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Photoluminescence measurements and high-resolution transmission electron microscopy studies on spark-treated (porous) silicon have been performed. Contrary to suggestions put forward by others, it has been found that spark erosion does not yield structures comparable to those obtained for irradiated, that is, damaged silica. Instead, evidence is given that spark treatment of single crystalline silicon wafers produces randomly oriented nanometer-sized silicon crystallites surrounded by a SiO2 matrix. This configuration is believed to be responsible for the observed room temperature visible photoluminescence.

Abstract-This paper discusses the use of printed circuit board (PCB) integrated inductors for low power dc/dc buck converters. Coreless, magnetic plates and closed core structures are compared in terms of achievable inductance, power handling and efficiency in a footprint of 10 10 mm 2 . The magnetic layers consist of electroplated NiFe, so that the process is fully compatible with standard PCB process. Analytic and finite element method (FEM) methods are applied to predict inductor performance for typical current waveforms encountered in a buck converter. Conventional magnetic design procedures are applied to define optimum winding and core structures for typical inductor specifications. A 4.7 H PCB integrated inductor with dc current handling of up to 500 mA is presented. This inductor is employed in a 1.5 W buck converter using a commercial control integrated circuit (IC). The footprint of the entire converter measures 10 10 mm 2 and is built on top of the integrated inductor to demonstrate the concept of integrated passives in power electronic circuits to achieve ultra flat and compact converter solutions.

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