Pyrosol deposition of fluorine-doped tin dioxide thin films

Abstract

Fluorine-doped tin dioxide (SnO₂∶F) films were deposited from a tin tetrachloride solution in methanol utilizing a pyrosol deposition process. It is shown from thermodynamic calculations that the atmosphere during deposition is oxygen-rich and also suggested that chlorine and hydrogen chloride, which are produced during the deposition reaction, influence crystal growth. Detailed electrical, optical and structural properties of the material with respect to varying film thickness and substrate temperature are presented and discussed. Resistivity of the films deposited at 450 °C decreased from 6×10⁻⁴ to 2×10⁻⁴ Ωcm, while the mobility increased from 14 to 45 cm²V⁻¹s⁻¹, respectively, when the film thickness was varied from 100 to 1650 nm. The carrier concentration was relatively unchanged for film thicknesses higher than 200 nm. Optimized SnO₂∶F films (∼600 nm) having a resistivity of ∼6×10⁻⁴ Ωcm, a carrier mobility of ∼20 cm²V⁻¹s⁻¹, a carrier concentration of ∼8×10²⁰ cm⁻³ and a transmittance in excess of 80% are quite suitable as electrodes for amorphous silicon solar cells.