<title>Micromechanical structure development for chemical analysis: study of porous silicon as an adsorbent</title>

Abstract

The aim of this work is to investigate the use of microchannels to concentrate pollutants present in the air. Devices with a length of 30 cm, a width of 100 tm and a depth of 30 tim, sealed by anodically bonded glass, were manufactured. Tests of adsorption characteristics were made using n-hexane. To reliably insert N2 contaminated with 1000 ppm of n-hexane in the microstructure, a simple setup was manufactured. This setup allows to insert the reactant, remove the amount of reactant adsorbed and to detect it. An amount of 20 mg was inserted in the microstructure. In order to improve the adsorption characteristics, PS (porous silicon) layers were manufactured in the microchannels using silicon nitride as mask. The sealing of the microstructure with anodic bonded glass showed to be feasible either if the surface presents PS or silicon nitride. Samples of PS layers covered by a plasma polymerized film, produced using HMDS, were analyzed by Raman microscopy. It was noticed that the nanocrystals are completely fulfilled by the deposited material, indicating the high reactivity of the PS layer.

Polymer Production by Plasma Polymerization of Oxygenated Organic Compounds

“…Depositions were performed with grounded or powered auxiliary gas system. Positive bias was responsible for the most important changes in the plasma [1] . The maximum voltage used was 80.0 V due to the high instability of the plasma conditions when higher voltages are used.…”

“…These new films are usually required in Micro Electro Mechanical Structures (MEMS) for production of micro devices. For instance, devices based on micro channels can adsorb hydrocarbons from the air, an ability that may be used for environmental analysis [1] . Up to now, these devices are able only to concentrate non-polar compounds in a gaseous matrix.…”