We have investigated the pentacene based Organic Thin Film Transistors (OTFTs) with High-k Dielectric Nd 2 O 3 . Use of high dielectric constant (high-k) gate insulator Nd 2 O 3 reduces the threshold voltage and sub threshold swing of the OTFTs. The calculated threshold voltage -2.2V and sub-threshold swing 1V/decade, current ON-OFF ratio is 1.7 × 10 4 and mobility is 0.13cm 2 /V.s. Pentacene film is deposited on Nd 2 O 3 surface using two step deposition method. Deposited pentacene film is found poly crystalline in nature.
In this work, we have studied the electrical performance of cross-linked polyvinyl phenol (cPVP) modified lanthanum oxide (La2O3) bilayer dielectric film in pentacene thin film transistors (TFT). A simple spin-coating and room temperature operated cross-linking reaction of the hydroxyl moieties of PVP and the nitrogen groups of PMF were carried out to form the cross-linked PVP. The deposition of a thin 30 nm cPVP layer over the La2O3 layer provided a low leakage current (<10−7A/cm2), causing a reduction in the interface trap density. Besides, the modified surface properties of the La2O3 layer were favorable for the growth of pentacene organic semiconductors. As a result, the current on-off ratio and the sub-threshold slope was improved from 104 and 1.0 V/decade to 105 and 0.67 V/decade. The La2O3∕cPVP pentacene TFT operated at −10 V also exhibited improvement in the field-effect mobility to 0.71 cm2/Vs from 0.48 cm2/Vs for the single-layer La2O3 (130 nm) device. Thus, our work demonstrates that the rare earth oxide La2O3 with cPVP is an excellent dielectric system in the context of emerging transistors with hybrid polymer gate dielectrics.
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