting layer (WL) whose thickness is fixed. The inability to tune WL thickness has inhibited researchers’ attempts to fully control QD-WL interactions in these hybrid 0D-2D quantum systems. In contrast, using microscopy, spectroscopy, and computational modeling, we demonstrate that for GaAs(111)A QDs, we can continually increase WL thickness with increasing GaAs deposition, even after the tensile-strained QDs (TSQDs) have begun to form. This anomalous SK behavior enables simultaneous tuning of both TSQD size and WL thickness. No such departure from the canonical SK growth regime has been reported previously. As such, we can now modify QD-WL interactions, with future benefits that include more precise control of TSQD band structure for infrared optoelectronics and quantum optics applications.
关键词： wetting layer,quantum dots,tensile strain,Stranski-Krastanov growth,optoelectronics
更新于2025-09-12 10:27:22
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Broad tunability of emission wavelength by strain coupled InAs/GaAs <sub/>1???x</sub> Sb <sub/>x</sub> quantum dot heterostructures
摘要： Tuning of the photoluminescence emission over a wider range of optical telecommunication wavelength (1.38 μm–1.68 μm) has been achieved by employing a GaAs1 ? xSbx capping layer to the strain coupled bilayer InAs quantum dot (QD) heterostructures. It is shown that the modulation of strain between the two dot layers through variation in Sb-content and thickness of the capping layer strongly influence the dot size. The band alignment transformation from type-I to type-II is observed for high Sb-content in the capping layers. In addition, the carrier lifetime is improved by a factor of three in the QD heterostructures having type-II band alignment. This, we believe, is of importance for optoelectronic device applications.
关键词： GaAs1 ? xSbx capping layer,carrier lifetime,optoelectronic device applications,photoluminescence emission,strain coupled bilayer InAs quantum dot,type-I to type-II band alignment,optical telecommunication wavelength
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - GeSn Lasers with Uniaxial Tensile Strain in the Gain Medium
摘要： We use strain redistribution to locally enhance strain in GeSn layers. We demonstrate uniaxial tensile strain in microbridges with lasing cavities tuned over the 3.1 to 4.6μm range, and thresholds lower than 10 kW.cm-2 at 25K, in pulsed excitation mode. Laser operation vanishes around 273K.
关键词： laser,tunability,strain,GeSn
更新于2025-09-12 10:27:22
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Size-dependent instability of organic solar cell resting on Winkler-Pasternak elastic foundation based on the modified strain gradient theory
摘要： The present study employs the modified strain gradient theory (MSGT) in conjunction with the refined shear deformation plate theory to explore the buckling behaviour of simply supported and clamped OSC. The Winkler-Pasternak elastic foundation is implemented to idealise the foundation. The size-dependent effect of the OSC is captured by the three length scale parameters within the MSGT. The Hamilton principle is used to derive the equations of motion and the boundary conditions, and the Galerkin procedure is subsequently implemented to obtain the critical buckling load. Subsequently, the framework is extended to the thermally induced buckling behaviour, and three types of temperature rise patterns, namely uniform, linear and nonlinear temperature variations, along the thickness of the OSC are considered. Several verification studies are conducted to illustrate the accuracy of the present method. Besides, size-dependent material properties are taken into consideration during the numerical experiments. Thorough studies are conducted to demonstrate the difference between critical buckling loads and temperature variations obtained from the MSGT, the modified couple stress theory (MCST), and the classical plate theory (CPT) models. Furthermore, the effects of length scale parameter (hl), the aspect ratio (ab), the length-to-thickness ratio (ah) and the Winkler-Pasternak elastic foundation parameters on the buckling behaviour of the OSC are also revealed by the numerical results.
关键词： Refined shear deformation plate theory,Strain gradient elasticity theory,Thermal buckling,Organic solar cell,Mechanical buckling,Elastic foundation
更新于2025-09-12 10:27:22