A. B. Randles

A nanoelectromechanical systems actuator driven and controlled by Q-factor attenuation of ring resonator

In this Letter, an optical gradient force driven Nanoelectromechanical Systems (NEMS) actuator, which is controlled by the Q-factor attenuation of micro-ring resonator, is demonstrated. The actuator consists of a tunable actuation ring resonator, a sensing ring resonator, and a mechanical actuation arc. The actuation displacement can reach up to 14 nm with a measured resolution of 0.8 nm, when the Q-factor of the ring resonator is tuned from 15 × 103 to 6 × 103. The potential applications of the NEMS actuator include single molecule manipulation, nano-manipulation, and high sensitivity sensors.

Dual mode acoustic wave sensor for precise pressure reading

In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm–50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of −50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellatio...

Viscosity and density decoupling method using a higher order Lamb wave sensor

Viscosity and density are two important physical parameters of liquid. Such parameters are widely used for label-free chemical detection. Conventional technologies employ acoustic wave sensors to detect viscosity and density. In these sensors, the liquid under test directly contacts with the surface of the sensor. The produced acoustic wave in the sensor leaks to the adjacent liquid layer, causing a shift in the resonance frequency of the sensor. However, such sensors are not able to separately measure the viscosity and density because these two parameters jointly affect the shift of frequency. Although some indirect methods for decoupling these two parameters have been investigated, either dual-device or simultaneous measurement of frequency and attenuation is required. In this paper, a novel AlN based acoustic wave sensor is developed for decoupling viscosity and density. Multiple higher order modes of Lamb waves are generated in this sensor and employed to interact with the adjacent liquid under test. The frequency change of two unique modes (mode C and mode D) has been found in a linear relationship with viscosity and density, respectively. With this unique feature, viscosity and density of a liquid can be distinguished by a single device, which is promising for potential industrial applications, label-free chemical detection and clinical diagnosis.

CMOS-compatible ruggedized high-temperature Lamb wave pressure sensor

This paper describes the development of a novel ruggedized high-temperature pressure sensor operating in lateral field exited (LFE) Lamb wave mode. The comb-like structure electrodes on top of aluminum nitride (AlN) were used to generate the wave. A membrane was fabricated on SOI wafer with a 10 µm thick device layer. The sensor chip was mounted on a pressure test package and pressure was applied to the backside of the membrane, with a range of 20–100 psi. The temperature coefficient of frequency (TCF) was experimentally measured in the temperature range of −50 °C to 300 °C. By using the modified Butterworth–van Dyke model, coupling coefficients and quality factor were extracted. Temperature-dependent Youngs modulus of composite structure was determined using resonance frequency and sensor interdigital transducer (IDT) wavelength which is mainly dominated by an AlN layer. Absolute sensor phase noise was measured at resonance to estimate the sensor pressure and temperature sensitivity. This paper demonstrates an AlN-based pressure sensor which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications.

Diaphragm shape effect on the sensitivity of surface acoustic wave based pressure sensor for harsh environment

Aluminum Nitride (AlN) based surface acoustic wave (SAW) pressure sensors for harsh environment applications are of great interest in recent years. Such sensor employs a thick diaphragm (∼50 μm) to endure the high pressure, but this seriously limits the sensitivity of these devices. Understanding of the working mechanism and the effect of geometrical parameters will yield the design principles to achieve improved sensitivity. In this letter, the effect of diaphragm on the performance of SAW pressure sensors is studied. AlN based SAW resonators on (100) wafer with different diaphragm shapes are fabricated, packaged, and characterized. Pressure coefficient of frequency (PCF) of pressure sensors with circular diaphragm, rectangular diaphragm (small aspect ratio) and rectangular diaphragm (large aspect ratio) is found to be 0.071 ppm/psi, 0.038 ppm/psi, and −0.171 ppm/psi, respectively. The longitudinal and lateral strains along the SAW propagation direction (〈100〉 direction) have the opposite effects on the ...

Uncooled resonant infrared detector based on aluminum nitride piezoelectric film through charge generations and lattice absorptions

This Letter demonstrates an aluminum nitride (AlN) based uncooled resonant infrared (IR) detector utilizing the photo-sensitive and piezoelectric properties of polycrystalline AlN. The AlN Lamb wave mode resonator is found responsive to IR illuminations by showing a decrease in the S21 magnitude instead of a resonant frequency shift. A −0.08 dB shift of S21 magnitude was observed for an IR incident power of 647 nW, which translates to a responsivity of 124 kdB/W. Photoresponse is proposed for the IR sensing mechanism through additional charge carriers generation rather than thermal effects.

Enhancement of the Transmission of Piezoelectric Micromachined Ultrasonic Transducer With an Isolation Trench

A new piezoelectric micromachined ultrasonic transducer (pMUT) with an isolation trench between cells was proposed to improve the output pressure. A 2-D finite-element model was utilized to evaluate and compare the performance of the conventional design with fully clamped boundary and the trench design. It shows that the trench design can improve the membrane displacement or output pressure of pMUTs without a significant change in the resonant frequency; 8 × 8 aluminum nitride (AlN)-based pMUTs arrays with fully clamped boundary design and the isolation trench were fabricated and characterized. An impulse response of the pMUTs array was first employed to determine the resonant frequency. A 200-cycle burst at the resonant frequency was then delivered to pMUTs and the acoustic output pressure was measured by a hydrophone. The trench design could increase the output pressure by ~76% with a shift of its center frequency by only 0.03 MHz. The nonlinear relationship between pressure output and applied high voltage still exists in the trench design. The presence of residual stress in the membrane, and substrate during fabrication was found to have little impact on the displacement and resonant frequency of pMUT. In summary, the presence of isolation trench can reduce the deflection-induced tensile stress on the edge of the membrane and subsequently improve the performance of pMUTs.

ALN-based piezoelectric resonator for infrared sensing application

This paper reports a highly sensitive aluminum nitride (AlN) based resonant uncooled infrared (IR) detector utilizing photo-sensitive and piezoelectric properties of polycrystalline AlN. The design, fabrication, and IR sensing characterization of the device are presented. Instead of resonant frequency shift, S21 magnitude shift was observed upon IR illumination under both vacuum and ambient measurements. Thus, photoresponse mechanism was proposed rather than thermal effect. An AlN resonator operating at 2.336 GHz with a quality factor (Q) of 830 exhibits an IR responsivity and detectivity of 166 kdB/W and 1.41 × 107 cm√Hz/W, respectively.

A tunable laser based on nano-opto-mechanical system

This paper presents an external cavity tunable laser based on nano-opto-mechanical system by integrating the gain laser diode and the opto-mechanical ring resonators on a silicon chip. An optical force controlled tuning approach is demonstrated whereby the lasing light itself adjusts the lasing wavelength by controlling the mechanical displacement of the silicon ring resonator. In the experiments, a 24-nm wavelength tuning is realized due to a deflection of 14-nm. The optomechanical wavelength tuning coefficient is 214 GHz/nm. The demonstrated device has potential applications for optical communication system, pulse trapping/release, and chemical sensing, with easy on-chip integration on a silicon platform.

An all optical shock sensor based on buckled doubly-clamped silicon beam

In this paper, an all optical shock sensor based on a buckled doubly-clamped silicon beam is demonstrated. A buckled silicon beam is in the middle of two ring resonator and it has two stable positions. The silicon beam encounters a snap-through process upon a shock force, which can be monitored by measuring the resonance wavelength of the ring resonators. During experiment, a 0.15 nm wavelength is observed for a > 50 g shock. It has merits such as fast response, low power consumption and immunity to electromagnetic interference. It can be applied to inertial navigation system and automotive industry.