Preparation of Low-Temperature Solution-Processed High-κ Gate Dielectrics Using Organic-Inorganic TiO2 Hybrid Nanoparticles

Abstract

Organic-inorganic hybrid dielectric nanomaterials are vital for OTFT applications due to their unique combination of organic dielectric and inorganic properties. Despite the challenges in preparing stable titania (TiO₂) nanoparticles, we successfully synthesized colloidally stable organic-inorganic (O-I) TiO₂ hybrid nanoparticles using an amphiphilic polymer as a stabilizer through a low-temperature sol-gel process. The resulting O-I TiO₂ hybrid sols exhibited long-term stability and formed a high-quality dielectric layer with a high dielectric constant (κ) and minimal leakage current density. We also addressed the effect of the ethylene oxide chain within the hydrophilic segment of the amphiphilic polymer on the dielectric properties of the coating film derived from O-I TiO₂ hybrid sols. Using the O-I TiO₂ hybrid dielectric layer with excellent insulating properties enhanced the electrical performance of the gate dielectrics, including superior field-effect mobility and stable operation in OTFT devices. We believe that this study provides a reliable method for the preparation of O-I hybrid TiO₂ dielectric materials designed to enhance the operational stability and electrical performance of OTFTs.

Keywords: OTFT; amphiphilic polymer; coating; colloidal; gate dielectric; hybrid; organic–inorganic; stable; titania.

Figure 1

Schematic presentation of the amphiphilic urethane polymer (AUP).

Figure 2

FT-IR spectra of the three AUPs.

Figure 3

Preparation of O-I TiO₂ hybrid nanoparticles in the presence of AUP.

Figure 4

Formation mechanism of O-I hybrid coating films.

Figure 5

XPS data spectra of (a) typical survey of O-I TiO₂ hybrid coating and (b) Ti2p; (c) TGA data.

Figure 6

Optical microscope images. (a) TiO₂/poly(AUP)—5 wt% coating; (b) TiO₂/poly(AUP)—10 wt% coating; (c) TiO₂/poly(AUP)—15 wt% coating; (d) UTi7-m550 coating; (e) UTi7-m750 coating; (f) UTi7-m2000 coating.

Figure 7

Dielectric constant of (a) O-I hybrid coating and (b) nanocomposite coating according to frequency; (c,d) leakage current density properties of O-I hybrid coating and nanocomposite coating, respectively.

Figure 8

(a) SEM images and (b) AFM topographic images of O-I hybrid coatings.

Figure 9

(a) Device schematic with UTi7-m550 as gate dielectric; (b) photographs of the large-scale OTFT arrays on Si wafer when using the spin-coating method; (c) electrical characteristics of C10-DNTT OTFT devices; (d) dielectrics’ transfer curve; (e) transfer curve with bias stress test.