Investigation of migration energy barriers from the surface to bulk of self-assembly ZnO nanorods by multi-optical methods

Feng-Ming Chang^1*, Zong-Zhe Wu¹, Jing-Heng Huang¹, Wei-Ting Chen¹, Sanjaya Brahma¹, Kuang-Yao Lo¹

¹Physics, National Cheng Kung University, Tainan, Taiwan

* Presenter:Feng-Ming Chang, email:m331529@gmail.com

Post-annealing treatment plays an important role for self-assembly (SA) metal oxide by providing thermal energy for oxygen atoms to overcome the migration energy barrier. With theoretical methods, it’s hard to calculate the height of migration energy barrier from the surface to bulk which depends on depth. Due to the high surface-to-volume ratio of SA ZnO nanorods (ZNRs), the optical properties and structural evolution on the surface obtained by ultraviolet/X-ray photoemission spectroscopy (UPS/XPS) and photoluminescence (PL) could be well investigated and reveal mutual agreement in all results in PL, XPS and UPS. In this work, we first demonstrated structural variation on the surface of SA-ZNRs by scanning over a range of annealing temperatures and durations by rapid thermal annealing (RTA) system and then characterized the multi-optical properties by integrating the results of PL, XPS and UPS. Finally, the model of migration energy barriers reveals the well ZNRs formed at 570°C and the further oxidation process with formation of hydroperoxide on the Zn-rich surface of ZNRs at 640°C.

Keywords: Migration energy barriers, Ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), Photoluminescence (PL), Self-assembly ZnO nanorods