The growth of tin oxide films by reactive ion-assisted deposition

Substoichiometric undoped SnOx (x<2) thin films were deposited on Si (100) substrate using reactive ion-assisted deposition. The effect of oxygen contents and heat treatment on the final crystalline structure of tin oxide films were investigated. Oxygen to Sn metal atomic ratios (N-O/N-Sn) of the as-deposited thin films were changed from 1.14 to 1.91 by varying the relative arrival ratio (Gamma) of oxygen ion to Sn metal, i.e., the average energy (E-a) impinging on each depositing Sn metal. Heat treatment was performed in two different ways; the first was post-annealing at 400 similar to 600 degrees C in a vacuum similar to 5 x 10(-3) Torr and the second was in-situ substrate heating. In case of post-annealing, perfect oxidation of SnO2 was found at 600 degrees C annealing. And it was found that the oxidation from SnO and SnO2 was largely dependent on the initial oxygen contents and annealing temperature. Temperature of tin oxide formation could be reduced as low as 400 degrees C by assisting energetic oxygen ion through in-situ annealing. Surface microstructure of the deposited films were also discussed in terms of average impinging energy and annealing temperature.