Semiconductor Device-Based Sensors for Gas, Chemical, and Biomedical Applications

ZnO Thin-Film and Nanowire-Based Sensor Applications 159

© 2011 by Taylor & Francis Group, LLC

AES depth proles of the Ti/Al/Pt/Au contact after annealing at 200°C showed that the initially

sharp interfaces between the different metals are degraded by reactions, especially between the Ti

and the ZnO to form Ti-O phases

29,30

and between the Pt and Al. We found that anneals at 600°C

almost completely intermixed the contact metallurgy. Low thermal stability of both ohmic and

Schottky contacts on ZnO appears to be a signicant problem in this materials system, and clearly

there is a need to investigate refractory metals with better thermal ...