This study proposes a new-fashioned plasmonic photoconductive antenna (PCA) with high optical-to-terahertz (THz) conversion efficiency. Finite element method was used to investigate and optimize the interaction of 800 nm femtosecond laser with the designed nanodisk array in the antenna's gap using its geometrical parameters. According to the simulation results, our optimized nanoplasmonic structure showed more than 38% enhancement in the absorption efficiency compared to the conventional structure without any nanostructure. Measuring the THz radiation of the fabricated PCAs using a time domain spectroscopy setup exhibited an exceptional 5.6 times higher electric field in 0.1–2.5 THz range compared to a similar PCA but without nanoplasmonic structure.

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We present a technique to fabricate ultrathin (down to 20 nm) uniform electron transparent windows at dedicated locations in a SiN membrane for in situ transmission electron microscopy experiments. An electron-beam (e-beam) resist is spray-coated on the backside of the membrane in a KOH-etched cavity in silicon which is patterned using through-membrane electron-beam lithography. This is a controlled way to make transparent windows in membranes, whilst the topside of the membrane remains undamaged and retains its flatness. Our approach was optimized for MEMS-based heating chips but can be applied to any chip design. We show two different applications of this technique for (1) fabrication of a nanogap electrode by means of electromigration in thin free-standing metal films and (2) making low-noise graphene nanopore devices.

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In this paper, a novel method for fabrication of an ionic polymer-metal composite (IPMC)-based humidity sensor is developed and optimized. IPMC is a kind of smart material that can work as a sensor or an actuator in wet environments or liquids. Poor adhesion between electrodes and the polymer and peeling off phenomenon are common problems in IPMC fabrication. Mechanical roughening, plasma treatment of the polymer surface and sputtering a thin layer of Ti and Cr as adhesion layers between polymer and Au electrodes are proposed to solve these issues. Different fabricated IPMC electrodes were then used as a capacitor to measure the relative humidity variations at different deflections and relative humidity conditions and the results have been compared. Our results show that IPMC using Au with 990 nm thicknesses worked properly and a sensitivity value of 13.43% was achieved.@en

Today, finding a low cost, efficient, functional and reliable solution for controlling smart lighting systems has become topic of many research groups and industry. In this study, a multi-functional wafer level package (WLP) for phosphor-based white LED system has been designed and manufactured using 7-mask BiCMOS process. This package integrates 4 high power blue LED dies with a temperature sensor and a blue selective light sensor for monitoring system performance. Each sensor has been designed, characterized and calibrated to be part of the smart monitoring unit. An interdigitated power transistor and a 4-bit flash analog-to-digital converter (ADC) were also monolithically integrated with sensors’ readout and extra controlling functions.

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Given the performance decay of high-power light-emitting diode (LED) chips over time and package condition changes, having a reliable output light for sensitive applications is a point of concern. In this study, a light feedback control circuit, including blue-selective photodiodes, for blue/ultraviolet (UV) LED, has been designed and implemented using a low-cost seven-mask BiCMOS process. The feedback circuit was monolithically integrated in a package with four high-power blue LED chips. For sensing the intensity of exact colored blue/UV light in the package, selective photodiodes at 480-nm wavelength were implemented. An opamp-based feedback circuit combined with a high-power transistor controls the output light based on real-time sensor data. The whole system is a low-cost integrated package that guarantees a stable and reliable output light under different working conditions. Output light can be also controlled linearly by a reference input voltage.

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This study presents a blue light detector for evaluating the output light of phosphor based white LED package. It is composed of a silicon stripe-shaped photodiode designed and implemented in a 2 μm BiCMOS process which can be used for wafer level integration of different passive and active devices all in just 5 lithography steps. The final device shows a high selectivity to blue light. The maximum responsivity at 480nm is matched with the target blue LED illumination. The designed structure have better responsivity compared to simple photodiode structure due to reducing the effect of dead layer formation close to the surface because of implantation. It has also a two-fold increase in the responsivity and quantum efficiency compared to previously similar published sensors.@en