Zhenyun Qian

This paper presents a high-performance infrared sensor based on a Scandium Aluminum Nitride (ScAlN) laterally vibrating resonator integrated with plasmonic absorbers for spectrally selective IR absorption. The proposed technology enables fast, compact, and high-resolution IR detection, making it ideal for the implementation of mobile gas-spectroscopy systems for environmental monitoring over large areas for extended periods. The sensor was designed to exhibit high IR absorptance at $4.5~\mu $ m, matching the absorption peak of N₂O. The resonant sensor experimentally shows an outstanding mechanical quality factor ( $Q_{m}$ ) of 2000, a 2.7% electromechanical coupling ( $k_{t}^{2}$ ), a high responsivity of 0.9 Hz/nW, a fast response of 6 ms and a low NEP of 320 pW/ $\mathrm {Hz}^{1/2}$ . While we focus on $4.5~\mu $ m in this system, the absorption wavelength is lithographically tunable, enabling the fabrication of multi-gas sensors on the same chip without using additional masks. A key innovation in this work compared to prior resonant IR detectors is the use of a novel material stack: Aluminum Nitride (AlN) as the dielectric in the Metal–Insulator–Metal plasmonic absorbers, combined with 30%-doped Scandium Aluminum Nitride (ScAlN) for the acoustic resonant cavity. This combination enhances sensor performance by taking advantage of the higher thermal resistance of ScAlN, as well as the higher temperature coefficient of frequency (TCF) of AlN compared to silicon dioxide (SiO₂). SiO₂ is traditionally used for IR absorption due to its optical properties; however, it is also characterized by a positive TCF, thereby degrading the thermal response of the resonator. In this work, the influence of geometrical parameters is experimentally investigated in hundreds of devices. The effect of tethering configurations and anchors’ width-to-length ratios on the sensor’s quality factor, thermal isolation, time response, and TCF is reported. Following optimization, the best-performing sensors are vacuum-packaged to enhance thermal isolation and improve response to IR. The device’s IR response is tested both in open-loop configuration with a vector network analyzer and in closed-loop within an oscillator circuit optimized for reduced phase noise. [2025-0145]

This paper reports on zero standby power human presence detectors based on an optimized micromechanical photoswitch (MP) with a metasurface-enhanced long wavelength infrared (LWIR) absorber, increased thermal sensitivity, reduced bias voltage, and a wide field-of-view. The reported device shows the capability of detecting a human body around 2.65 m and human hand around 1 m distance using low bias voltages without using any focal lenses. Existing wireless motion detectors based on pyroelectric IR sensors consume ∼100 μW power on standby continuously and produce frequent false alarms due to non-relevant objects (such as moving cars and falling leaves), which inevitably drains the battery in a relatively short period of time (typically less than a year). The demonstrated zero-power sensor here exploits the LWIR energy emitted from a human body for true presence detection without consuming any electrical power on standby. The first experimental demonstration of human body detection with vacuum packaged MP at a distance comparable to commercial motion detectors is enabled by the optimization of an MP in terms of thermomechanical performance (thermal sensitivity ∼1.5 nm/nW, stiffness ∼0.2 nN/nm, and threshold ∼10 nW) and IR absorption (η > 60% in λ = 6-14 μm, field-of-view ∼110 °). The new broadband LWIR metasurface absorbers improve the structural symmetry of MP by matching the material stacks of reflecting and absorbing heads. This improvement allows the MP to work with lower voltage bias thus, making it compatible with low-power electronics.

This paper presents an interesting new method for measuring infrared (IR) radiation using a micromechanical photoswitch (MP). By leveraging the event-driven narrowband IR detection capability of an MP, electrostatic pull-in, and a novel integrated thermomechanical feedback mechanism, we show for the first time a zero-standby power IR sensor that can not only detect above-threshold IR power levels (>600 nW), but also generates an oscillating electromechanical pulse waveform whose frequency is a function of the incident IR power level. The device design, the theoretical model for the proposed idea, and the experimental demonstration of the mechanism are shown. The unique capability of zero-standby power IR detection and frequency-tunable AC waveform generation from a constant input signal (IR radiation) without the need for additional electronics promises to enable new functionalities for such remote wake-up sensors beyond simply detection, with potential uses in microrobotics and low-power computing.

This paper reports on the demonstration of ultrafast (thermal time constant, τ ∼ 166 μs) and high resolution (noise equivalent power, NEP ∼ 549 pW/Hz^1/2) thermal detectors based on high quality factor 50-nm thick aluminum nitride (AlN) piezoelectric resonant nanoplates. Here we show that by employing nanoscale (30 nm) aluminum anchors, both high thermal resistance (R_th ∼ 1.1 × 10⁶ K/W) and high quality factor (Q ∼ 1000) can be achieved in greatly scaled AlN nanoplate resonators. Furthermore, the absorptance of such ultrathin AlN resonators was characterized, in mid-wavelength infrared region showing an average absorptance of ∼36% from 2.75 μm to 6.25 μm. These unique features were exploited for the experimental demonstration of AlN NEMS resonant thermal detectors with greatly reduced thermal capacitance and over doubled figure of merit [FoM = 1/(NEP × τ)] compared to what was previously achieved by the same technology.

This paper reports on the first demonstration of ultra-fast (thermal time constant, τ ~80 μs) and high resolution (noise equivalent power, NEP ~656 pW/Hz ^1/2 ) infrared detectors based on high quality factor 50-nm thick aluminum nitride (AlN) piezoelectric resonant nano-plates. For the first time, we show that by employing nanoscale (30 nm) aluminum anchors, both high thermal resistance (R _th ~9.2×10 ⁵ K/W) and high quality factor (Q ~1000) can be achieved in greatly scaled AlN nano-plate resonators. Furthermore, we experimentally demonstrate that the resonant structures are capable of efficiently absorbing short-to mid- wavelength infrared (absorption, η ~47%, for blackbody radiation at 625 °C) without any additional absorber. These unique features are exploited for the first experimental demonstration of AlN NEMS resonant infrared detectors with highly reduced area (down to 20×22 μm ² , comparable to the ones of state-of-the-art microbolometers) and over 4x improved figure of merit (FoM=1/(NEP·τ)) compared to what previously achieved by the same technology.

We experimentally demonstrate Aluminum Nitride (AlN) cross-sectional Lamé mode resonators (CLMRs) operating in the microwave frequency range and showing high Qkt ² products (FoM) in excess of 85. Such feature enables low motional resistance (Rm) values (37 Ω) in CLMRs characterized by low static capacitance (Co) approaching 66 fF. In addition, the ability of CLMRs to simultaneously achieve high kt ² (> 4%) and a lithographic frequency tunability (> 260 MHz around 900 MHz) is experimentally demonstrated, for the first time, in this work. Such important feature renders CLMRs promising candidates to replace off-chip Surface Acoustic Wave (SAW) devices in lithographically defined filters for next-generation wireless communication platforms.

We demonstrate the first ladder filter based on the use of the recently demonstrated cross-sectional Lamé mode resonators (CLMRs). This device shows a fractional bandwidth (BW _3db ) as high as 3.3% while enabling an insertion-loss as low as 2.5 dB. As the resonance frequency of CLMRs can be controlled lithographically without significantly degrading their electromechanical coupling coefficient (k _t ² ), this novel filtering technology permits to cover multiple frequency bands without adding fabrication complexity. In particular, as demonstrated in this work, this feature enables the use of CLMFs in platforms adopting carrier-aggregation. In addition, the capability of achieving large BW _3dB around lithographically defined center frequencies permits to build transmitter and receiver modules of next-generation Radio-Frequency (RF) front-ends on the same chip and without adding fabrication steps.