Organic Field-Effect Transistors with a Bilayer Gate Dielectric Comprising an Oxide Nanolaminate Grown by Atomic Layer Deposition

Abstract

We report on top-gate OFETs with a bilayer gate dielectric comprising an AlO /HfO nanolaminate layer grown by atomic layer deposition and an amorphous fluoro-polymer layer (CYTOP). Top-gate OFETs display average carrier mobility values of 0.9 ± 0.2 cm/(V s) and threshold voltage values of -1.9 ± 0.5 V and high operational and environmental stability under different environmental conditions such as damp air at 50 °C (80% relative humidity) and prolonged immersion in water at a temperature up to 95 °C.

Stable organic thin-film transistors

“…Specifically, we have shown that, when this second gate dielectric layer comprises a single metal oxide (for example, Al 2 O 3 ) processed by atomic layer deposition (ALD), n- and p-channel μc-OTFTs operate at low-voltage values with good operational stability and excellent environmental stability, remaining functional after being subjected to oxygen plasma for several minutes and being immersed in water for several hours ( 13 ). Furthermore, when the second gate dielectric layer comprises a first layer of Al 2 O 3 by ALD, deposited on CYTOP, and a second nanolaminate (NL) layer comprising nanometer-thick alternating layers of Al 2 O 3 and HfO 2 by ALD, μc-OTFTs can even sustain immersion in water at 95°C for tens of minutes ( 12 ). Here, we build on this approach by showing that μc-OTFTs with an optimized bilayer gate dielectric comprised of a first CYTOP layer and a second Al 2 O 3 :HfO 2 NL layer grown by ALD display improved environmental stability and unprecedented operational stability, with V TH shifts that are comparable to or smaller than the ones reported in the scientific literature for μc-Si and a-oxide TFTs over time.…”

A review of highly reliable flexible encapsulation technologies towards rollable and foldable OLEDs

“…The ALD process allows the deposition of few-nanometers-thick, uniform ultra-thin layers with thickness control at the angstrom level. Starting [64,[78][79][80]. The proposed nanolaminate structures have shown improved barrier performance compared to a single layer.…”

Top-gate organic field-effect transistors fabricated on paper with high operational stability

“…Top-gate bottom-contact OFETs with the structures shown in Figure 1 Figure 2 shows representative transfer and output characteristics of type-1 (Figure 2 (a) and (c)) and type-2 OFETs (Figure 2 [17,18,20] or plastic substrates [21]. Since the surface of the HD 230 paper substrates is smooth, differences in device performance are expected to be related to differences in morphology during the formation (i.e.…”

“…air or water) will eventually lead to changes of the device performance, which in the past, have been exploited to develop sensors [16], but are less desirable to develop reliable electronic circuits. For this reason, we believe that the use of a topgate OFET geometry is particularly attractive because, as we have shown, in this geometry the organic semiconductor layer is protected from the environment while at the same time, the gate dielectric can be engineered to enable top-gate OFETs to operate at low voltage values and to display exceptional operational and environmental stability even in aqueous environments [17][18][19][20]; as well as when fabricated on plastic [21] or on cellulose nanocrystal (CNC) substrates [11].…”