Hydrogen sensing properties of dielectrophoretically assembledSnO2 nanoparticles on CMOS-compatible micro-hotplates

Abstract

We fabricated nanoparticle-based gas through in situ ac dielectrophoretical assembling of drop-coatedSnO2 nanoparticles to bridge the gap between electrodes with high aspect ratio.While the conventional dielectrophoresis (DEP) adopts a microfluidic systemfor continuous flow of the solution during the process, we just drop-coated asmall amount of solution onto the electrodes and executed in situ DEP for avery short time. This is a very simple, cost-effective, time-saving, and highlyreproducible process. We fixed the duration time and applied voltage for the DEPat 1 s and 1 V respectively and changed the frequencies from 1 up to 500 kHz.I–V characteristics of the samples were checked and it was found that DEP samples fabricated at1 s, 1 V and 150 kHz conditions showed considerably higher connectivity of the nanoparticles.This can be attributed to the excellent step coverage achieved by ac DEP under thoseconditions. The devices drop-coated and dielectrophoretically assembled at other ac frequencyconditions showed poor connectivity. Hydrogen gas sensing properties of the sensorsfabricated under 1 s, 1 V and 150 kHz conditions were checked by flowing through 160 ppmH2. The sensitivity reaches a maximum value of ∼ 700% at350 °C. The responsetime is ∼ 200 s at 350 °C.