Temperature controlled phase transition as a detection principle for gas FETs (TPT-FET)

A new hydrogen sensor based on a heterogeneous polymer-platinum layer is presented. The sensor is based on the well-known floating gate field effect transistor (FG-FET [1]), which is shown in fig. 1. This type of sensor is capable of detecting various gas species [1,2,3] by measuring the work function change of a well chosen sensitive layer on which the target gas molecules are adsorbed. In the past platinum [1] or palladium [4] films as well as some heterogeneous metal oxide - platinum layers [5] have been used as sensitive materials for hydrogen detection. The main insufficiency of all these sensors is the low upper detection limit of about 2 % of hydrogen and the instabilities of the baseline in combination with its analogous detection behavior. To overcome these deficits we developed a new heterogeneous polymer - platinum system acting as sensitive layer. Using this new combination of materials, the FG-FET response to different concentrations is proportional only below a certain limit. Above this limit, the signal immediately steps to a maximum value. As this switching point is tunable, a new operation mode was developed, allowing precise hydrogen concentration measurements up to concentrations of at least 4 %.