This letter reports a novel vector hydrophone based on the piezoresistive effect of resonant tunneling diode (RTD). An external pressure introduces stress in the layers of RTD and induces its current-voltage (I-V) curves change. This effect has been applied to designing new sensor. By control-hole technology, the sensor is processed integrated with GaAs/InxGa1 xAs/AlAs double barrier structures posited on its strain-sensitive region. The fabricated sensor is packaged for watertight solution, and underwater measurements are conducted in RTD's negative differential resistance (NDR) region. Directivity curve of the sensor follows "8" cosine functional form, which shows its vector sound signal detection ability, and its sensitivity reaches 184 6 dB (0dB=1V/Pa) at 1 KHz.

According to the auditory principle of fish’s lateral line organ, a novel microelectromechanical systems (MEMS) bionic vector hydrophone used for obtaining vector information of underwater sound field is introduced in this paper. It is desirable that the application of MEMS-based piezoresistive effect and bionics structure may improve the low-frequency sensitivity of the vector hydrophone as well as its miniaturization. The bionic structure consists of two parts: high-precision four-beam microstructure and rigid plastic cylinder which is fixed at the center of the microstructure. The piezoresistor located at the beam is simulated to the hair cell of lateral line and the rigid plastic cylinder is simulated to stereocilia. When the plastic cylinder is stimulated by sound, the piezoresistor transforms the resultant strain into a differential voltage output signal via the Wheatstone bridge circuit. Microfabrication technology has been employed for the fabrication of the microstructure and measurement results are given. The experiment results show that the receiving sensitivity of the hydrophone is 197.7dB (0dB ¼ 1V/mPa). The novel hydrophone not only possesses satisfactory directional pattern as well as miniature structure, but also has good low-frequency characteristics, and satisfies the requirements for low-frequency acoustic measurement.

This paper reports on the Raman tensor and selection rules of a chemical vapor transport (CVT)-grown CuGaSe2 single crystal. CVT-CuGaSe2 has a hollow needle-like shape with two flat faces of unequal area, (110) and (112), which involve different systems of coordinates. In order to study the Raman spectra of these systems, we probed the theory of Raman tensors and Raman selection rules. Using the MATLAB program, we calculated the Raman tensor of CuGaSe2 (D2d) and other point groups in different orthogonal systems. In addition, by applying the selection rules for Raman scattering to the observation of phonon modes from the (110) and (112) faces of CuGaSe2, we were able to assign the Raman modes at 187, 84 and 68 cm−1, which were in accord with the literature. Additionally, we found some new Raman modes.

This paper reports a novel acoustic sensor with a frequency output based on AlAs/InxGa1−xAs/GaAs resonant tunneling diode (RTD). The RTD is incorporated in a 1um thick membrane and the fabrication technology of the membrane is based upon the selective etch of GaAs with AlAs an etch stop layer. A relaxation oscillator is obtained with the RTD biased in the negative differential resistance (NDR) region. Acoustic pressure applied to the RTD changes the frequency of oscillation due to the shift in current–voltage characteristics. The main feature of this sensor type the direct frequency output, which is linearly dependent on pressure, and the linear sensitivity can be up to 21kHz/kPa.

In this paper, a novel non-dispersive infrared ray (IR) gas detection system is described. Conventional devices typically include several primary components: a broadband source (usually an incandescent filament), a rotating chopper shutter, a narrow-band filter, a sample tube and a detector. But we mainly use the mini-multi-channel detector, electrical modulation means and mini-gas-cell structure. To solve the problems of gas accidents in coal mines, and for family safety that results from using gas, this new IR detection system with integration, miniaturization and non-moving parts has been developed. It is based on the principle that certain gases absorb infrared radiation at specific (and often unique) wavelengths. The infrared detection optics principle used in developing this system is mainly analyzed. The idea of multi-gas detection is introduced and guided through the analysis of the single-gas detection. Through researching the design of cell structure, a cell with integration and miniaturization has been devised. By taking a single-chip microcomputer (SCM) as intelligence handling, the functional block diagram of a gas detection system is designed with the analyzing and devising of its hardware and software system. The way of data transmission on a controller area network (CAN) bus and wireless data transmission mode is explained. This system has reached the technology requirement of lower power consumption, mini-volume, wide measure range, and is able to realize multi-gas detection.

This paper reports a novel GaAs micromachined accelerometer based on the meso-piezoresistive effects of resonant tunneling diodes (RTDs). The sensitive unit of the accelerometer is the RTD which is located at the root of the beams. Based on the meso-piezoresistive effects of RTD, the accelerometer transduces acceleration into electrical signal output. This kind of accelerometer has been fabricated by GaAs IC surface processes and control hole etching technology. The output sensitivity and frequency characteristics of the accelerometer have been tested on the vibrating system. The result indicates that when the RTD is biased in the negative differential resistance region, the sensitivity of the suggested accelerometer is up to 90.51mV/g, and when biased in the positive resistance region, the sensitivity is 2.39 mV/g. It is obvious that the sensitivity in the negative resistance region is more one order higher than that in the positive resistance region, and the sensitivity of the accelerometer can be adjusted through changing the bias voltage. A frequency range of this structure as high as 1.5 KHz has also been achieved.

This letter reports a mesopiezoresistive effect in a double-barrier resonant tunneling (DBRT) structure. In a DBRT system, an external mechanical stress causes a tensile strain, and the strain, in turn, affects the resonant tunneling and thereby the resistance. Theoretical analysis was carried out on an AlAs/GaAs/AlAs DBRT structure under in-plane uniaxial tensile stresses. The results show that the tunneling current and resistance of a DBRT structure change significantly with external stress-induced tensile strains. The results also show that the resistance-strain response can be tuned effectively by the external voltage. The effect has potential applications in miniature electromechanical devices.