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An ultrasensitive single-axis out-of-plane micro optical electro mechanical system (MOEMS) accelerometer with a relatively low cross-axis sensitivity based on a designated micromachined sensing structure and grating interferometry cavity is proposed. While seeking to achieve high performances, we investigated and optimized the design of the mechanical structure, with tensile stress in the flexure close to the ultimate yield strength of monocrystalline silicon. Expressions for acceleration-displacement sensitivity are given and compared with the results of finite-element-method simulations. The highly symmetric accelerometer was fabricated through a particular fabrication process on a specific double-device-layer silicon-on-insulate wafer. The acceleration-displacement sensitivity of the optimal sensing structure, as obtained from static acceleration measurement, was 158.20~\mu \textm /g and outperforms its previously reported counterparts. Experimental results revealed that the MOEMS accelerometer with an optimal design achieved an acceleration sensitivity of 2485 V/g with a resonant frequency of 34.5 Hz and a noise level of 185.8 ng/(Hz) ^0.5 , corresponding to a resolution of 1~\mu \textg , as well as a cross-axis sensitivity of 3.48%/0.1 g, which is one order smaller than the conventional one. The proposed design may pave the way for the applications that require extremely high sensitivity, low cross-axis sensitivity, and comparatively low-frequency response, such as seismology and microgravity detection. [2017-0034] [ABSTRACT FROM PUBLISHER]

This paper discusses the error analysis and optimization of a lateral deformable NEMS zeroth-order grating transducer based on an anomalous diffraction phenomenon, namely Wood's type anomaly, in which tiny changes in the displacement of the nanostructured grating elements lead to a dramatic increase or decrease of the optical reflection amplitude. With this special feature, this structure is ideal to measure very small displacement. However, parameters such as wavelength, period, duty ratio play very important roles in the performance of the device. In this paper, the performance of the structures with different parameter settings is analyzed and the original structure is optimized through 3-D Finite Difference Time Domain method (FDTD). Simulation demonstrates the new structure is of higher sensitivity, namely 0.705%/nm. Moreover, in order to enlarge the tiny size of the original structure which is closely related to the incident wavelength, the wavelength of incident light is changed into longer ones, e.g. 1053 nm, 1310 nm, and 1530 nm. The calculation predicts the optimized structure corresponding to 1530 nm not only has extinction ratio higher than the original one, namely 96% but also twice larger size, namely twice less strict demand for processing precision, which makes them possible to fabricate with current surface micromachining processing similar to that used for the fabrication of polysilicon MEMS. Besides, structures of several visible incident wavelengths, such as 532 nm, 632.8 nm, 670 nm, and 753 nm, are also analyzed and optimized, which gives great convenience to the installation and calibration of such device as well as observation of its performance. All the calculated data enables us to apply the structure into fields required for different sensitivities with different grating designs and thus broadens the further usage of such novel structure, as structures of different parameters are of different sensitivities and signal strengths. In addition, a tolerance analysis of the device in terms of fabrication, illumination, alignment is discussed in detail to get a guidance of successful realization of an actual device. Especially, during the analysis an unexpected performance of the device is discovered, in which the signal of the devices corresponding to 1530 nm changes into pulse signal with slop of 2.292%/nm, i.e. 0.36 dB/nm when the air gap is reduced to 300 nm, indicating sensitivity over four times higher than that of the original one, namely 0.5%/nm, i.e. 0.04 dB/nm. [ABSTRACT FROM AUTHOR]

In the above article , the content of this article remains untouched. Only is rectified. The stiffness of the proposed MOEMS accelerometer listed in should be half of that value, which is 0.56 N/m. [ABSTRACT FROM AUTHOR]

Interferometric optomechanical accelerometers provide superior resolution, but the application is limited due to the non-ambiguity range that is always less than half of the wavelength, which corresponds to the order of mg. This paper proposes a novel acceleration measurement method based on synthetic wavelength and single wavelength superheterodyne interferometry to address this issue. Two acousto-optical modulators and several polarizers are introduced to the two-wavelength interferometry to create four beams with different frequencies and polarization states, and two ultra-narrow bandwidth filters are used to realize the single wavelength measurement simultaneously. This technique offers the possibility to expand the non-ambiguity range without compromising the high resolution. Also, the superheterodyne phase measurement and the corresponding processing algorithm are given to enable real-time measurement. A prototype is built and the preliminary experimental results are compared with the simulation results, showing good agreement. The results prove an estimated acceleration measurement resolution of around 10 μg and a non-ambiguity range of larger than 200 mg, which is more than 100 times that of the single wavelength-based optical accelerometer. [ABSTRACT FROM AUTHOR]

Although the Lissajous frequency modulated (LFM) mode can improve the long-term and temperature stability of the scale factor (SF) for mode mismatch MEMS gyroscopes, its SF nonlinearity poses a significant limitation for full-scale accuracy maintenance. This paper examines the interaction effects among stiffness coupling, system phase delay, readout demodulation phase shift, and velocity amplitude mismatch within the control process. Based on the completion of frequency difference control and demodulation phase matching, we clarify that the remaining stiffness coupling and residual system phase error are the primary factors influencing SF nonlinearity. Furthermore, SF nonlinearity is reduced through error compensation. On one hand, this paper suppresses stiffness coupling through the observation of the instantaneous frequency difference and the application of the quadrature voltage. On the other hand, system phase error is compensated by observing the amplitude control force and tuning the reference in the Phase-Locked Loops (PLLs). Subsequent simulations of these methods demonstrated a remarkable 97% reduction in SF nonlinearity within the measurement range of ±500°/s. In addition, an observed rule dictates that maintaining a sufficiently large frequency split effectively constrains the SF nonlinearity. [ABSTRACT FROM AUTHOR]

[Display omitted] High-mobility van der Waals ambipolar semiconductors are promising in logic and reconfigurable circuits, integrated optoelectronic circuits, due to the excellent gate-controlled capability and effectively tunability of major charge carriers by electrostatic field. Controllable growth of high-quality ambipolar semiconductors with high mobility and stability is highly glamorous and indispensable for further research. Here, we demonstrate a straightforward space-confined chemical vapor deposition (CVD) method to synthesize high-quality quasi-one-dimensional (1D) tellurium (Te) nanoribbons (NRs). By introducing H 2 into the gas flow, endothermic compound H 2 Te was generated from the reaction of liquid Te with H 2 , and consequently decomposed into elemental Te at low temperature. Further, the Te NRs have been utilized for in-situ fabrication of field-effect transistors (FETs) without transferring process. Ambipolar features are achieved using nickel (Ni) as an ohmic contact. More importantly, the mobilities of the Te NR transistor for hole/electron are as high as 1755/28.6 cm2V−1s−1 and 4024/278 cm2V−1s−1 at room temperature and under a temperature below 20 K, respectively. Our findings confirm the novel strategy for synthesizing 1D elemental semiconductors and their applications with ambipolar behaviors. [ABSTRACT FROM AUTHOR]

There is a constraint between the dynamic range and the bandwidth of MEMS accelerometers. When the input acceleration is comparatively large, the squeeze film damping will increase dramatically with the increase in the oscillation amplitude, resulting in a decrease in bandwidth. Conventional models still lack a complete vibration response analysis in large amplitude ratios and cannot offer a suitable guide in the optimization of such devices. In this paper, the vibration response analysis of the sensing unit of an accelerometer in large amplitude ratios is first completed. Then, the optimal design of the sensing unit is proposed to solve the contradiction between the dynamic range and the bandwidth of the accelerometer. Finally, the results of the vibration experiment prove that the maximum bandwidth can be achieved with 0~10g external acceleration, which shows the effectiveness of the design guide. The new vibration analysis with the complete model of squeeze film damping is applicable to all sensitive structures based on vibration, not limited to the MEMS accelerometer studied in this thesis. The bandwidth optimal scheme also provides a strong reference for similar structures with large oscillation amplitude ratios. [ABSTRACT FROM AUTHOR]

Squeeze film air damping is a significant factor in the design of MEMS devices owing to its great impact on the dynamic performance of vibrating structures. However, the traditional theoretical results of squeeze film air damping are derived from the Reynolds equation, wherein there exists a deviation from the true results, especially in low aspect ratios. While expensive efforts have been undertaken to prove that this deviation is caused by the neglect of pressure change across the film, a quantitative study has remained elusive. This paper focuses on the investigation of the finite size effect of squeeze film air damping and conducts numerical research using a set of simulations. A modified expression is extended to lower aspect ratio conditions from the original model of squeeze film air damping. The new quick-calculating formulas based on the simulation results reproduce the squeeze film air damping with a finite size effect accurately with a maximum error of less than 1% in the model without a border effect and 10.185% in the compact model with a border effect. The high consistency between the new formulas and simulation results shows that the finite size effect was adequately considered, which offers a previously unattainable precise damping design guide for MEMS devices. [ABSTRACT FROM AUTHOR]

The Micro-Opto-Electro-Mechanical Systems (MOEMS) accelerometer is a new type of accelerometer that combines the merits of optical measurement and Micro-Electro-Mechanical Systems (MEMS) to enable high precision, small volume, and anti-electromagnetism disturbance measurement of acceleration, which makes it a promising candidate for inertial navigation and seismic monitoring. This paper proposes a modified micro-grating-based accelerometer and introduces a new design method to characterize the grating interferometer. A MEMS sensor chip with high sensitivity was designed and fabricated, and the processing circuit was modified. The micro-grating interference measurement system was modeled, and the response sensitivity was analyzed. The accelerometer was then built and benchmarked with a commercial seismometer in detail. Compared to the previous prototype in the experiment, the results indicate that the noise floor has an ultra-low self-noise of 15 ng/Hz1/2. [ABSTRACT FROM AUTHOR]

• A preliminary chip-scale packaged design of an optical accelerometer is proposed. • The relationship between material properties and thermal deformation is obtained. • A guide for the design of accelerometers with high thermal stability is proposed. Accelerometers based on optical cavity have a complicated situation of thermal deformation, which significantly influences the measurement results. In order to minimize the thermal drift of the accelerometer, a preliminary multilayer structure package design is proposed. A simplified finite element model of this design is built and further optimized in consideration of boundary conditions to compare the thermal drift of the prototype of the accelerometer. The theoretical calculations of the temperature distribution and structure deformation successfully verify the correctness of the simulation results. The relationships between the material properties and the thermal deformation, as well as the vibration of optical path length are obtained via simulation and theoretical calculation; thus, providing a characteristic formula of the optical path length and the material properties. The relationships can be considered a strong guide for the design of multilayer-structure accelerometers with high temperature stability. [ABSTRACT FROM AUTHOR]