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In this paper, we demonstrate an effective method for the performance improvement of organic thin film transistors (OTFTs), in which the SiO2 dielectric layer was dually modified with polystyrene (PS) and hexamethyldisilazane (HMDS) self-assembled monolayer. The relationship between interfacial modification and device performance of OTFTs was systematically investigated. With the dual HMDS/PS modification, the SiO2 dielectric film turns from intrinsically hydrophilic surface to hydrophobic one. Moreover, the dual HMDS/PS modification induces the ordered growth of pentacene layer with large grains up to about 1.5 μm. As a result, the performance of OTFTs is remarkably enhanced, such as the increase in charge carrier mobility from 0.56 to 1.05 cm2/Vs and the increase in on/off current ratio from 105–106 to 106–107. These results indicate that the dual interfacial modification of dielectrics is a simple and effective approach for the OTFT performance improvement.

In this paper, nanostructured ZrO2 films were prepared by electron beam evaporation with the glancing angle deposition (GLAD) technique. Columnar films with voids in between formed owing to the self-shadowing effect and the limited diffusion of deposited atoms. The microstructure evolves from slanted columnar structure to helical and pillar structures as the substrate rotational speed increases. The diameter of the columns is in the range of 30–50 nm. A higher rotational speed favors a larger nodule size and a greater surface roughness. Due to the porous structure, the refractive index n of GLAD ZrO2 films varies from 1.75 to 1.80, lower than that of bulk material. A maximum value of birefringence (Δn=0.03) is obtained in a slanted columnar structure, and the relationship between birefringence and microstructure orientation is discussed. Our results demonstrate that glancing angle deposition is a feasible approach for designing the nanostructure and optical properties of thin films.