We measure the stiction force using in-plane electrostatically actuated Si nanoelectromechanical cantilever relays with Pt contacts. The average, current-dependent values of stiction force ranging from 60 nN to 265 nN were extracted using the IDS vs VGS hysteresis curves, the cantilever displacement information from finite element method (Comsol Multiphysics)simulations, and force distribution determined using an analytical model. It is shown that stiction force is inversely and directly proportional to the contact resistance (Rc) and drain-source current (IDS), respectively. Using the dependence of stiction force on contact current, we demonstrate the tuning of voltage hysteresis for a same relay from 8V to 36V (equivalent to a stiction force of 70 nN to 260 nN respectively). We attribute the stiction force primarily to the metallic bonding force which shows a strong dependence on the contact current.

Nanoporous (np)-TiO 2 films have multiple applications, including dye-sensitized and perovskite solar cells. However, preparation of np-TiO 2 films on transparent conductive oxide-coated surfaces (e.g., fluorine doped tin oxide (FTO)) requires high-temperature sintering (450−500 °C) for at least 30−60 min in a conventional oven. Here, we introduce a novel technique to rapidly produce np-TiO 2 films on FTO-coated glass substrates via microwave (MW) irradiation. np-TiO 2 films were sintered on FTO-glass substrates in less than 10 min at temperatures less than 260 °C using an optimized MW irradiation program and a simple MW attenuation technique. Significantly, cracking of FTO-coated glass substrates was avoided during MW irradiation, which was a limiting problem in previous studies. MW-developed films were evaluated with UV−vis absorption spectrophotometry, Raman spectroscopy, X-ray diffraction, and atomic force microscopy, with MW-developed films (>4 min) producing essentially identical characteristics as conventionally annealed films. Dye-sensitized solar cells (DSSCs) fabricated with MW-developed films (8 min) demonstrated an overall power conversion efficiency of 7.16% as compared to 7.04% for conventionally-fabricated DSSCs. This rapid and low-temperature sintering technique saves time and energy and may also pave the way for deposition of np-TiO 2 films on plastic-based substrates.

The effects of miniaturization on theoretically predicted performance of dual-period guided mode resonance (GMR) transmission filters, which demonstrate immense potential for multispectral imaging in short wave infrared (SWIR), have been compared with experimental findings. With reducing filter size from 112 periods (90 µm) to 12 periods (10 µm), peak transmittance (Tpeak) of simulated and measured filters reduced gradually from 84% to 55% and from 76% to 65%, respectively, with a moderate change of 1 - 3 nm in full width at half maximum (FWHM). For 6 period filters (5 µm), simulations predict drastically reduced Tpeak = 14% accompanied by increase in FWHM by 12 nm. The Tpeak value is theoretically shown to increase to 46% with FWHM reduced by 7 nm upon placing metal reflectors at the optimum positions to increase the optical path length. Our findings indicate that four 5 µm × 5 µm size filters with metal reflectors designed for different resonance wavelengths can be used to form a single, 20 µm × 20 µm mosaic pixel for SWIR multispectral imaging.

Typical guided-mode resonance (GMR) transmission filter design, which is based on a single ridge per period, necessitates multiple etching/fabrication steps for implementing an array of filters (having different transmission bands) on the same substrate. To address this problem, we demonstrate dual-period narrow bandpass GMR filters that offer more degrees of freedom, two periods and two fill-factors, for tuning the filter characteristics and achieving wider stop bands without changing the grating height. A set of six transmission filters with well-separated passbands in the short-wave infrared region was designed using COMSOL Multiphysics simulations and produced on the same silicon-on-quartz wafer in a single fabrication run. The 90 µ m × 90 µ m size filters exhibited passbands as narrow as 15 nm with peak-wavelength tunability over 200 nm, flat stop bands as wide as ∼ 400 n m , and peak transmittance reaching 87%. The experimental transmission spectra were in good agreement with the corresponding simulations. These findings pave the way for the realization of pixel size filter arrays for multispectral image sensors.

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