First principles study of periodic size dependent band gap variation of Cu doped ZnO single-wall nanotube.

In this contribution, the size dependent band gap variation of (Zn(4/6)Cu(2/6)O)(L)/(Zn(5/6)Cu(1/6)O)(L) (L is the periodic size) superlattices are investigated with the change of L. The results show that the variation tendency of band gap appears a minimum in S(4) (L = 4) which is nearly a conductor. The band gap of S(3) (L = 3) and S(5) (L = 5) also decrease obviously compared to the other three configurations. Especially, the band gap of S(3) has decreased to 2.16 eV which is in the region of narrow bandgap semiconductor. Thus, the band gap can be modulated by alloying through constructing an appropriate variation period. Our ZnCuO superlattices can absorb light in both visible and UV region. These properties make the superlattices a potential application in photocatalysis and the visible light emitter.