16 Predict extrinsic semiconductivity for V2O5 and CoO A pty

16. Predict extrinsic semiconductivity for V2O5 and CoO.
A. p-type and n-type
B. p-type and p-type
C. n-type and p-type
D. n-type and n-type

Can someone explain how you determine which groups are n type or p type. What are the rules? the correct anwser should be C but why?

Solution

answer.   

in V2O5 the oxidation state is + 5 hence it can be easily reduced. It accepts O^2- ions which escape as elemental oxygen. The excess electrons enter a band formed from V d orbitalsresults in p type semicondctivity.

in CoO the oxidation state of cobalt is +2 which is a stable oxidation state hence it readily loses oxygen and is predicted to be n type semi conductor