Zhenyun Qian

Plasmonic piezoelectric nanomechanical resonator for spectrally selective infrared sensing

Ultrathin plasmonic metasurfaces have proven their ability to control and manipulate light at unprecedented levels, leading to exciting optical functionalities and applications. Although to date metasurfaces have mainly been investigated from an electromagnetic perspective, their ultrathin nature may also provide novel and useful mechanical properties. Here we propose a thin piezoelectric plasmonic metasurface forming the resonant body of a nanomechanical resonator with simultaneously tailored optical and electromechanical properties. We experimentally demonstrate that it is possible to achieve high thermomechanical coupling between electromagnetic and mechanical resonances in a single ultrathin piezoelectric nanoplate. The combination of nanoplasmonic and piezoelectric resonances allows the proposed device to selectively detect long-wavelength infrared radiation with unprecedented electromechanical performance and thermal capabilities. These attributes lead to the demonstration of a fast, high-resolution, uncooled infrared detector with ∼80% absorption for an optimized spectral bandwidth centered around 8.8 μm.

Aluminum Nitride Cross-Sectional Lamé Mode Resonators

This paper demonstrates a new class of AlN-based piezoelectric resonators for operation in the microwave frequency range. These novel devices are identified as cross-sectional-Lamé-mode resonators (CLMRs) as they rely on the piezoelectric transduction of a Lamé mode, in the cross section of an AlN plate. Such a 2-D mechanical mode of vibration, characterized by motion along both the lateral and the thickness directions, is actuated and sensed piezoelectrically through the coherent combination of the e31 and e33 piezoelectric coefficients of AlN. This special feature enables the implementation of CLMRs with high values of electromechanical coupling coefficient. In particular, we experimentally demonstrated kt2 values in excess of 4.6% and 2.5% in CLMRs using, respectively, two or one metallic interdigitated metallic electrodes, and operating around 1 and 2.8 GHz. Furthermore, despite the dependence of the cross-sectional Lamé mode on both the thickness and the width of the AlN plate, lithographic tunability of the resonance frequency, by changing only the in-plane dimensions of the device, can be achieved without a substantial degradation of kt2. The capability of achieving high kt2 and multiple operating frequencies on the same chip, without additional fabrication costs (lithographic tunability of the resonance frequency), makes this technology one of the best candidates for the implementation of multifrequency and low insertion loss filter banks for reconfigurable radiofrequency front ends.

Graphene–aluminum nitride NEMS resonant infrared detector

The use of micro-/nanoelectromechanical resonators for the room temperature detection of electromagnetic radiation at infrared frequencies has recently been investigated, showing thermal detection capabilities that could potentially outperform conventional microbolometers. The scaling of the device thickness in the nanometer range and the achievement of high infrared absorption in such a subwavelength thickness, without sacrificing the electromechanical performance, are the two key challenges for the implementation of fast, high-resolution micro-/nanoelectromechanical resonant infrared detectors. In this paper, we show that by using a virtually massless, high-electrical-conductivity, and transparent graphene electrode, floating at the van der Waals separation of a few angstroms from a piezoelectric aluminum nitride nanoplate, it is possible to implement ultrathin (460 nm) piezoelectric nanomechanical resonant structures with improved electromechanical performance (>50% improved frequency×quality factor) and infrared detection capabilities (>100× improved infrared absorptance) compared with metal-electrode counterparts, despite their reduced volumes. The intrinsic infrared absorption capabilities of a submicron thin graphene–aluminum nitride plate backed with a metal electrode are investigated for the first time and exploited for the first experimental demonstration of a piezoelectric nanoelectromechanical resonant thermal detector with enhanced infrared absorptance in a reduced volume. Moreover, the combination of electromagnetic and piezoelectric resonances provided by the same graphene–aluminum nitride-metal stack allows the proposed device to selectively detect short-wavelength infrared radiation (by tailoring the thickness of aluminum nitride) with unprecedented electromechanical performance and thermal capabilities. These attributes potentially lead to the development of uncooled infrared detectors suitable for the implementation of high performance, miniaturized and power-efficient multispectral infrared imaging systems.

Acoustically actuated ultra-compact NEMS magnetoelectric antennas

State-of-the-art compact antennas rely on electromagnetic wave resonance, which leads to antenna sizes that are comparable to the electromagnetic wavelength. As a result, antennas typically have a size greater than one-tenth of the wavelength, and further miniaturization of antennas has been an open challenge for decades. Here we report on acoustically actuated nanomechanical magnetoelectric (ME) antennas with a suspended ferromagnetic/piezoelectric thin-film heterostructure. These ME antennas receive and transmit electromagnetic waves through the ME effect at their acoustic resonance frequencies. The bulk acoustic waves in ME antennas stimulate magnetization oscillations of the ferromagnetic thin film, which results in the radiation of electromagnetic waves. Vice versa, these antennas sense the magnetic fields of electromagnetic waves, giving a piezoelectric voltage output. The ME antennas (with sizes as small as one-thousandth of a wavelength) demonstrates 1–2 orders of magnitude miniaturization over state-of-the-art compact antennas without performance degradation. These ME antennas have potential implications for portable wireless communication systems.The miniaturization of antennas beyond a wavelength is limited by designs which rely on electromagnetic resonances. Here, Nan et al. have developed acoustically actuated antennas that couple the acoustic resonance of the antenna with the electromagnetic wave, reducing the antenna footprint by up to 100.

Single transistor oscillator based on a Graphene-Aluminum Nitride nano plate resonator

This paper reports on the first demonstration of a high frequency (245 MHz) single transistor oscillator based on Graphene-Aluminum Nitride (G-AlN) nano-plate resonator (NPR). For the first time, a 2-dimensional (2D) electrically conductive graphene layer was integrated on top of an ultra-thin (500 nm) AlN nano-plate and excited into a high frequency contour-extensional mode of vibration by piezoelectric transduction. The resulting ultra-thin, low mass and high frequency G-AlN nanomechanical resonator showed high values of electromechanical coupling coefficient (kt2≈1.8%) and quality factor (Qm≈1000) which enabled the implementation of a low phase noise (-87 dBc/Hz @ 1kHz offset and -125 dBc/Hz floor) single transistor oscillator. The experimental results also demonstrate the great potential of the proposed technology for the implementation of a new class of ultra-sensitive and low noise G-AlN resonant sensors.

Cross-Sectional Lamé Mode Ladder Filters for UHF Wideband Applications

This letter reports on the first demonstration of ladder filters based on the recently demonstrated cross-sectional Lamé mode resonator (CLMR) technology. These filter prototypes show a fractional bandwidth (BW3dB) as high as 3.3% and an insertion loss as low as 0.4 dB. As the resonance frequency of CLMRs can be lithographically controlled without significantly degrading their electromechanical coupling coefficient (k2t), multiple contiguous frequency bands can be covered by this filter technology without adding fabrication complexity. This unique feature addresses one of the most crucial challenges associated with the development of miniaturized mobile platforms adopting carrier-aggregation. Furthermore, the capability of achieving large BW3dB, around lithographically defined center frequencies, enables the fabrication of transmit and receive modules of the next-generation radio-frequency front ends on the same chip without adding fabrication steps.

A 2.8 GHz combined mode of vibration aluminum nitride MEMS resonator with high figure of merit exceeding 45

This paper presents the first demonstration of a high frequency (2.8 GHz), lateral field excited (simple two masks fabrication process), combined lateral-thickness extensional mode of vibration aluminum nitride (AlN) micro-electromechanical systems (MEMS) resonator with unprecedentedly high figure of merit (kt2·Q> 45). For the first time, a single interdigital electrode was employed to excite a high frequency mode of vibration in an AlN plate (1.5 μm thick) by making use of both the d33 and d31 AlN piezoelectric coefficients. The resulting MEMS resonator showed high quality factor, Q~2000, (thanks to the high quality AlN film directly deposit on top of the Silicon substrate) and the highest electromechanical coupling coefficient ever reported for AlN MEMS resonators employing a single electrode, kt2~2.5% (thanks to the coherent combination of d33 and d31 coefficients to transduce one single mechanical mode of vibration).

RF Passive Components Based on Aluminum Nitride Cross-Sectional Lamé-Mode MEMS Resonators

This paper presents a new class of monolithic integrated RF passive components based on the recently developed aluminum nitride (AlN) MEMS cross-sectional Lamé-mode resonator (CLMR) technology. First, we experimentally demonstrate a 920-MHz CLMR showing the values of electromechanical coupling coefficient (k_t²) and quality factor (Q_load) in excess of 6.2% and 1750, respectively. To the best our knowledge, the resulting figure of merit (= Q·k_t²), in excess of 108, is the highest ever reported for AlN-based piezoelectric resonators using interdigitated metallic electrodes (IDTs) and operating in the same frequency range. Second, we report the measured performance of an 870-MHz ladder filter, synthesized using three degenerate CLMRs. This device shows the values of fractional bandwidth (BW_3dB) in excess of 3.8% and an insertion loss of ~1.5 dB. Finally, we report the performance of the first piezoelectric transformer (PT) based on the CLMR technology. This device, dubbed “cross-sectional Lamé-mode transformer,” exploits the high-k_t² of the CLMR technology to achieve high values of open-circuit voltage-gains (G_v) in excess of 39. To the best of our knowledge, such a high G_v-value is the highest ever reported for MEMS-based PTs operating in the microwave frequency range.

Ultra-sensitive NEMS magnetoelectric sensor for picotesla DC magnetic field detection

We report a highly sensitive NEMS DC/low frequency magnetic field sensor consisting of an AlN/FeGaB resonator, with a ΔE effect-based sensing principle. Unlike previously reported magnetic field detection schemes, such as observing induced magnetoelectric voltage, or monitoring impedance, we designed a system to directly measure the reflected output voltage from the sensor as a function of magnetic field. The AlN/FeGaB resonator shows a resonance frequency shift of 3.19 MHz (1.44%), which leads to a high DC magnetic field sensitivity of 2.8 Hz/nT and a limit of detection of 800pT in an unshielded, room temperature and pressure, lab environment.

High resolution calorimetric sensing based on Aluminum Nitride MEMS resonant thermal detectors

This paper presents a high temperature resolution (994.5 μK/Hz1/2 in a 50 Hz measurement bandwidth) micro-calorimetric sensor based on a high frequency (134.5 MHz) Aluminum Nitride (AlN) nano-plate resonator (NPR) overlapped by a freestanding reaction chamber separated by a micro-scale air gap (~50 μm). For the first time, the unique thermal detection capabilities of the AlN NPR technology are exploited to devise a calorimetric sensor with superior performance. Efficient heat transfer from the reaction chamber to the thermal detector is achieved by scaling the air gap between them. By taking advantage of the large thermal resistance (2.64 × 104 K/W) of the AlN NPR and the reduced air gap, high heat transfer efficiency (ratio between the temperature of the resonator and the one of the reaction chamber) of 33% is achieved. The effectiveness of the fabricated prototype is experimentally verified by monitoring an exothermic reaction between Hydrochloric Acid (HCl) and Ammonium Hydroxide (NH4OH). A high sensitivity of 9.62 kHz/M and detection limit of ~120 μM/Hz1/2 are achieved for the first device prototype.