Mirza Misbah, Wang Jiawei, Li Dexing, Arabi S Atika, Jiang Chao
CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Centre for Nanoscience and Technology , No. 11 Beiyitiao Zhongguancun, Beijing 100190, China.
ACS Appl Mater Interfaces. 2014 Apr 23;6(8):5679-84. doi: 10.1021/am5001954. Epub 2014 Apr 9.
We report on the fabrication of an organic field-effect transistor (OFET) of a monolayer pentacene thin film with top-contact electrodes for the aim of ammonia (NH3) gas detection by monitoring changes in its drain current. A top-contact configuration, in which source and drain electrodes on a flexible stamp [poly(dimethylsiloxane)] were directly contacted with the monolayer pentacene film, was applied to maintain pentacene arrangement ordering and enhance the monolayer OFET detection performance. After exposure to NH3 gas, the carrier mobility at the monolayer OFET channel decreased down to one-third of its original value, leading to a several orders of magnitude decrease in the drain current, which tremendously enhanced the gas detection sensitivity. This sensitivity enhancement to a limit of the 10 ppm level was attributed to an increase of charge trapping in the carrier channel, and the amount of trapped states was experimentally evaluated by the threshold voltage shift induced by the absorbed NH3 molecular analyte. In contrast, a conventional device with a 50-nm-thick pentacene layer displayed much higher mobility but lower response to NH3 gas, arising from the impediment of analyte penetrating into the conductive channel, owing to the thick pentacene film.
我们报道了一种用于检测氨气（NH₃）的有机场效应晶体管（OFET）的制备，该晶体管由单层并五苯薄膜和顶部接触电极组成，通过监测漏极电流的变化来检测氨气。采用顶部接触结构，即柔性印章[聚二甲基硅氧烷]上的源极和漏极电极直接与单层并五苯薄膜接触，以保持并五苯排列有序并提高单层OFET的检测性能。暴露于NH₃气体后，单层OFET沟道处的载流子迁移率降至其原始值的三分之一，导致漏极电流下降几个数量级，极大地提高了气体检测灵敏度。这种灵敏度提高到10 ppm水平的极限归因于载流子沟道中电荷俘获的增加，并且通过吸收的NH₃分子分析物引起的阈值电压偏移实验评估了俘获态的数量。相比之下，具有50 nm厚并五苯层的传统器件表现出更高的迁移率，但对NH₃气体的响应较低，这是由于并五苯薄膜较厚阻碍了分析物渗透到导电沟道中。
