Chemically Tunable Organic Dielectric Layer on an Oxide TFT: Poly(p-xylylene) Derivatives

Abstract

Inorganic materials such as SiO x and SiN x are commonly used as dielectric layers in thin-film transistors (TFTs), but recent advancements in TFT devices, such as inclusion in flexible electronics, require the development of novel types of dielectric layers. In this study, CVD-deposited poly­(p-xylylene) (PPx)-based polymers were evaluated as alternative dielectric layers. CVD-deposited PPx can produce thin, conformal, and pinhole-free polymer layers on various surfaces, including oxides and metals, without interfacial defects. Three types of commercial polymers were successfully deposited on various substrates and exhibited stable dielectric properties under frequency and voltage sweeps. Additionally, TFTs with PPx as a dielectric material and an oxide semiconductor exhibited excellent device performance; a mobility as high as 22.72 cm2/(V s), which is the highest value among organic gate dielectric TFTs, to the best of our knowledge. Because of the low-temperature deposition process and its unprecedented mechanical flexibility, TFTs with CVD-deposited PPx were successfully fabricated on a flexible plastic substrate, exhibiting excellent durability over 10000 bending cycles. Finally, a custom-synthesized functionalized PPx was introduced into top-gated TFTs, demonstrating the possibility for expanding this concept to a wide range of chemistries with tunable gate dielectric layers.

Preparation of Hydrophobic Metal–Organic Frameworks/Parylene Composites as a Platform for Enhanced Catalytic Performance

“…Figure 1f shows the FT-IR spectra of UiO-66-NH 2 , UiO-66-NH 2 -PN-5, and parylene-N. The absorption bands at 2800−3000 cm −1 are attributed to the C−H stretching vibration of parylene-N. 35 The peak at 824 cm −1 belongs to the out-of-plane bending vibrations of the C−H bond of p-xylene. These characteristic peaks confirm the successful deposition of parylene-N onto the UiO-66-NH 2 .…”

“…Fourier-transform infrared (FT-IR) studies were further conducted to confirm the successful deposition of the parylene-N. Figure f shows the FT-IR spectra of UiO-66-NH 2 , UiO-66-NH 2 -PN-5, and parylene-N. The absorption bands at 2800–3000 cm –1 are attributed to the C–H stretching vibration of parylene-N . The peak at 824 cm –1 belongs to the out-of-plane bending vibrations of the C–H bond of p-xylene.…”

Fabrication of Zigzag Parylene Nanofibers in Liquid Crystals with Electric Field-Induced Defect Structures

“…Recently, the implementation of fiber structures has been achieved using the chemical vapor polymerization (CVP) method, where the orientation-controlled LC structures with the surface treatment are used as templates. − This development holds significant importance as it demonstrates the potential to produce unique surface structures such as oriented polymeric fiber with diverse functionalities using the various parylene monomers having specific functional moieties through the well-established CVP process. − In the CVP process, the polymerization reaction occurs at the interface through loaded precursors, which penetrate the LC molecules and grow along the long-range order of the LC template. The LC directors as ‘scaffolds’ can be controlled to create a variety of polymer fibrillar structures using external stimuli.…”

Organic/Inorganic Hybrid Top-Gate Transistors with Ultrahigh Electron Mobility via Enhanced Electron Pathways

“…Polymer dielectrics have attracted considerable attention as gate dielectrics for top-gate TFTs owing to their suitable properties for flexible displays. Among them, poly­(para-xylylene) (PPx) has been reported as a promising candidate with an adequate dielectric constant and low leakage current. − In 1965, Gorham devised a route of polymerizing PPx using PPx dimers via chemical vapor deposition (CVD) in a method that required no solvents or other additives . PPx fabricated using CVD can provide a thin, conformal, pinhole-free, and robust film, leading to the formation of interfaces that are compatible with oxide materials without incurring plasma damage.…”