Chen Yang Xue

Research of DOA Estimation Based on Single MEMS Vector Hydrophone

The MEMS vector hydrophone is a novel acoustic sensor with a “four-beam-cilia” structure. Based on the MEMS vector hydrophone with this structure, the paper studies the method of estimated direction of arrival (DOA). According to various research papers, many algorithms can be applied to vector hydrophones. The beam-forming approach and bar graph approach are described in detail. Laboratory tests by means of the a standing-wave tube are performed to validate the theoretical results. Both the theoretical analysis and the results of tests prove that the proposed MEMS vector hydrophone possesses the desired directional function.

Design and Analysis of Capacitive Micromachined Ultrasonic Transducers Based on SU-8

In this paper, a new capacitive micromachined ultrasonic transducer (CMUT) is designed by using SU-8 material, and the theory of elastic thin plate is used to deduce the relationship between the pressure and capacitance of the structure. Simulation has been done about SU-8 CMUT by finite element method software ANSYS. The deformation of CMUT under acoustic pressure, the relationship between frequency, thickness and sensitivity, as well as the acoustic impedance and reflection coefficient of SU-8 material also have been studied through the simulation. The results turn out that SU-8 has the advantages of big dynamic range, high sensitivity and small acoustic impedance, so it has broad application in the ultrasonic field.

Engineering the Surface Structure of MoS 2 Nanosheets by Carbon-Doping with Rich Defects to Tune UV-Visible Light Absorption Property

A facile doping method utilizing inexpensive raw materials was proposed to achieve variation in optical bandgap and UV-visible light absorption property of MoS2 nanosheets. Carbon-assistant heating with degreasing cotton has demonstrated the development of carbon-doped MoS2 nanosheets with enhanced rich defects. The results obtained shown that modified MoS2 nanosheets with the lateral width of ~600 nm are exhibited shift of the intensively blue peaks of photo-luminescence (PL) comparing to those MoS2 nanosheets with a lateral dimension of larger than 1 μm. Optical bandgap of the carbon-doped MoS2 nanosheets was found to be broader than that of the pure MoS2 nanosheets and the prepared samples also exhibited a broadband UV-visible light absorption property.

A Monolithic Three-Axis Accelerometer with Low Cross-Axis Sensitivity

A 50,000g three-axis accelerometer using a single proof mass is presented. The sensitive structure is made of a single proof mass and eight cantilever beams. Twelve piezoresistors are placed on the cantilevers symmetrically, which can be used to detect 3-dimensional acceleration. The symmetric placement of the piezoresistors brings the reasonable sensitivity and simultaneously decreases the cross-axis sensitivity significantly. Simulation results show that the sensitivity in X-, Y- and Z-axis are 0.806uV/g, 0.806uV/g and 3.71uV/g respectively with 5V supply and the cross-axis sensitivities are all less than 2.4%, which ensures the high performance of the three-axis accelerometer.

Atomic Layer Deposition of Ultra-Thin Oxide Semiconductors: Challenges and Opportunities

Atomic Layer Deposition (ALD) is an enabling technology which provides coating and material features with significant advantages compared to other existing techniques for depositing precise ultra-thin two-dimensional (2D) nanostructures. ALD provides digital thickness control to the atomic level by depositing film one atomic layer at a time, as well as pinhole-free films even across large and complex areas. The technique’s capabilities are presented on the example of ALD-developed ultra-thin 2D tungsten oxide (WO3) over the large area of standard 4” Si substrates. The discussed advantages of ALD enable and endorse the employment of this technique for the development of hetero-nanostructure 2D semiconductors with unique properties.

Observation of Ferromagnetic Resonance in Magnetic Exchange Force Microscopy (MExFM)

The atomic spin interaction is very important for understanding the superficially magnetic feature of nanostructure at atomic level. Magnetic exchange force microscopy (MExFM) is an innovative means of measuring surface spin force. But it is difficult to separate the surface topography and spin information. We develop the magnetic exchange force microscopy using ferromagnetic resonance (FMR-MExFM). The theoretical and experimental results demonstrate that this method can separate the two kinds of information effectively. Here, in order to obtain the high sensitivity in detecting the ferromagnetic resonance, we fabricate the microwave irradiation device to optimize the position between the device and the cantilever. We have succeeded in observing the ferromagnetic resonance effect and determining its resonant frequency using the homemade microwave irradiation device and the network analyzer. This research is very important for developing FMR-MExFM and novel magnetic sensor, detecting the magnetic information, etc.

Artifacts in KPFM in FM, AM and Heterodyne AM Modes

In this paper, the crosstalk in potential measurements caused by the topographic feedback and the resonance frequency in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM), amplitude modulation (AM) and heterodyne amplitude modulation (heterodyne AM) modes. We showed theoretically that the distance-dependence of the modulated electrostatic force in AM-KPFM is significantly weaker than in FM-and heterodyne AM-KPFMs. We experimentally confirmed that the crosstalk in FM-KPFM and heterodyne AM-KPFM is weak than that in AM-KPFM due to the bigger difference of the modulated frequencies in topographic and potential measurements in FM and heterodyne AM-KPFMs. We also compared the corrugations in the local contact potential difference (LCPD) on the surface of Si (001) show that difference on topographic (potential) images is approximately 15 pm (10 mV) between the faulted and unfaulted parts using heterodyne AM-KPFM, on the other hand, this difference cannot be observed using AM-KPFM mode. Original of this was attributed to the low crosstalk between the topographic and the LCPD measurements in heterodyne AM-KPFM.

Characteristic Research of SOI Rib Waveguide Resonators with SiO2 Deposited

With the extensive research and application of SOI nano-optical ring resonators, the problem of high integration becomes the bottleneck restricting its development. To research the effect of deposited SiO2 insulating layer on the resonance characteristic of SOI nano-waveguid ring cavity while integrating, a rib waveguide ring resonator with 500nm SiO2 insulating layer deposited was designed and fabricated in this paper. By testing the resonance transmission spectrum power of this structure, it is found that SiO2 insulating layer deposited has no effect on the grating vertical coupling efficiency while improves the quality factor to 14.000±1.000.

Integrated-Optic Tenth-Order Micro-Ring Filters in Silicon-on-Insulator

In the paper, it demonstrates highly integrated tenth-order filters in silicon-on-insulator (SOI). The micro-ring resonators have a small radius of 5μm and a very large free spectral range ~ 18nm at 1.55μm communication band. For through port responses, the grating and the high-order optic filters with ten coupled micro-ring resonators are designed and demonstrated, and grating responding well matches with the experiment resonators. Devices are patterned with electron-beam lithography (EBL). And 2μm SiO2 layer is covered on the silicon waveguide, thus reducing the propagation loss in micro-ring resonators.

Analysis of Ultrasonic Radiation Field Based on Linear MEMS Ultrasonic Transducer Array

The analysis of the acoustic field distribution characteristics for the ultrasonic transducer array plays a very important role in both the optimization of the design parameters of the array and the improvement of image quality. In this paper, the acoustic analysis method based on spatial impulse response is studied for the linear MEMS ultrasonic transducer array. The spatial impulse response for the ultrasonic transducer array and the lateral ultrasonic radiation field for the transducer array are obtained by simulation and calculation, and the simulation results are analyzed, which has important implications on the further optimization of MEMS ultrasound transducer design parameters.