Field of Expertise: Advanced Material Science
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Field of Expertise: Advanced Material Science | |
Variable tunnelling barriers between isolated nanosized metal grains as key element for a new sensor concept The development of simple gas sensing concepts is still of great interest for science and technology. Ideally, a sensing device would be fabricated in a single-step procedure, providing sensitive, analyte-selective, quantitative and reversible performance characteristic without the requirement of special operating conditions or reformation cycles by means of high temperatures and / or special environments after a detection event. We demonstrate a new gas sensing concept based on a Pt-C metal-matrix system which is fabricated in a single-step by focused electron beam induced deposition (FEBID). The obtained sensing devices react selectively on polar H2O molecules in a quantitative and reversible manner without any formation or reformation cycles while exposure to non-polar species (O2, CO2, N2) produces no response. The key elements are isolated Pt nano-grains (2–3 nm) which are homogeneously distributed in a dielectric carbon matrix. Charge transport in such material systems is based on tunnelling events in the correlated variable range hopping regime, where the dielectric carbon matrix screens the applied electric field between adjacent particles, which governs the final conductivity of the device. The specific change of these dielectric properties through physisorption of polar gas molecules (like H2O) on the device surface can change the tunnelling probability and thus the overall conductivity, allowing their application as a simple and straightforward sensing concept. The study is completed by theoretical considerations and related calculations are in good agreement with experimental observations. Together with the high flexibility of FEBID based processing techniques the presented sensor concept represents the starting point for special tailored sensor applications. |