Hello everybody and welcome to my first thread. I have read several publications regarding this compound, and found that SnO2 behaves as n-type semiconductor (Eg 3.6 eV) when oxygen vacancies are present. Very summarized and simply put, I understood that this lack of oxygen atoms enhance the movility of the electrons (of the sorrounding Sn/O) which would interact with them (by 'them' I mean the absent oxygen atoms), allowing them to reach the conduction band when thermally activated, increasing the number of charge carriers. Wrong or rather not, my first request would be a better explanation of this, expanding what I have said or rather correcting it. On a second plane, stoichiometric, defect-free SnO2 would be a normal insulator, with a high resistance value. Which would be the natural state of SnO2, insulator or semiconductor? I mean, the oxygen vacancies are natural or rather only attainable artificially when fabricating the crystal (on thin films, nanostructures, for example). What kind of SnO2 would I have, for example, in regular Ag/SnO2 contact materials (produced by powder metallurgy or internal oxidation)? Thank you very much in advance.