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High-quality monolithic Ge-on-Si is sought for CMOS-compatible optoelectronic devices. We examine the structural characteristics of Ge-on-Si grown by the aspect ratio trapping (ART) method on a SiO2/Si(001) template in pre-patterned holes. Transmission electron microscopy and surface topography analysis revealed high-quality Ge islands overgrown from the ART holes in SiO2. The superior crystal quality of Ge ART growth was also confirmed by comparing x-ray diffraction (XRD) data of Ge ART and Ge planar epilayer samples. The XRD and micro-Raman data additionally show a small residual strain in the islands which vanishes by reducing the hole diameter from 280 nm to 180 nm, while leading to only a minor increase in the crystallographic inclinations of the Ge islands from 0.34 deg to 0.54 deg. With finite element method simulations, we find that the small residual strain in Ge originates during the cool-down from growth to room temperature because of thermal expansion coefficient mismatch between Ge and SiO2. A tensile force develops along the [001] axis of the Ge pillar whose faster shrinkage to the room temperature volume is restricted by the oversized surface island. [ABSTRACT FROM AUTHOR]

We propose a time-of-flight ranging method by measuring the pulse laser phase based on field-programmable gate array (FPGA) digital mixing, in which accurate laser ranging with a total digital system is realized by combining one FPGA chip with a simple laser transmitting and receiving circuit. The system has the advantage of simple structure, reliable operation, low manufacturing cost and easy integration. Experimental results show that compared with the pulse laser ranging method using commercial time-to-digital converter chips, it can realize precise measurement of distance, and the measurement error can be significantly reduced. In addition, this method has better performance of ranging accuracy. [ABSTRACT FROM AUTHOR]

Manganese dioxide exhibits the ideal capacitive behavior in aqueous electrolytes containing alkaline-earth cations (Mg[sup2+], Ca[sup2+] or Ba[sup2+]). A specific capacitance value as high as 325 F g[sup-1] was obtained in 0.1 mol L[sup-1] Mg(NO[sub3])[sub2] electrolyte at 2 mV s[sup-1]. The ideal capacitive behavior, high specific capacitance, good coulombic efficiency, and rate ability of manganese dioxides in aqueous electrolytes containing bivalent cations (Mg[sup2+], Ca[sup2+], or Ba[sup2+]) indicate that these alkaline-earth cations might be good alternatives for the state-of-the-art univalent alkaline cations. Moreover, activated carbon/MnO[sub2] asymmetric capacitors with 2 V operating voltage were built up based on the aqueous electrolytes containing these alkaline-earth cations. The energy density of the AC/MnO[sub2] asymmetric capacitor with Ca[sup2+] cation at a current density of 0.3 A g[sup-1] was found to be 21 Wh Kg[sup-1]. [ABSTRACT FROM AUTHOR]