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An integrated MEMS accelerometer has been designed and fabricated. The device, which is based on the piezoresistive effect, accomplishes the detection of three components of acceleration by using piezoresistors to compose three Wheatstone bridges that are sensitive to the only given orientation. The fabrication of the accelerometer is described, and the theory behind its operation developed. Experimental results on sensitivity, cross-axis-coupling degree, and linearity are presented. The sensitivity of X, Y and Z were 5.49 mV/g, 5.12 mV/g and 4.82 mV/g, respectively; the nonlinearity of X, Y and Z were 0.01%, 0.04% and 0.01%, respectively; the cross-axis-coupling factor of X axis to Y axis and Z axis are 0.119% and 2.26%; the cross-axis-coupling factor of Y axis to X axis and Z axis are 0.157% and 4.12%; the cross-axis-coupling factor of Z axis to X axis and Y axis are 0.511% and 0.938%. The measured performance indexes attain accurate vector-detection in practical applications, and even at a navigation level. In conclusion, the accelerometer is a highly integrated sensor.

A kind of piezoresistive ultrasonic sensor based on MEMS is proposed, which is composed of a membrane and two side beams. A simplified mathematical model has been established to analyze the mechanical properties of the sensor. On the basis of the theoretical analysis, the structural size and layout location of the piezoresistors are determined by simulation analysis. The boron-implanted piezoresistors located on membrane and side beams form a Wheatstone bridge to detect acoustic signal. The membrane-beam microstructure is fabricated integrally by MEMS manufacturing technology. Finally, this paper presents the experimental characterization of the ultrasonic sensor, validating the theoretical model used and the simulated model. The sensitivity reaches −116.2 dB (0 dB reference = 1 V/μbar, 31 kHz), resonant frequency is 39.6 kHz, direction angle is 55°.

The design, fabrication and packaging of a type of MEMS piezoresistive ultrasonic transducer array are introduced. The consistency of the resonance frequency and the sensitivity of the array are tested. Moreover, we detect the directivity and the multi-target identification ability of the array. The results of the consistency of the resonance frequency and the sensitivity show that there is a gap between the practical and theoretical results. This paper analyzes this problem in detail and points out the direction of improvement. As for the directivity, the actual result is consistent with the theoretical one. The results of multiple target distinguishing tests demonstrate that the smallest resolution angle of the array is 5.72° when the distance between the sensor array and measured objects is 2 m.

With the springing up of the MEMS industry, research on accelerometers is focused on miniaturization, integration, high reliability, and high resolution, and shares extensive application prospects in military and civil fields. Comparing with the traditional single cantilever beam structure or "cantilever-mass" structure, the proposed structure of "8-beams/mass" with its varistor completely symmetric distribution in micro-silicon piezoresistive triaxial accelerometer in this paper has a higher axial sensitivity and smaller cross-axis sensitivity. Adopting ANSYS, the process of structural analysis and the manufacturing flow of sensing unit are showed. In dynamic testing conditions, it can be concluded that the axial sensitivity of x, y, and z are Sx = 48 μV/g, Sy = 54 μV/g and Sz = 217 μV/g respectively, and the nonlinearities are 0.4%, 0.6% and 0.4%.

An analytical expression for the impact cross section of rare-earth centres in solids has been deduced. The impact cross sections of four different Er3+ centres in ZnS were calculated. The calculated data are in reasonable agreement with the experimental results. The impact cross sections of different excited states of Ho3+ centres in ZnS were also calculated.

The photoconductivity bands corresponding to the transitions from 6A1 to 4T1, 4T2 and 4E of Mn2+ in ZnSxSe1-x (x=0, 0.01, 0.02, 0.05, 0.10, 0.14) are found. The intensities of these bands relative to that of the intrinsic photoconductivity band are found to vary with x. The configuration model of the manganese centre in ZnSxSe1-x is proposed to explain the experimental results. The positions of the energy levels of Mn2+ in ZnSxSe1-x (x=0-0.10) relative to the conduction band are deduced systematically. The minimum of the configuration curve for 6A1 of Mn2+ is deduced to be 0.44 eV above that of the valence band of ZnSe. The threshold energy for optical excitation from the valence band to ZnSe to the 6A1 state of Mn2+ is found to be 0.69 eV.