Weibing Wang

CMOS MEMS infrared source based on black silicon

In this work, a MEMS infrared source applied to compact Non-Dispersive Infrared (NDIR) gas sensor is reported. Compared to other related things, the source coats integrated nanostructure black silicon compatible with CMOS technique on the poly-silicon. Hence the emissivity is as high as 98% at 3~5μm wave range; relatively the radiation efficiency is increased by 40% through calculation. Suspension structure and DRIE release process of the back side are used in the design to reduce the heat conduction losses, and the source is only sized 3×3mm2 suitable for mass production. After being packed, the source can rapidly heat in 20 ms, besides the modulation depth can reach 30% below 50Hz, which all meet the requirements of the NDIR gas sensor.

A double-end-beam based infrared device fabricated using CMOS-MEMS process

Purpose Thermopile infrared (IR) detectors are one of the most important IR devices. Considering that the surface area of conventional four-end-beam (FEB)-based thermopile devices cannot be effectively used and the performance of this type of devices is relatively low, this paper aims to present a double-end-beam (DEB)-based thermopile device with high duty cycle and performance. The paper aims to discuss these issues. Design/methodology/approach Numerical analysis was conducted to show the advantages of the DEB-based thermopile devices. Findings Structural size of the DEB-based thermopiles may be further scaled down and maintain relatively higher responsivity and detectivity when compared with the FEB-based thermopiles. The authors characterized the thermoelectric properties of the device proposed in this paper, which achieves a responsivity of 1,151.14 V/W, a detectivity of 4.15 × 108 cm Hz1/2/W and a response time of 14.46 ms sensor based on DEB structure. Orginality/value The paper proposed a micro electro mechanical systems (MEMS) thermopile infrared sensor based on double-end-beam structure.

Fabrication and characterization of SiO2/Si heterogeneous nanopillar arrays

This work presents arrays of heterogeneous nanopillars stacked with Si bodies and SiO2 heads for biomedical applications. Novel crossed and overlapped spacer techniques are proposed to fabricate the nanopillar arrays in controllable dimensions. For the nanopillars in the arrays, the minimum spacing, body diameter and head tip-radius reach 100 nm, 23 nm and 11 nm, respectively. The maximum height is 1.2 μm. In addition, because of hydrophilic/hydrophobic selectivity between the SiO2 heads and Si bodies, localized nanoliter water-droplet condensing, fluorescein solution extraction and protein capturing are observed on the SiO2 pillar heads. These experiments demonstrate the great potential of heterogeneous nanopillars in biomedical applications.

Built-in self-calibration of CMOS-compatible thermopile sensor with on-chip electrical stimulus

MEMS devices are expected to be used in a growing number of high-volume and low-cost applications. However because they usually require complex test stimuli rather than simple digital electronic signals as common VLSI systems to verify their specifications, testing and calibration costs have actually become a bottleneck to reduce the overall production cost of MEMS sensors. To address this issue, this paper presents an on-chip scheme to calibrate the responsivity of infrared thermopile temperature sensor with digital control signals. With the proposed method, the responsivity related to the ambient temperature can be calibrated before the target temperature being measured thus to achieve accurate temperature measurement. The proposed self-calibrating thermopile sensor design has been realized by CMOS-compatible process to prove the effectiveness of the self-calibration temperature measurement method.

A low offset chopper amplifier with three-stage nested Miller configuration

A low offset, low noise chopper amplifier for sensor system application is presented. Low 1/f noise is achieved by employing chopper technique, and low offset is achieved by employing residual offset suppression circuit. The open-loop gain is extended using three-stage nested Miller configuration. The chip was implemented in 0.5 μm 2P3M CMOS process. The amplifier is featured by an open-loop gain of 135 dB and a GBW of 3 MHz. The measured offset voltage is 3 μV, and the equivalent input noise power spectrum density at 1 Hz is 96 nV /

Pyroelectric infrared detector based on LiTaO 3 crystal with novelty nanostructured amorphous carbon film

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Optical features of nanowire forests generated using plasma repolymerization

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Hybrid nanopillar forests with broadband high absorptance

This work introduced a novelty MEMS pyroelectric infrared detector based on LiTaO3 (LT) crystal with high absorptivity amorphous carbon film layer. The LT crystal is thined and polished to 100um thickness and double mentaled for electical connection which will be suspened upon rectangle cave of silicon substrate with mental ring. Amorphous carbon(a-C) could be produced by magnetron sputtering on the top of LT layer and nanostructured by Inductively Coupled Plasma(ICP) etching with advantages of lower process temperature and simple fabrication process. Test results shows that the absorptivity of 1.9um a-C was not less than 80% at 2.5–6um wavelength after etching 5 minutes. The performance of developed infrared detector with high absorption rate nanostructured amorphous carbon film is 27 times than that without absorbing layer in theory as well feasible in fabrication process and low cost.

A highly SERS-active and flexible droplet based on carbon-metal composite nanoparticles

In this work, nanowire forests are fabricated by using a plasma repolymerization technique. The fabrication process involves only spin-coating of polyimide and plasma bombardment of the polymer, the whole process is lithography-free, micromachining-compatible and extra simple. Besides, the nanowire forests can further be utilized as nanomasks in reactive ion etching for nanopillar-nanowire composite forests. Optical features of nanowire forests and nanopillar-nanowire composite forests in different wavelength regions are investigated. The high transraittance of nanowire forests in visible-light range implies applications of the forests in transparent devices. Composite forests with a special absorptance peak in range of 8–10 µm implies broader applications of the nanoforests in infrared devices for specific substance sensing.

Candle soot with broadband high absorptance for applications of infrared sensors

In this work, hybrid nanopillar forests (HNFs) are prepared based on a plasma repolymerization technique followed with a metal-nanoparticle deposition step. With these HNFs, an average absorptance as high as 84.1% in a wavelength range of 1.5–25 μm is achieved. The broadband high absorptance of the HNFs is regarded as a combined result from light trapping effect introduced by forests and surface plasmon resonance property induced by metal-nanoparticles. With such a broadband high absorptance, the HNFs are expected to be used as an effective absorber in infrared sensors thus to pursue higher performance, especially in devices like bolometers which are with small dimensions.