Volume 96, Issue 2, 15 July 2004
Index of content:
- INTERDISCIPLINARY AND GENERAL PHYSICS (PACS 1-41, 43-47, 79, 81-84, 89-99)
Ge composition dependence of properties of solar cells based on multicrystalline SiGe with microscopic compositional distribution96(2004); http://dx.doi.org/10.1063/1.1763227View Description Hide Description
We present device performance of solar cells based on multicrystalline SiGe (mc-SiGe) bulk crystal with microscopic compositional distribution grown by the casting method. The average Ge composition was systematically changed in the range between 0% and 10%. A small addition of Ge to multicrystalline Si (mc-Si) was found to be very effective to increase the short-circuit current density without affecting the open-circuit voltage. As a consequence, the overall efficiency of a solar cell based on mc-SiGe was improved compared with that based on mc-Si. This result demonstrates that mc-SiGe is a promising candidate to replace mc-Si since it could achieve higher conversion efficiency without drastic increase of the production cost.
Ultrasonic enrichment of microspheres for ultrasensitive biomedical analysis in confocal laser-scanning fluorescence detection96(2004); http://dx.doi.org/10.1063/1.1763226View Description Hide Description
An ultrasonic particle concentrator based on a standing-wave hemispherical resonator is combined with confocal laser-scanning fluorescence detection. The goal is to perform ultrasensitive biomedical analysis by concentration of biologically active microspheres. The standing-wave resonator consists of a 4 MHz focusing ultrasonic transducer combined with the optically transparent plastic bottom of a disposable 96-well microplate platform. The ultrasonic particle concentrator collects suspended microspheres into dense, single-layer aggregates at well-defined positions in the sample vessel of the microplate, and the fluorescence from the aggregates is detected by the confocal laser-scanning system. The biochemical properties of the system are investigated using a microsphere-based human thyroid stimulating hormoneassay.
96(2004); http://dx.doi.org/10.1063/1.1759400View Description Hide Description
The paper describes experiments on the generation and transport of a low energy (70–120 keV), high intensity (10–30 microsecond duration ion beam (IB) in vacuum and plasma. The IB was generated in a magnetically insulated diode (MID) with an applied radial B field and an active hydrogen-puff ion source. The annular IB, with an initial density of at the anode surface, was ballistically focused to a current density in the focal plane of 50–80 The postcathode collimation and transport of the converging IB were provided by the combination of a “concave” toroidal magnetic lens followed by a straight transport solenoid section. With optimized MID parameters and magnetic fields in the lens/solenoid system, the overall efficiency of IB transport at the exit of the solenoid 1 m from the anode was ∼ 50% with an IB current density of 20 Two-dimensional computer simulations of post-MID IB transport supported the optimization of system parameters.
Simple analytical approximations for eddy current profiling of the near-surface residual stress in shot-peened metals96(2004); http://dx.doi.org/10.1063/1.1762708View Description Hide Description
Because of their frequency-dependent penetration depth, eddycurrentmeasurements are capable of mapping the near-surface depth profile of the electrical conductivity. This technique can be used to nondestructively characterize the subsurface residual stress distribution in certain types of shot-peened metals, e.g., in nickel-base superalloys. For quantitative evaluation of the experimental results, analytical and computational techniques are needed to solve the direct and inverse problems, i.e., to predict the frequency-dependent apparent eddycurrent conductivity from the depth profile of the frequency-independent intrinsic electrical conductivity of the specimen and vice versa. Simple analytical approximations are presented for both the direct and inverse eddycurrent problems by exploiting two specific features of the subsurface electrical conductivity variation caused by near-surface residual stresses in shot-peened metals. First, compressive residual stresses are limited to a shallow surface region of depth, much less than typical probe coil diameters. Second, the change in electrical conductivity due to residual stresses is always very small, typically less than 1%. The proposed approximations are verified by numerical comparison to much more complicated numerical solutions.