Equilibrium potential of free charge carriers in a bent piezoelectric semiconductive nanowire.

We have investigated the behavior of free charge carriers in a bent piezoelectric semiconductive nanowire under thermodynamic equilibrium conditions. For a laterally bent n-type ZnO nanowire, with the stretched side exhibiting positive piezoelectric potential and the compressed side negative piezoelectric potential, the conduction band electrons tend to accumulate at the positive side. The positive side is thus partially screened by free charge carriers while the negative side of the piezoelectric potential preserves as long as the donor concentration is not too high. For a typical ZnO nanowire with diameter 50 nm, length 600 nm, donor concentration N(D) = 1 x 10(17) cm(-3) under a bending force of 80 nN, the potential in the positive side is <0.05 V and is approximately -0.3 V at the negative side. The theoretical results support the mechanism proposed for a piezoelectric nanogenerator. Degeneracy in the positive side of the nanowire is significant, but the temperature dependence of the potential profile is weak for the temperature range of 100-400 K.