Perspective Coatings Based on Structured Conducting ITO Thin Films for General Optoelectronic Applications

Abstract

In many electro-optical devices, the conductive layer is an important key functional element. Among others, unique indium tin oxide (ITO) contacts take priority. ITO structure is widely used as the optical transparent and electrically conductive material in general optoelectronics, biosensors and electrochemistry. ITO is one of the key elements in the liquid crystal (LC) displays, spatial light modulators (SLMs) and LC convertors. It should be mentioned that not only the morphology of this layer structure but also the surface features play an important role in the study of the physical parameters of the ITO. In order to switch the surface properties (roughness, average tilt angle and surface free energy) of the ITO via the laser-oriented deposition (LOD) method, carbon nanotubes (CNTs) were implanted. In the LOD technique, the CO2 laser (λ = 10.6 μm, P = 30 W) with the control electric grid was used. The switching of the deposition conditions was provided via the varying electrical strength of the control grid in the range of 100–600 V/cm. The diagnostics of the surfaces were performed using AFM analysis and wetting angle measurements. The components of the surface free energy (SFE) were calculated using the OWRK method. The main experimental results are as follows: the roughness increases with a rise in the electric field strength during the deposition of the CNTs; the carbon nanotubes provide a higher level of the dispersive component of SFE (25.0–31.4 mJ/m2 against 22.2 mJ/m2 in the case of pure ITO); the CNTs allow an increase in the wetting angle of the 5CB liquid crystal drops from 38.35° to 58.95°. Due to the possibility of the switching properties of the ITO/CNT surfaces, these modifications have potential interest in microfluidics applications and are useful for the liquid crystal’s electro-optics.