Stage-by-stage formation of superficial nanostructures in ITO films reduced by H ₂ -GD at low temperature (100 °C) for applications on plastic substrates

The formation of superficial nanostructures (SNs) in reduced indium tin oxide (ITO) thin films by H₂-Glow discharge (GD) at a low reduction temperature (T_r = 100 °C) was investigated. Sputtered ITO films deposited at low (T_d = 100 °C) and high (T_d = 300 °C) temperatures were reduced using this low-temperature process. Scanning electron and atomic force microscopy were applied to study the evolution of the nanostructural features and three stages were identified: emerging/densification, coalescence, and depletion stages. The structural characteristics of the SNs were characterized by grazing incidence and conventional θ/2θ x-ray diffractions showing that at T_r = 100 °C, the reduction process was limited to the surface region in which the ion bombardment had influence. The mean diameter, , of the SNs in ITO deposited on the glass substrate was controlled from ∼10-90 nm and the SN densities, d, were obtained from ∼10⁹-10¹¹ SNs cm^-2. Finally, the superficial nanostructures were successfully formed in ITO films deposited on flexible polyethylene naphthalate (PEN) substrates. It was demonstrated that, on these substrates, is possible to obtain a uniform distribution in the size and density of the SNs, with = 9.5-20.7 nm and d = 2.66 × 10¹¹-4.20 × 10¹⁰ SNs cm^-2.