A study of thermal decomposition of sputtered NiO films

¹ National Synchrotron Radiation Research Center (NSRRC) - Hsinchu 30076, Taiwan
² Department of Electrical Engineering, National University of Tainan - Tainan 70005, Taiwan
³ Department of Materials Science and Engineering, National Cheng Kung University - Tainan 70101, Taiwan
⁴ Institute of Physics, Academia Sinica - Taipei 11529, Taiwan

^a dong.cl@nsrrc.org.tw

Received: 21 April 2011
Accepted: 12 September 2011

Abstract

NiO films were deposited by radio-frequency reactive magnetron sputtering from a NiO target. A decomposition reaction was found as the films annealed at 400 °C in vacuum. The decomposition increased with increasing annealing temperature and the non-stoichiometry of the film. The electronic and atomic structure of the annealed films were further investigated by X-ray absorption near-edge structure (XANES) spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The results show the decomposition of sputtered NiO is attributed to excess vacancies that formed during sputtering, which destroyed the atomic bonds in the NiO crystalline. The EXAFS results indicate that there is a transition stage of surplus Ni ions filling anion sites at the beginning of the decomposition reaction. The surplus Ni ions act as a link between the central atom and the Ni in the second shell, which may be responsible for the filamentary conducting paths proposed in resistive random access memory (ReRAM).