We report the parallel fabrication of miniaturized chemical sensors by the direct integration of nanostructured transition metal oxide films onto micro-hotplate platforms based on micromachined suspended membranes. This has been achieved by local deposition on a 10 × 10 membrane wafer of a supersonic cluster beam through a microfabricated auto-aligning silicon shadow mask. The sensing properties of the obtained devices were tested with respect to various gaseous species. For reducing and oxidizing species such as ethanol and NO 2 , very good performance in terms of linearity and sensitivity was observed. These results demonstrate the feasibility of the coupling of a bottom-up nanofabrication technique such as supersonic cluster beam deposition to a top-down microfabricated platform for a direct and parallel integration methodology of nanomaterials in MEMS.
Cluster-assembled nanostructured films of refractory metal oxides were produced by supersonic cluster beam deposition (SCBD) using a pulsed microplasma cluster source (PMCS). The growth of nanostructured films takes place at room temperature on substrates exposed to nanoparticles beam. Soft landing and limited diffusion are peculiar characteristics of the deposition process, causing the film to grow according to a highly porous structure. We produced nanostructured Mo, W, and Nb oxide films and we characterized their crystal structure and film morphology at the nanoscale together with their gas sensing performances. The effect of thermal treatments on grain growth and morphology modification was particularly addressed in view of the use of the nanostructured layers in gas sensing applications on microfabricated platforms.
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