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ORaCEL Seminar – Sara Pazoki
September 10, 2018 | 11:30 am - 12:30 pm
The Impact of Electrical Contacts on Morphology and Charge Transport in Ultrathin C8-BTBT Transistors
Research in 2D organic material has been an exciting field for many years. Understanding of charge transport process in 2D material can be used to test phenomenological transport models . Recently, small molecule 2,7-dioctylbenzothieno[3,2-b]benzothiophene (C8-BTBT) has shown a good performance in 2D OFET’s with hBN gates (mobility ⁓ 30 ) along with a band-like temperature dependence of mobility in the first monolayer . However, in ultrathin devices, thickness dependent of contact resistance requires special attention.
We observe contact related phenomena in C8-BTBT OFET’s created by organic molecular beam deposition. We note a very strong thickness dependence of mobility on C8-BTBT OFET’s which is in contrast with the known fact that mobility saturates after 2-6 layers of an OFET channel. Inspection with Atomic Force Microscopic reveals Au top-contacts sink beneath pre-deposited C8-BTBT without any damage to the molecular film morphology. This is the reason behind the unexpected thickness dependence of carrier mobility and emphasizes the fact that charge injection from the electrode to semiconductor plays a key role in the functionality of a device.
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