Organic field-effect transistor bottom-contact

Figure 11.1 Schematic layout of organic field effect transistors with top (a) and bottom contacts (b).

Figure 18.1 Organic field effect transistor with bottom gate and bottom drain and source contacts.

DCNDBQT organic field effect transistors (OFETs) were fabricated on a highly doped n-Si wafer with 30 nm silicon dioxide. Firstly, the silicon surface was rinsed with Dl-water, acetone and iso-propanol in order to remove small particles and organic impurities. Secondly, the substrate was treated with oxygen plasma and silanised for 26 hours at 60 °C by hexamethyldisilazane (HMDS) in order to improve the OFET performance [21]. As source-drain contacts of the bottom contact transistors (BOC) gold was used, which was evaporated through a shadow mask on the silieon dioxide (see Figure 5.2). 

Li, T. et al.. Investigation of bottom-contact organic field effect transistors by two-dimensional device modeling, J. Appl. Phys., 93, 4017, 2003. 

Lindner, T., Paasch, G. and Scheinert, S., Influence of distributed trap states on the characteristics of top and bottom contact organic field-effect transistors, J. Mater. Res., 19, 2014-2027, 2004. 

Organic field effect transistor (OFET) devices have been fabricated from pBTTT polymer solutions and hole mobility values of up to 0.8cm /V s were reported in a nitrogen atmosphere. These values approach that of high performing evaporated small molecule devices and are comparable to amorphous silicon. In bottom gate, bottom-contact devices, in which the active semiconductor layer is the exposed top surface, the effect of different ambient conditions has been evaluated. Exposure to unpurified, ambient air in which the humidity is -50%, results in an initial increase in the off-current of the device. In filtered, low humidity air, transistor devices remain very stable over time. 

Fig. 29 a Top contact and b bottom contact field-effect transistor structures for determination of charge-transport properties of organic semiconductors, c Typical output characteristics and d transfer characteristics of an organic field-effect transistor with Spiro-TAD 61 as active material (measurements by T.P.l. Saragi)... 

As a low-cost alternative to traditional inorganic semiconductors based transistors, organic field effect transistors are ideally positioned for applications such as radio frequency ID tags, sensors, and smart banknotes [36-40]. An archetypical structure of a bottom-gate top-contact OFET is shown in Scheme 3.7a. Other device architectures have also been employed depending on the relative... 

P. Cosseddu and A. Bonfiglio. 2007. A comparison between bottom contact and top contact all organic field effect transistors assembled by soft lithography. Thin Sold Films 515 7551-7555. 

Cosseddu P, Bonfiglio A. Soft lithography fabrication of all-organic bottom-contact and top-contact field effect transistors. Appl Phys Lett 2006 88 23506.1-23506.3. 

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