以牛血清蛋白作為閘極介電材料之有機場效電晶體研究

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

李雋毅

指導教授 ： 黃振昌

國立清華大學/工學院/材料科學工程學系/博士(2014年)

摘要

在本研究中，作者以牛血清蛋白（bovine serum albumin）做為軟性固態電解質介電材料以提升五苯環電晶體元件效能，元件在真空環境下閥值電壓約為-16.4 V、載子遷移率約為0.3 cm2V-1s-1，然而，在RH47%大氣環境下，元件的閥值電壓約為-0.7 V、載子遷移率約為4.7 cm2V-1s-1，在大氣環境中元件效能提升的原因可由電雙層模型解釋之。牛血清蛋白的酸性與鹼性胺基酸殘基可與水分子反應產生H3O+與OH-可移動離子，當可移動離子響應外界電場而移動至半導體-介電層介面形成電雙層時，可導致電晶體操作電壓降低，並且提升電晶體通道載子累積能力，使介面載子陷阱被填補進而使載子遷移率上升。

此外，作者透過能夠包裹水氣於封裝模組內的新穎封裝製程，控制濕度以調控電晶體效能並且減少不利於電路設計的電遲滯效應，得到最佳化的濕度參數約為RH45%，其元件載子遷移率為2.85 cm2V-1s-1，閥值電壓為-0.41 V，電遲滯約0.24 V。在RH45%的元件可靠度測試中，元件可操作50次不會有明顯衰退，其開電流維持在約4×10-6 A，載子遷移率維持在2.85 cm2V-1s-1，此外，透過封裝製程的控制，元件的使用壽命在RH45%的濕度環境下亦可以維持100天以上效能不衰退。

關鍵字

有機場效電晶體 ； 蛋白質 ； 牛血清蛋白 ； 五苯環

並列摘要

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.

並列關鍵字

OFET ； protein ； bovine serum albumin ； pentacene

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