lithographic processing for nanopatterned gas sensors
Additive process. Electron beam lithography and lift-off technique are employed for fabrication of a nickel pattern (steps 1–5); the Ni mask is transferred to underlying by means of reactive ion etching (step 6); after removing nickel (step 7), patterned is used as substrate for the deposition of separated wires.
(a) Vertical sidewalls of -thick structures after removal of Ni mask; (b) same structures after tin deposition: material on top of structures is separated from that at the bottom.
Typical result of the additive process reported in Fig. 1: high resolution wires are produced.
based reactive ion etching process for : (a) etch rate as a function of concentration; (b) effects of Ar addition for fixed to ratio (0.4). As shown, a clear maximum is observed for 40% of concentration (a); moreover, addition of small Ar amounts can improve the etch rate (b). Reported lines are only a guide for eyes.
Patterned sensor device completed with circuitry elements: the pattern is in the middle of the sample, whereas all around are visible the heater element and parallel contacts for wires. The inset shows the sensor bonded to a TO-8 case, ready for measurements.
Functional characterization of wire sensor (solid line) and continuous film sensor (dashed line). For all testing gases, responses from patterned sensor are higher than those from continuous film sensor.
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