Abstract
The use of metal nanoparticles as seed layers forcontrolling the microstructures of tin oxide (SnO2) filmson temperature controllable micromachined platforms has beeninvestigated. The study is focused on SnO2 due to itsimportance in the field of chemical microsensors. Nanoparticleseeds of iron, cobalt, nickel, copper and silver were formed by vapour deposition on the microhotplates followed by annealing at 500 °C prior to self-aligned SnO2 deposition.Significant control of SnO2 grain sizes, ranging between20 and 121 nm, was achieved depending on the seed-layer type. Acorrelation was found between decreasing the SnO2 grain sizeand increasing the melting temperature of the seed-layer metals,suggesting the use of high temperature metals as being appropriate choices as seed layers for obtaining a smaller SnO2 grainstructure. Smaller grain diameters resulted in high sensitivityin 90 ppm ethanol illustrating the benefits of nanoparticleseeding for chemical sensing. The initial morphology, particlesize and distribution of the seed layers was found to dictatethe final SnO2 morphology and grain size. This papernot only demonstrates the possibility of depositingnanostructured oxide materials for chemical microsensorapplications, but also demonstrates the feasibility ofconducting combinatorial research into nanoparticle growthusing temperature controllable microhotplate platforms. Thispaper also demonstrates the possibility of usingmulti-element arrays to form a range of different types ofdevices that could be used with suitable olfactory signalprocessing techniques in order to identify a variety of gases.
Published Version
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