The temperature-dependent ammonia gas sensing performance of an interesting indium tin oxide (ITO) based device with an underlying Au-nanodot layer (ITO-Au) is studied and demonstrated. The studied ITO-Au device exhibits good ammonia gas sensing performance and widespread ammonia gas concentration regime. The optimal operation temperature of the studied ITO-Au device is 150 degrees C. The studied ITO-Au device exhibits the benefit of improved sensing performance and extremely low ammonia gas concentration detecting ability. For example, under introduced 1000 ppm and 175 ppb NH3/air gases, the studied ITO-Au device demonstrates remarkable sensitivity ratios of 1786% and 98%, respectively, at 150 degrees C. The related transient responses are also studied. The enhanced sensing performance of the studied ITO-Au device is primarily caused by the presented rougher surface which gives to the increased effective adsorption area. Experimentally, the studied ITO-Au device reveals advantages of simple structure, ease of fabrication, high sensing response, extremely low ammonia gas detecting limit, and low temperature operation capability. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.072302jes] All rights reserved.