The morphology of metal‐assisted electroless etched n‐type silicon in HF–oxidizing agent–H2O etching system as a function of oxidizing type and etching time was studied. Three types of oxidizing agent were investigated: Na2S2O8, K2Cr2O7 and KMnO4. The layers formed on silicon were investigated by scanning electron microscopy and energy‐dispersive X‐ray analysis. It is shown that the morphology of the etched layers depends strongly on the type of oxidizing agent. The secondary ion mass spectra of the etched layers reveal that the deposited silver diffuses into the etched layers during etching. Finally, a discussion on the dissolution mechanism of silicon by silver‐assisted electroless etching is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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In the present work, pure BiFeO3 (BFO) particles were synthesized by sol-gel method and mixed with carbon fibre to form composites (x%CFs-BFO, where x corresponds to 0, 4, 8 and 10 wt.%) by hydrothermal treatment at 150?C. The resulting composite powders were characterized by X-ray diffraction, Raman spectroscopy, nitrogen adsorption/desorption isotherm and scanning electron microscopy (SEM-EDX). The synthesized powders were used for gas sensors preparation by manual deposition of their mixture with polyvinyl alcohol on alumina tubes ending with two silver electrodes. The impedance of the sensitive layers was determined by impedance spectroscopy in the temperature range 100-250?C at different gaseous concentrations. The detection properties of the fabricated sensors for various volatile organic compounds were investigated. The sensors showed better sensitivity to acetone compared to other gases. The addition of carbon fibres improved the sensitivity to acetone vapour from 64 to 135% at 100 ppm and reduced the optimum operating temperature of the sensors by 20?C and the response and recovery times from (26 s/15 s) to (18 s/10 s). This study revealed that x%CFs-BiFeO3 composites are promising candidates for gas sensors.