Key Engineering Materials Vols. 645-646

Abstract: As a nanoelectronic system, Quantum-dot cellular automata (QCA) is very likely to present high defect and fault rates. Therefore making QCA bits distortion-free is a necessary work. In this paper, we present the QCA based rate-1/2 and memory length-2 convolutional encoders that can generate one kind of error correcting codes from the perspective of information redundancy. Three schemes of layouts are presented and compared, and the majority-based type has the compactest layout and lowest latency. Our simulation results demonstrate that these encoders can all functionally work.

Abstract: We have theoretically and experimentally investigated the microcavity organic light-emitting diodes (MOLEDs) that enhanced the emission intensity and narrowed the spectra simultaneously. In this work, MOLEDs with the reflectivities of 70% and 90% have been successfully fabricated. Comparing to non-cavity OLEDs, the maximum forward electroluminescence intensity and the peak luminescence can be improved by 6.8 times and 2.2 times, respectively. The full width at half maximum could be sharply narrowed to 10 nm. The different configurations of MOLEDs with varied emitting layers have also been evaluated which fitted well with the experimental results.

Abstract: AZ 1518 is a standard thin positive photoresist in AZ1500series which has been widely used in photolithography process, beside this, as a perfect semiconductor material, micro sized silicon cantilevers have been widely used in micro electromechanical systems (MEMS). In This paper, we have presented the process of fabricate micro silicon cantilever, including the selection of the photoresist, developer and substrate, optical lithography method and PLD method. After these, AFM is used to study the cantilever pattern and the angle of inclined planes. The research results show the exposure time and experimental environment can significantly influent the quality of cantilever pattern.

Abstract: A laser ranging system for scanning detection based on phase shift ranging technology and a MEMS mirror for space detection and measurement is presented in this paper. The laser ranging system is mainly composed of a modulation module, a laser, a MEMS mirror, a photo-electric conversion module and a signal processing module. The phase shift ranging method is used to measure the relative range to the target. The MEMS mirror is a micro scanner with two DOF, which is used to change the direction of the emitted laser beam. The modulated laser beam is emitted through the MEMS mirror and reflected from the target. The relative range is calculated by the phase shift between the emitted beam and the reflected beam. The experimental results indicate that the measurement accuracy is 0.10 m in static status and 0.17 m in scanning status in the range of 3 m. The differences between the static and the scanning status are analyzed and improvements are proposed.

Abstract: In this paper, the working mechanism and high characteristics of an InP/InGaAsP uni-traveling-carrier (UTC) double hetero-junction phototransistor (DHPT) has been analyzed. The UTC-DHPT employs a heavy doping base and two hetero-junctions to realize UTC structure to ease the contract between HPT responsivity and HPT working speed. Optical responsivity and optical transit frequency are analyzed physically through illustrated several kinds of paramistic capacitors in BE junction and BC junction under different electrical bias, optical bias and combined electrical and optical bias in this work. The results show that three-terminal (3T) working mode with combined electrical bias and optical bias in base achieves a highest maxim f_T of 120GHz at collector current of 30mA and keeps the same optical responsivity (37.5A/W) compared with two-terminal (2T) working mode.

Abstract: Many gas molecules absorb electromagnetic radiation at characteristic wavelengths in the infrared region. This absorption can be used to identify defined substances like CO2, ammoniac, and so far. This study presents a comparative analysis of parameters of infrared radiation source and detector hardware that are most important for the creation of portable optical nondispersive infrared (NDIR) gas sensors. One of the central issues in the design of this kind of sensors is the geometry of the sensor cell. In this paper we investigate an asymmetry sensor cavity and predict the performance using Tracepro software. Then, the CO2 sensor is made and tested.

Abstract: A micromirror fabricated by surface micromachined process is developed. The developed micromirror contains four pre-stress comb-drive actuators, which support tip/tilt/piston degrees of freedom. Pre-stress comb-drive actuators have the advantage of large displacement and fast response. Prototype is fabricated by a commercially available MEMS surface micromachined process. Experimental results indicate that the device can realize designed function and have the potential in MOEMS applications.

Abstract: A 3D shape measurement system based on a laser rangefinder and a two-dimensional MEMS mirror is presented in this paper. According to the requirement of surface profile measurement, the 3D shape measurement system is mainly composed of a laser module, a two-dimensional MEMS mirror, a ranging module, an orientation module and an image composition module. Based on the MEMS scanning technology and phase shift ranging method, the surface profile of the target can be acquired by the measurement system. For the coupled scanning mode, the scanning pattern is simulated in Lissajous figure and the condition of covering all the field of view is analyzed. The simulation results show that the 3D shape measurement system based on the laser rangefinder and the two-dimensional MEMS mirror can realize the measurement the surface profile of the target in all the field of view.

Abstract: This paper presents the design of an interface circuit for storing power generated by low-frequency vibration based electrostatic energy harvesters. The circuit includes a structure of negative voltage converter with an active diode to minimize the forward voltage drop, and it also includes a boost-buck converter to accommodate a wide input voltage. The circuit has also been optimized to perform resistive matching. The maximum voltage of the capacitor in charging reaches about 1.83 V in simulation.

Abstract: Aluminum nitride (AlN) film as a piezoelectric material has been used widely, particularly in vibration energy harvester due to its unique and enhanced properties such as high temperature resistance and compatibility with CMOS processes. In this work, AlN film with (002) preferred orientation was prepared on silicon wafers by pulse DC reactive magnetron sputtering (RMS), and the properties such as peak intensity, full width at half maximum (FWHM) and surface morphology were investigated by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The preferred orientation was found to be sensitive to deposition conditions such as gas flow rate, power, bottom electrodes materials and substrates temperature. The results shows that the intensity was 1.1×10⁵ counts, the FWHM was 1.9owhen the temperature was 260°C. The film was used to fabricate the vibrated energy harvester successful and the power density reached about 3000uW/cm³ at the vibration frequency under 1g acceleration.