ABSTRACT
This paper explores poly-silicon-germanium (poly-SiGe) avalanche photo-sensors (APSs) involving a device of heterojunction structures. A low pressure chemical vapor deposition (LPCVD) technique was used to deposit epitaxial poly-SiGe thin films. The thin films were subjected to annealing after the deposition. Our research shows that the most optimal thin films can be obtained at 800 °C for 30 min annealing in the hydrogen atmosphere. Under a 3-µW/cm2 incident light (with a wavelength of 550 nm) and up to 27-V biased voltage, the APS with a n+-n-p-p+ alloy/SiO2/Si-substrate structure using the better annealed poly-SiGe film process showed improved performance by nearly 70%, 96% in responsivity, and 85% in quantum efficiency, when compared to the non-annealed APS. The optimal avalanche multiplication factor curve of the APS developed under the exponent of n = 3 condition can be improved with an increase in uniformity corresponding to the APS-junction voltage. This finding is promising and can be adopted in future photo-sensing and optical communication applications.
ABSTRACT
Diamond-incorporated copper metal matrix layers were fabricated on brass substrates by using electrodeposition technology in this study. To improve the adhesion of the composite coatings on the brass substrate, a plated copper was applied as the interlayer between the multilayers and the substrate. The surface morphologies of the interlayer and the diamond-incorporated copper composite layers were studied by scanning electron microscopy. The effect of the copper interlayer on the incorporation and the distribution of the diamond content in the coatings was analyzed by surface roughness, electrochemical impedance spectroscopy, and cyclic voltammetry. The diamond content of the composite coating was measured by energy-dispersive X-ray. The film thickness was evaluated by the cross-sectional technique of focused ion beam microscopy. The element, composition, and crystallization direction of diamond with Cu matrix was measured by X-ray diffraction and transmission electron microscope. The adhesion of the multilayers was studied by scratch tests. The experiment results indicated that the diamond content and distribution of the coating were higher and more uniform with the Cu interlayer than that without one. The plated copper interlayer reduced the electrical double-layer impedance and enhanced the adsorption of diamond particles by the surrounding Cu ions, which promoted the diamond content in the composite coatings. The roughened surface caused by the plated Cu interlayer also improved the substrate's mechanical interlock with the composite coating, which contributed to the strong adhesion between them.
ABSTRACT
PURPOSE: This study compared the performance of a newly patented synchronized valve (SV) with that of a commercially available (CAV) bileaflet mechanical heart valve. DESCRIPTION: A high-speed camera was used to record the leaflet kinematics of the SV vs the CAV along the flow channel. Transvalvular energy loss, effective orifice area, and hemolysis ratios were obtained using a mock circulatory system at two fixed pulse rates and at various cardiac outputs with a fixed aortic pressure. EVALUATION: The rotational radius and inertia of the SV was lower than that of the CAV during valve closure. For heart rates and at cardiac outputs of 7, 5, and 4 L/min, the ratio of total energy loss to effective energy of the SV was significantly less than the CAV, whereas the effective orifice area of the SV was significantly larger than that of CAV. The hemolysis ratio after 4 hours was significantly higher in the CAV than in the SV for both pulse rates. CONCLUSIONS: The synchronized leaflet motion mitigated leaflet rebound and regurgitation during valve closure, which could decrease energy loss, increase the effective orifice area, and reduce hemolysis.
