How spray rate influences the formation and properties of transparent conducting SnO2 thin films

- Spray rate determines the formation and composition of SnO2 thin films.
- Surface morphology is changing from small sharp structures to large blunt structures with increase in spray rate.
- Two order enhancement in carrier concentration and conductivity and a two fold increase in charge mobility with increase in spray rate.
- The cause of variation in the opto-electronic properties of SnO2 films with spray rate is identified by employing XPS.

Spray rate is rather a little-explored critical parameter in chemical spray pyrolysis (CSP). But interestingly it strongly influences formation and properties of the films. Hence in the present work, we report results of systematic analysis of changes in structural, electrical, optical, morphological and compositional properties of sprayed SnO2 films due to controlled variation in spray rate. We have observed two order enhancement in carrier concentration and conductivity and a two fold increase in charge mobility with increase in spray rate alone. Increase in carrier concentration with spray rate is also evident from the observed decrease in transmittance in IR region due to the increase in free carrier absorption. Analysis of the films using X-ray photo electron spectroscopy revealed increase in metal to oxygen ratio and reduction in unwanted oxygen species with spray rate.