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Based on the principle of the Villari effect, a force sensor with a giant magnetostrictive material (GMM) as the sensitive element, high linearity, and a large range was studied. A Hall element integrated into the structure was used to detect the magnetic flux density and measure the external force. First, the finite element method was used to verify the validity of the intended magnetization process. Second, an equation for GMM magnetization was derived based on the Jiles–Atherton (J–A) model and the magneto-mechanical coupling effect. The relationships between magnetization and the biased magnetic field, and magnetization and the external force were analyzed under the dynamic coupling model of positive and negative effects. Finally, the influences of various biased magnetic fields and external forces on the sensor output characteristics were determined experimentally. The sensitivity of the designed force sensor was 0.337 mV/N when the bias current was 1.2 A and the preload was 120 N. When a force of 1000 N was applied, the linearity was 0.82%. The experimental results are consistent with the theoretical design values. These research results aid in the development of a highly linear, large-range force sensor. This study provides the theoretical and technical foundations for a high-performance force sensor that can be used in industrial testing.

Three-dimensional (3D) integration technology using Cu interconnections has emerged as a promising solution to improve the performance of silicon microelectronic devices. However, Cu diffuses into SiO2 and requires a barrier layer such as Ta to ensure acceptable reliability. In this paper, the effects of temperature and strain normal to the interface on the inter-diffusion of Cu and Ta at annealing conditions are investigated using a molecular dynamics (MD) technique with embedded atomic method (EAM) potentials. Under thermal annealing conditions without strain, it is found that a Cu-rich diffusion region approximately 2 nm thick is formed at 1000 K after 10 ns of annealing. Ta is capable of diffusing into the interior of Cu but Cu hardly diffuses into the inner lattice of Ta. At the Cu side near the interface an amorphous structure is formed due to the process of diffusion. The diffusion activation energy of Cu and Ta are found to be 0.9769 and 0.586 eV, respectively. However, when a strain is applied, a large number of crystal defects are generated in the sample. As the strain is increased, extrinsic stacking faults (ESFs) and lots of Shockley partial dislocations appear. The density of the dislocations and the diffusion channels increase, promoting the diffusion of Cu atoms into the inner lattice of Ta. The thickness of the diffusion layer increases to 4 times the value when only a temperature load of 700 K is applied. The MD simulations demonstrated that Ta is very effective as a barrier layer under thermal loading only, and its effectiveness is impaired by tensile strain at the Cu/Ta interface. The simulations also clarified the mechanism that caused the impairment. The methodology and approach described in this paper can be followed further to study the effectiveness of barrier layers under various annealing and strain conditions, and to determine the minimum thickness of barrier layers required for a particular application.

We theoretically investigated third harmonic generation (THG) from planar chiral metamaterials consisting of a square array of gammadion-shaped metal-insulator-metal multilayered nanostructures. We show that there exists strong circular dichroism (CD) for THG on the proposed chiral metamaterials. We also demonstrate that geometrically mirroring the gammadion -shaped meta-atoms can result in reversal of the THG-CD effect. Based on these CD effects in the optical nonlinear regime, we propose a design of a Fresnel zone plate (FZP) for intense focusing of the THG signals, in which adjacent zones of the FZP consist of gammadions with mirror symmetry and generate circularly polarized THG with opposite handedness. Furthermore, we demonstrate that the relative phase of the THG can be continuously changed by rotating the gammadion around its rotational axis, which could be used in the FZP to control the polarization of the output THG signals.

We report experimental investigation of the photoluminescence (PL) generated from the gold nanoshells of the dielectric-metal core-shell resonators (DMCSR) that support multipolar electric and magnetic based cavity plasmon resonances. Significantly enhanced and modulated PL spectrum is observed. By comparing the experimental results with analytical Mie calculations, we are able to demonstrate that the observed reshaping effects are due to the excitations of those narrow-band cavity plasmon resonances. We also present that the variation on the dielectric core size allows for tuning the cavity plasmon resonance wavelengths and thus the peak positions of the PL spectrum.

Solution-processed graphene quantum dots (GQDs) possess a moderate bandgap, which make them a promising candidate for optoelectronics devices. However, negative photoconductivity (NPC) and hysteresis that happen in the photoelectric conversion process could be harmful to performance of the GQDs-based devices. So far, their origins and relations have remained elusive. Here, we investigate experimentally the origins of the NPC and hysteresis in GQDs. By comparing the hysteresis and photoconductance of GQDs under different relative humidity conditions, we are able to demonstrate that NPC and hysteresis coexist in GQDs and both are attributed to the carrier trapping effect of surface adsorbed moisture. We also demonstrate that GQDs could exhibit positive photoconductivity with three-order-of-magnitude reduction of hysteresis after a drying process and a subsequent encapsulation. Considering the pervasive moisture adsorption, our results may pave the way for a commercialization of semiconducting graphene-based and diverse solution-based optoelectronic devices.

We analyze the U-shaped metallic split-ring resonators (SRRs) aimed at creating highly confined and enhanced magnetic field in the near-infrared frequency range. At the magnetic resonance, the induced circulating current of the SRRs could lead to a strong enhancement of the surrounding magnetic field. Such a magnetic field enhancement is found to be dominated by the gap width between two SRR arms. By decreasing the gap width to 10 nm, the SRR is predicted to have a 3790-fold enhancement of the magnetic field at the resonance wavelength of 1340 nm.

Based on the contra-directional coupling, a composite structure consisting of two coupled metal-insulator-metal (MIM) waveguides is proposed to act as an attractive plasmonic reflector. By introducing a defect into one of the MIM waveguides, we show that such a composite structure can be operated as a plasmonic nanocavity with a high quality factor. Both symmetric and anti-symmetric cavity modes are supported in the plasmonic cavity, and their resonance frequencies can be tuned by controlling the defect width. The present structures could have a significant impact for potential applications such as surface plasmon mirrors, filters and solid-state cavity quantum electrodynamics.

We report experimentally that for a particular high-symmetry planar periodic arrangement of metal double-triangle nanoparticle arrays fabricated via angle resolved nanosphere lithography, both anti-symmetric and symmetric magnetic resonances can be explicitly excited at off-normal incidence. Further, we demonstrate that the underlying mechanism for the formation of these two modes is a result of direct interactions with the incident electric and magnetic fields, respectively. As a consequence, with increasing the incident angle there is a relatively small blue-shift in the transmission for the electric-field induced anti-symmetric mode, while a remarkable red-shift is observed for the magnetic-field induced symmetric mode.

The thermal stress due to the thermal expansion mismatch could induce crystallographic defects such as buckling and cracking and degrade device performance. In this paper, the thermal stress distribution in a laser array structure selectively grown on V-groove-patterned Si substrates was investigated by two-dimension finite-element method. Surprisingly, unexpected results are observed that the top of the InGaAs active layer and the most region of the InP cap layer are in compression, which is far different from the thermal stress distribution in planar structures. Two mechanisms have been proposed and modeled to explain the difference—(i) the width of uncoalesced layers is smaller than that of the Si substrate, which causes thermal stress to change in epitaxial layers, and (ii) thermal stress in the InGaAs and InP layers is affected by the V-groove structure. The results show that whether or not the epitaxial layers are coalesced has significant effect on the thermal stress distribution. The effect of the height of the V-groove, the height and the width of the SiO2 mask on the thermal stress distribution was also studied. It is found that the height of V-groove and the height of SiO2 mask play a critical role in the stress distribution. These findings are useful for the optimal designs for the laser array and provide an important step towards the realization of photonic integration circuits on silicon.