Understanding the thermodynamic pathways of SnO-to-SnOx phase transition

Abstract

SnO decomposes into SnO2 and Sn above a certain temperature either directly or through intermediate phases. This phase transition, although has been known for a century, is not well understood yet. Further, to date, a consensus on the correct stoichiometry and crystal structures of intermediate SnOx phases formed during that phase transition is absent. Our work attempts to elucidate SnO-to-SnOx phase transition at thermodynamic growth conditions for the first time. The results presented here show that oxygen-poor and tin-rich growth conditions promote SnO-to-SnOx phase transition to happen. At these growth conditions, indirect phase transition is the most probable, and in such transition, the formation of any (Sn2O3 or Sn3O4) intermediate phases is equally probable depending on initial growth conditions. All these findings are consistent with experimental results. Further, it was demonstrated that empirical van der Waals (vdW) correction of SnO is required to reproduce the pathways of this phase transition correctly. At the end, the opto-electronic properties of Sn2O3 have been investigated.