Pure silicon at $0\text{K}$ behaves as a/an:

Pure silicon is an intrinsic semiconductor. At absolute zero temperature ($0\text{K}$), there is no thermal energy available to break covalent bonds or excite electrons from the valence band to the conduction band. Because the conduction band remains completely empty and the valence band is completely full with no free charge carriers, pure silicon behaves as a perfect insulator at $0\text{K}$.