運用上光阻的奈米碳管場效電晶體作為離子濃度變化的感測器

Abstract

本研究設計及製備奈米碳管場效電晶體(CNTFET)，並藉由水溶液中不同的離子強度來研究和探討電晶體的特性。奈米碳管電晶體是藉由奈米碳管橫跨於兩個鈦電極( source和 drain )上來當作一個電子運輸路徑。實驗中我們藉由外加的閘極(liquid-gate)來探討上光阻(passivation)與沒上光阻的漏電流差別。我們發現光阻覆蓋在兩個鈦電極上，有效的抑制大約兩個級數的漏電流量。實驗中，去離子水(deionized water)和氯化鈉離子溶液 (NaCl)的量測電流明顯的不同。在進一步的實驗中，隨著不同的氯化鈉離子濃度(1x10-6M∼1M) ，奈米碳管場效電晶體之電性也有明顯的變化。實驗結果證明這個上光阻的奈米碳管電晶體能藉由外加的閘極來分離溶液中的電荷並以此來區分出離子的濃度差別。它也表示奈米碳管電晶體能區分由生物反應所造成的一些離子濃度變化，預期將可以設計成一靈敏的生物感測裝置。

A carbon nanotube field effect transistor (CNT FET) was designed, and fabricated, in this study where the characteristic of the device was examined in aqueous solution with distinct ionic strength. Carbon nanotubes, acting the channels of the FET, bridging across two Ti pad (source and drain) to form the CNT FET. We measured the leakage current in the devices with photoresist passivated and non-passivated under adding a liquid-gate. The passivated layer, formed over the source/drain electrode, greatly suppressed the gate leakage current by two to three orders of magnitude. The currents through the CNTs were noticeably different between two liquid samples: deionizeded water and aqueous solution (NaCl). Furthermore, the current obtained in aqueous solution with various concentration of NaCl (1x10-6∼1M) was evaluated. The results demonstrated that the passivated CNT FET was capable of determining the ionic concentration of aqueous solution under an additional voltage for inducing the separation of charges. It also implied that the CNT FET can be applied to detect the ions produced from specifically designed biological reactions. It is expected that the CNT FET can be designed into a highly sensitive bio-sensor.