Structure, Optical and Electrical Properties of Nb(Zn) Doped Sol–Gel ITO Films: Effect of Substrates and Dopants

Abstract

We present comparative studies of sol–gel ITO multilayered films undoped and doped with Nb or Zn (4 at.%). The films were obtained by successive depositions of five layers using the dip-coating sol–gel method on microscopic glass, SiO2/glass, and Si substrates. The influence of the type of substrates and dopant atoms on the structure and optical properties of the sol–gel ITO thin films is examined and discussed in detail. XRD patterns of these layers showed a polycrystalline structure with an average crystallite size of <11 nm. Raman spectroscopy confirmed the chemical bonding of dopants with oxygen and showed the absence of crystallized Nb(Zn)-oxide particles, indicated by the XRD pattern. Spectroscopic Ellipsometry and AFM imaging revealed a clear dependence of the optical parameters and surface morphology of the ITO and ITO:Nb(Zn) thin films on the type of substrates and dopants. The analysis of the current-voltage and capacitance-voltage characteristics of the Al/ITO/Si structures revealed the presence of charge carrier traps in the ITO bulk and the ITO-Si interface. The densities of these traps are obtained and the character of the current transport mechanism is established.

Keywords

• sol–gel films
• Nb(Zn) doped ITO thin films
• microstructure
• optical properties
• electrical properties