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Balancing Surface Hydrophobicity and Polarizability of Fluorinated Dielectrics for Organic Field‐Effect Transistors with Excellent Gate‐Bias Stability and Mobility
Author(s) -
Jang Mi,
Lee Minjung,
Shin Hwanho,
Ahn Joongyu,
Pei Mingyuan,
Youk Ji Ho,
Yang Hoichang
Publication year - 2016
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201600284
Subject(s) - materials science , pentacene , dielectric , electron mobility , surface energy , polarizability , gate dielectric , field effect transistor , copolymer , substrate (aquarium) , polymer , transistor , chemical engineering , optoelectronics , thin film transistor , nanotechnology , organic chemistry , molecule , composite material , voltage , chemistry , oceanography , layer (electronics) , quantum mechanics , geology , physics , engineering
It is demonstrated that treating dielectrics with fluorinated polymers, which have excellent hydrophobicity, chemical inertness, and the lowest polarizability, yields a semiconductor‐compatible surface energy and excellent charge detrapping characteristics. Fluorocopolymers, polystyrene‐ random ‐poly(2,3,4,5,6‐pentafluorostyrene) (PS‐ r ‐PPFS) copolymers with different 2,3,4,5,6‐pentafluorostyrene (PFS) loadings, are synthesized to modify a SiO 2 gate dielectric using radical polymerization. Surface energy ( γ ) of the copolymer‐treated SiO 2 dielectrics decreases from 40.7 to 24.0 mJ m −2 with increasing PFS mol% in the copolymer. Pentacene organic field‐effect transistors (OFETs) show field‐effect mobility ( μ FET ) values ranging from 0.82 (for 0 mol% PFS) to 0.25 cm 2 V −1 s −1 (for 100 mol% PFS). Enhancing the bias stress stability without affecting the μ FET value is achieved via the introduction of a small mol% fluorocarbon segments onto the PS‐ r ‐PPFS backbone. 15 mol% PFS‐loaded fluorocopolymer‐coated SiO 2 substrate yields a γ value of 35 mJ m −2 , close to that (38 mJ m −2 ) of the lowest‐ γ crystal surface of pentacene, and the corresponding OFETs have μ FET values up to 0.81 cm 2 V −1 s −1 and excellent gate‐bias stress stability in comparison to the rich fluorinated dielectric systems, which has degraded μ FET values ranging from 0.2 to 0.4 cm 2 V −1 s −1 .