Low-Voltage Organic Thin-Film Transistors Using a Hybrid Gate Dielectric Consisting of Aluminum Oxide and Poly(vinyl phenol)

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This study presents low-voltage organic thin-film transistors (OTFT) using a hybrid gate dielectric consisting of aluminum oxide and poly(vinyl phenol). Aluminum oxide with a thickness of 5 nm is directly formed on an aluminum gate electrode by an oxygen plasma process. The poly(vinyl phenol) film with a thickness of 10 nm is deposited on the aluminum oxide by a spin coating process. The proposed OTFTs are able to operate at low voltages lower than 5 V because of the thin gate dielectric. The surface of the hybrid gate dielectric is finished with a hydrophobic poly(vinyl phenol) so that a pentacene semiconductor, which is deposited on the gate dielectric, produces a high quality channel, resulting in a high mobility with 0.63 cm2 V-1 s-1. Additionally, the poly(vinyl phenol) layer reduces the leakage current through the gate dielectric, generating a low off-state current of 0.02 pA/μm and thus a high on/off current ratio of $4.4\times 10^{5}$. Finally, the pin-hole free poly(vinyl phenol) layer protects the thin aluminum oxide gate dielectric from being penetrated by source and drain electrodes; thus, an OTFT with a bottom contact structure is achieved with short channel length.
2010-11-25