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Conventionally, mechanical resonators exhibit evident degradation in quality factor and large frequency fluctuation at elevated temperatures above room temperature. Here, we show that the quality factor of up to 10 5 of a highly stressed GaN on Si nanomechanical resonators experiences little change as temperature increasing to 600 K and the temperature coefficient of the resonance frequency (TCF) is as low as several ppm/K, several times lower than those of the conventional GaN mechanical resonators. The high quality factor and low TCF at high temperatures are attributed to the high stress and the geometrical nonlinearity of dynamical strain in the GaN resonator, where the dissipation caused by the change of the material properties with the increasing temperature is compensated by the increased stiffness. This observation violates the universality of thermal energy dissipation in mechanical resonators. The results provide a universal strategy for engineering nanomechanical resonators with ultrahigh sensitivity and ultralow noise. [ABSTRACT FROM AUTHOR]

The authors report the enhancement of the magnetic sensitivity of single-crystal diamond (SCD) MEMS magnetic sensor, which is composed of a SCD cantilever integrated with a magneto-strictive Galfenol (FeGa) thin film. To improve the magnetic sensing properties from room temperature to high temperatures, different interlayers of Ti film, WC film, and WC/Ti film are inserted between the SCD cantilevers and the FeGa thin films in the SCD-MEMS magnetic sensors. The thermal-stability of the microstructures, phase structures, and magnetic properties of the FeGa thin films are greatly enhanced by these interlayers. The FeGa thin films within the FeGa/SCD, FeGa/Ti/SCD, FeGa/WC/SCD, and FeGa/Ti/WC/SCD structures maintain high thermal-stability in surface morphologies, roughness, phase structures, and magnetic properties under the annealing temperature up to 573 K, 773 K, 573 K, and 673 K, respectively. The magnetic sensor with the FeGa/SCD structure has the weakest magnetic sensitivity of 1.96 Hz/mT @573 K and the FeGa/WC/Ti/SCD structure hosts the highest magnetic sensitivity of 75.40 Hz/mT @673 K. The present work provides a strategy to tailor the magnetic sensing properties of SCD MEMS for the applications under extreme conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

As an ultrastable material, single‐crystal diamond (SCD) has been proven to have extraordinary reliability in the application of microelectromechanical systems (MEMS). To satisfy the requirements of high sensitivity and high stability of magnetic sensors, SCD MEMS resonators integrated with TbDyFe thin film are successfully fabricated by radio‐frequency magnetron sputtering. The device is thermally stable and the sensing performance is improved after annealing at 550 °C for 3 h. A high magnetic sensitivity of 5.34 Hz mT−1 is achieved. The estimated minimum detectable force reaches 1.65 × 10−14 N due to the advantage of giant magnetostriction of the TbDyFe thin film. The realization of SCD MEMS magnetic sensor demonstrates a visible progress in the field of magnetic sensing and indicates a foreseeable potential of SCD MEMS in the application of fast, small, and energy‐efficient sensors. [ABSTRACT FROM AUTHOR]

We report on a highly sensitive gallium nitride (GaN) micro-electromechanical (MEMS) resonator with a record quality factor (Q) exceeding 105 at the high resonant frequency (f) of 911 kHz by the strain engineering for the GaN-on-Si structure. The f of the double-clamped GaN beam bridge is increased from 139 to 911 kHz when the tensile stress is increased to 640 MPa. Although it is usually regarded that the energy dissipation increases with increasing resonant frequency, an ultra-high Q-factor which is more than two orders of magnitude higher than those of the other reported GaN-based MEMS is obtained. The high Q-factor results from the large tensile stress which can be intentionally introduced and engineered in the GaN epitaxial layer by utilizing the lattice mismatch between GaN and Si, leading to the stored elastic energy and drastically decreasing the energy dissipation. The developed GaN MEMS is further demonstrated as a highly sensitive mass sensor with a resolution of 10−12 g/s through detecting the microdroplet evaporation process. This work provides an avenue to improve the f × Q product of the MEMS through an internally strained structure. [ABSTRACT FROM AUTHOR]

Single-crystal diamond (SCD) is a promising material for micro-electromechanical system (MEMS) devices to achieve high performance and reliability due to its prominent mechanical and physical properties. However, the application of SCD MEMS has not been practically achieved due to the lack of device concept for SCD MEMS. Here, the SCD MEMS resonator based magnetic sensor is successfully realized with integrating of a large magneto-strictive galfenol film on SCD mechanical resonator with high performance. It is concluded that SCD provides a suitable substrate for galfenol film with excellent magnetic properties. Along with the high-quality factor of the SCD MEMS resonator, a high magnetic field sensitivity of 4.83 Hz/mT and an extremely low detectable force of 2.14 × 10−12 N are achieved. Based on the experimental results, the estimated minimum detectable force, magnetic field and energy reach 1.76 × 10−14 N, 1.42 × 10−10 T and 8.4 × 10−29 J. The successful fabrication of SCD MEMS magnetic sensor provides a promising strategy for broadening the application of SCD MEMS with merits super to other ones, such as nanoscale to microscale spatial resolution, wide-range magnetic field sensing, high sensitivity, high temperature operation, and facile integration with CMOS. Single crystal diamond MEMS cantilever resonator integrating with a large magneto-strictive galfenol film is demonstrated for magnetic sensor. The magnetic sensor shows a high magnetic field sensitivity of 4.83 Hz/mT and an extremely low detectable force of 2.14 × 10−12 N. The current work of successful fabrication of SCD MEMS magnetic sensor provides a promising strategy for broadening the application of SCD MEMS with merits super to other ones, such as nanoscale to microscale spatial resolution, wide-range magnetic field sensing, high sensitivity, high temperature operation, and facile integration with CMOS. Image 1 [ABSTRACT FROM AUTHOR]

• High quality diamond-on-diamond cantilevers are fabricated by smart-cut method. • Stress in cantilevers is analyzed by curvature, Raman shift and resonance frequency. • Resonance frequencies are little influenced despite the residual stress. • Single crystal diamond cantilevers are ideal system for microscopic application. Micro-cantilever beams have been widely used for surface sensing applications as well as atomic force microscope. However, surface stress appears in cantilever beams due to a variety of factors such as the absorption of molecules, temperature variations, materials imperfectness, and the fabrication process. Single-crystal diamond (SCD) has been regarded as an ideal material for cantilever sensors through the surface effect due to the outstanding mechanical rigidity and chemical inertness. In this paper, the authors report on the SCD cantilever beams fabricated by a smart-cut method with high quality factors up to 14 000 and stress characterization by surface geometry curvature observation and Raman microscopy. Although both surface geometry profile and Raman shift show the existence of surface stress in the SCD cantilever beams, the resonance properties are little influenced and maintain excellent rigidity and high quality. Therefore, the SCD-on-SCD resonator provides a promising platform for high-reliability microscopy applications. [ABSTRACT FROM AUTHOR]