Electrical and topological characterization of thin film transistors based on a novel organic semiconductor for biosensing applications

Abstract

The design of sensors capable of detecting various analytes has important biosensing applications ranging from medical diagnostics to air quality monitoring. Organic-based semiconductors are being promoted as biosensors for their cost-effectiveness, facility of fabrication and potential for reaction to many analytes. This study aims to characterize the electrical performance and topology of thin film transistors (TFTs) based on a novel semiconducting molecule with a conjugated phenyl-thiophene core, 5-5'-bis-4-(6-hydroxyhexyloxy)-phenyl-2-2'-bithiophene (or HOC6PTTPC6OH for short). Electrical measurements show that working TFTs can be fabricated from this novel material and exhibit consistent transistor performance. Atomic Force Microscopy reveals a polycrystalline structure with distinct grains separated by crevices, the degree of which depends on the deposition process. The electrical performance (measured by the field effect mobility) is shown to depend on the topology, and therefore on the details of film deposition. Based on these findings, possible improvements to the fabrication method to optimize electrical performance and sensing response are discussed with relation to future studies on these devices as alcohol vapor sensors, and potentially, as DNA sensors.