Effect of Sb doping on the transport and electrochemical properties of partially amorphous SnO2 thin films

Sb-doped SnO2 thin films synthesized by sol-gel method were characterized physically and electrochemically. The crystallization was promoted by Sb incorporation in the lattice and the optical gap is blue-shifted due to the quantum confinement. The thermal variation of the electrical conductivity indicates a semiconducting behavior with relaxation process shifted to higher frequencies, typical of hopping mechanism of charge carriers. The hopping length R averages ~ 1.4 nm and the maximum barrier height (Wm) for the electronic jumps is 878 meV. The interfacial capacitance is characteristic of n-type behavior with an electrons density of 2.7 × 1019 cm−3 and a space charge region of 150 nm. The valence and conduction bands were found to be −0.89 and +2.95 VSCE respectively; they are pH sensitive and sweeping with respect to redox system. The impedance data revealed three distinct electrochemical behaviors with high diffusion process in doped samples marked by the increase of Warburg impedance (0.91-202.3 kΩ·cm2). The optimal band bending with respect to levels (H2O/H2, O2/H2O)
- ‐(O2/O2
- −, OH
- /H2O), was achieved with localized states mediating the charge exchange.