A Study of Organic Field-Effect Transistors with Bovine Serum Albumin as Gate Dielectric

• Main Author: 李雋毅
• Other Authors: 黃振昌
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/77278201695363885122

博士 === 國立清華大學 === 材料科學工程學系 === 103 === Bovine serum albumin (BSA) is a natural protein with good hydration ability which contains acidic and basic amino acid residues of ca. 34% in total. In vacuum, pentacene organic field-effect transistors (OFETs) with BSA as gate dielectric exhibit a field-effect mobility value (µFE,sat) of 0.3 cm2 V-1 s-1 in the saturation regime and a threshold voltage (Vth) of approximately -16 V. BSA is easy to be hydrated in air ambient. Electrical properties of BSA in vacuum and hydrated BSA in air ambient are characterized. Similar to polyelectrolyte, hydrated BSA may interact with water to form H3O+ and OH- mobile ions. The hydrated BSA may act the gate dielectric with the formation of electric double-layer capacitors (EDLCs) to improve the device performance. In a relative humidity of 47%, the mobility value increases to 4.7 cm2 V-1 s-1 and the Vth reduces to -0.7 V. Generation of mobile ions in hydrated BSA and the formation of EDLCs are discussed. A higher back sweep current hysteresis was observed for pentacene OFETs with BSA as gate dielectric in air ambient. A phenomenon of “humidity induced hysteresis reduction” occurs based on the transfer data at different humidity. The phenomenon is attributed to improvement of ion movement based on quasi-static capacitance data measured in a humidity range from 0 to 60 %. A simple model regarding the movement of H3O+ and OH- mobile ions in response to the applied gate voltage is proposed to explain the transfer data of the OFETs. A novel package process has been developed tp keep pentacene OFETs with BSA as gate dielectric in a certain humidity environment in order to investigate the device performance at optimized humidity. The devices at humidity of 45% have the best performance with field effect mobility value of 2.85cm2V-1s-1, threshold voltage of -0.41V, and hysteresis shift of 0.24V. In contrast to OFETs packaged at humidity of 60%, the OFETs packaged at humidity of 45% get a longer life time as long as 100 days. The optimized humidity parameter is considered to be at 45% for pentacene OFETs with BSA as gate dielectric.