Investigation on a sensitive Au thin film deposited on different substrates: Physical analysis via FIB and chemical analysis via evaluation of Au sensitivity to Hg0

Recent advances in micro system technology (MST) require special materials – generally deposited in a thin film form – to allow detection of specific (bio)chemicals and to provide appropriate functionality. The rapid expansion of materials available to thin-film designers addresses a clear need of design issues at the micro and nano scale.In this paper the properties of a sensitive gold (Au) thin film deposited on different substrates are investigated.The use of focused ion bean (FIB) technique – which combines milling capability with in situ nanometric resolution imaging – as a powerful tool for thin film inspection is demonstrated.Thin film sensitive behaviour is experimentally evaluated as sensitivity to elementary gaseous mercury (Hg0). Experimental data are collected by using the experimental set-up developed by the authors in a previous work and analysed by using the mathematical model developed and described in the same paper. A clear change in Hg0 sensitivity of Au thin films deposited on different substrates is observed. Based on FIB and chemical analysis, the authors conclude that the substrate does not influence Au thin film intrinsic properties. A generalisation of the mathematical model is provided by introducing a contribution arising from the roughness of the substrate to the change in Hg0 sensitivity, thus allowing the interpretation of the experimental results.