Question

Non-stoichiometric cuprous oxide, Cu₂O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2 : 1. Can you account for the fact that this substance is a p-type semiconductor?

Answer 1

Some cuprous (Cu⁺) ions have been replaced by cupric (Cu²⁺) ions when the copper to oxygen ratio in Cu₂O is less than 2 : 1. Since each Cu²⁺ ion entering the lattice must replace two Cu⁺ ions in order to preserve electrical neutrality, creating an electron-deficient hole, this suggests that there must be cation vacancies in the lattice. Consequently, the crystal would function as a p-type semiconductor and conduct electricity via the motion of electron-deficient (positive) holes.