Na mole concentration dependence on optical p-type behaviors of Na-doped ZnO nanowires

We report the structural and optical features of Na-doped ZnO nanowires as a function of Na mole concentration to demonstrate the p-type conduction of Na-doped ZnO nanowires. The samples are prepared on RF-sputtered ZnO seed layers by using a simple hydrothermal method with sodium nitrate, zinc nitrate, and hexamethylenetetramine (HMTA) in an aqueous solution at low temperature (<90 °C). At first, the crystal structure of the c-axis orientation was analyzed using X-ray diffraction patterns. These exhibited a slight shift to lower values of the diffraction angle with decreasing Na mole concentration. To further verify the p-type behaviors of Na-doped ZnO nanowires, cryo-photoluminescence was employed at temperatures ranging from 10 to 300 K, corresponding to the clear appearance of excitons bound to a deeper acceptor (AD0X) and its LO phonon replicas.This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2013R1A1A2060350)