Effects of heat treatment on Ta2O5 sensing membrane for low drift and high sensitivity pH-ISFET

This paper presents a new approach for reducing the drift and improving the sensitivity of a pH-ISFET by varying the heat treatment condition of the Ta 2 O 5 sensing membrane. A Ta 2 O 5 pH-ISFET which was heat-treated at various temperatures, showed very different sensing characteristics such as sensitivity, long-term drift, etc. When heat-treated in O 2 ambient at 400°C for I h, Ta 2 O 5 pH-ISFET showed low drift, which is maybe related to a densification effect of the film in an amorphous state with a low leakage current. Furthermore, the Ta 2 O 5 pH-ISFET which was heat-treated in O 2 , showed good sensitivity, which is maybe associated with an increase of O-sites at the surface. The Ta 2 O 5 pH-ISFET fabricated by the above method showed good linearity, high sensitivity (58-59 mV) over a wide pH range (pH 2-12) and low long-term drift (0.03-0.05 pH/day).

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