Using I-V characteristics to investigate selected contacts for SnO2:F thin films

Fluorine doped tin oxide（SnO₂:F） thin films were prepared on glass substrates by the spray pyrolysis （SP） technique at different substrate temperatures between 380+480℃.The microstructure of the films was explored using scanning electron microscope observations.An investigation of selected contacts for the films was performed through the analysis of the I-V measurements which were taken in the dark at room temperature.Indium, aluminum and silver were selected as contacts where two strips of each metal were vacuum-evaporated on the surface of the film.The resistivity of the films was estimated from the linearⅠ-Ⅴplots.It was found that the smallest resistivity was obtained using silver contacts,while the largest resistivity was obtained by using indium contacts.This is because silver diffuses in the film and participates in doping,while aluminum and indium cause compensation effects when they diffuse in the film.The best linear fit parameters are those of films with aluminum contacts,and the worst ones are those of films with indium contacts.Annealing was found to improve the electrical properties of the films,especially those deposited at a low substrate temperature.This is because it is expected to encourage crystal growth and to reduce the contact potential which leads to the formation of an alloy.Annealed films are more stable than un-annealed ones.