The phosphosilicate glass (PSG), fabricated by tube furnace diffusion using a POCl 3 source, is widely used as a dopant source in the manufacturing of crystalline silicon solar cells. Although it has been a widely addressed research topic for a long time, there is still lack of a comprehensive understanding of aspects such as the growth, the chemical composition, possible phosphorus depletion, the resulting in-diffused phosphorus profiles, the gettering behavior in silicon, and finally the metal-contact formation. This paper addresses these different aspects simultaneously to further optimize process conditions for photovoltaic applications. To do so, a wide range of experimental data is used and combined with device and process simulations, leading to a more comprehensive interpretation. The results show that slight changes in the PSG process conditions can produce high-quality emitters. It is predicted that PSG processes at 860 C for 60 min in combination with an etch-back and laser doping from PSG layer results in high-quality emitters with a peak dopant density N peak ¼ 8.0 Â 10 18 cm À3 and a junction depth d j ¼ 0.4 lm, resulting in a sheet resistivity q sh ¼ 380 X/sq and a saturation current-density J 0 below 10 fA/cm 2 . With these properties, the POCl 3 process can compete with ion implantation or doped oxide approaches. Published by AIP Publishing. [http://dx.
We propose and demonstrate a coherent laser-plasma point x-ray source in the water window spectral region operating at a repetition rate of up to 100 Hz. The emission from the 10-μm-diameter source is filtered to generate monochromatic radiation at a 3.37 nm wavelength. Soft x-ray fringes of the Young’s interference experiment were obtained with a visibility of 0.62±0.1 with a slit pair of 10.5 μm separation at a distance of 31.7 cm from the source. The source can be used to take either a hologram or transmission scanning x-ray micrograph within a reasonable exposure time of several minutes.
In order to allow widespread application of soft X-ray lasers there is a strong effort worldwide to use as small as possible pump lasers for plasma production. Short pulse lasers (-c~ 1 ps), particularly in the UV, have attracted much interest, since extremely high intensities (up to 10 ~8 W/cm 2) can be achieved with a relatively high repetition rate. In this article we discuss their merit for soft X-ray laser pumping and possible solutions to the specific problems, for instance pulse front distortion, nonlinear absorption in window materials, plasma formation by short laser pulses and the relatively low total pump energy.
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