ИСТИНА

Using of gas sensors based on OFETs are promising solution due to a wide range of fabrication methods, a variety of materials for layers creation and the possibility to customize the device architecture. To reach highly sensitive performance it is necessary to understand how to select functional layer materials and to choose manufacturing method of the such layers for correctly. In this work we consider sequentially each of the active functional layers of the OFET gas sensors and formulate recommendation for their fabrication. It obvious that semiconductor layer plays a key role, since the charge transport changes occur in that, which causes the sensory response appearance. To achieve ultra-high sensitivity OFET gas sensors it is necessary to predominantly use monolayer devices that provide direct contact of the target gas with the current-carrying layer. The appropriate technology monolayers fabrication is the Langmuir-Schaefer method. The LS method is compatible with roll-to-roll technologies, doesn’t require expensive equipment, and an organic solvent absence in the formed film significantly expands the range of materials suitable for underlying layers creation. Thus, in addition to thermal-oxidative stability, materials must be capable to self-assembly. Metalloporphyrins are an excellent base for the receptor layers formation due to the presence of various coordination metal ions in their structure. The LS method is a suitable method for receptor layers formation, because it allows to fabricate thin films which cover a semiconductor without disturbing its structure. Receptors selection should be based on the principle of minimal correlations between the responses of the sensors included in the “electronic nose” to the target analyte gases1. Thin layers based on octyldimethylchlorosilane (ODMS), polymethyl methacrylate (PMMA), polystyrene (PS) and fluorinated polymer (CYTOP) deposited on silicon substrates by any of the solution methods (Spin Coating, Dr. Blade) can be used as interface dielectrics. It has been shown that OFETs based on ODMS demonstrated the highest sensitivity, OFETs based on PMMA shown the longest lifetime and electrical properties stability during long-term measurements, and OFETs based on CYTOP have the minimum threshold voltage, allowing operation at low operating voltages. Printed additive technologies permit to create cheap and/or disposable devices. Understanding the principles of the additive functional layers formation allows to manufacture printed sensors, in particular capacitive gas sensors2. Using of the printed capacitive sensors (PCS) in combination with OFET gas sensors makes possible to significantly expand the range of measured ammonia ana toluene concentrations: from concentrations comparable to the TLV of residential areas to concentrations requiring immediate evacuation.