Improved surface quality of anisotropically etched silicon {111} planes for mm-scale integrated optics

We have studied the surface quality of millimeter-scale optical mirrors produced by etching CZ and FZ silicon wafers in potassium hydroxide to expose the $\{111\}$ planes. We find that the FZ surfaces have four times lower noise power at spatial frequencies up to $500\, {mm}^{-1}$. We conclude that mirrors made using FZ wafers have higher optical quality

Room temperature phase transition of W‐doped VO₂ by atomic layer deposition on 200 mm Si wafers and flexible substrates

The unique structural transition of VO₂ between dielectric and metallic phases has significant potential in optical and electrical applications ranging from volatile switches and neuromorphic computing to smart devices for thermochromic control and radiative cooling. Critical condition for their widespread implementation is scalable deposition method and reduction of the phase transition to near room temperature. Here, a W:VO₂ process based on atomic layer deposition (ALD) is presented that enables precise control of W-doping at the few percent level, resulting in a viable controllable process with sufficient W incorporation into VO₂ to reduce the phase transition to room temperature. It is demonstrated that the incorporation of 1.63 at.% W through ALD growth leads to a state-of-the-art phase transition at 32 °C with emissivity contrast between the low-temperature and high-temperature phase exceeding 40% in a metasurface-based radiative cooling device configuration. The process is shown to be viable on 200 mm silicon substrates as well as flexible polyimide films. The full and self-consistent temperature-dependent characterization of the W-doped VO2 using spectroscopic ellipsometry, electrical conductivity, mid-wave infrared camera, and Fourier transform infrared emissivity, allows for a fully validated material model for the theoretical design of various smart and switchable device applications

Single stage deflection amplification in a SOG capacitive acceleromoter

peer reviewe

Deflection amplification mechanism in a capacitive accelerometer

peer reviewe

Low noise vacuum MEMS closed-loop accelerometer using sixth-order multi-feedback loops and local resonator sigma-delta modulator

This paper reports on the design, implementation of a novel sixth-order sigma-delta modulator (ΣΔM) MEMS closed-loop accelerometer with extended bandwidth in a vacuum environment (~0.5Torr), which can coexist on a single die (or package) with other sensors requiring vacuum packaging. The fully differential accelerometer sensing element with a large proof mass (4×7mm2) was designed and fabricated on a Silicon-on-Insulator (SOI) wafer with 50μm-thick structural layer. Four electronic integrators were cascaded with the sensing element for high-order noise shaping ability. The local feedback paths created a local resonator producing a notch to further suppress the total in-band quantization noise. Measurement results show the overall noise floor achieved was -120dBg/√Hz, which is equivalent to a noise acceleration value of 1.2μg/√Hz in a 500Hz bandwidth; the scale factor was 950mV/g for input accelerations up to ±6g