Ultralow drift in organic thin-film transistor chemical sensors by pulsed gating

A pulsed gating method has been developed to enhance the baseline stability of organic thin-film transistor (OTFT) chemical sensors. Trap states in the organic films are the major source of the OTFTs baseline drift under static gate bias, which is identified as the bias stress effect (BSE). BSE typically reduces the baseline current by 60% over 20 h in phthalocyanine based OTFT sensors. The baseline drift has been reduced below 1% over 20 h in the absence of the analyte using the pulsed gating method. With pulsed gating, the baseline drift on exposure to 15 methanol pulses is less than 0.09% /h, and the response to this analyte is fully recoverable. Similar ultralow drift results were obtained for methanol sensing on three different phthalocyanine OTFTs. Combining the pulsed gating with low duty cycle analyte pulses, this method is also applicable to obtain ultralow drift (0.04%/h) even for low vapor pressure analytes such as organophosphonate nerve agent simulants. (c) 2007 American Institute of Physics.