Key Lab of Inorganic Functional Materials and Devices, CAS
Defects characterization and engineering of zinc oxide
Prof. Francis Chi-Chung Ling
Department of Physics, The University of Hong Kong
ZnO is a direct band gap semiconductor having a wide band gap of ~3.4 eV and a large exciton binding energy which has recently received extensive because of its multi-functionality in a variety of applications, including optoelectronic, photovoltaic, spintronic, photocatalysis, sensor, transparent electrode, and transparent electronic, etc. Defects, either intrinsic or extrinsic impurity, plays crucial role in determining the materials’ electrical, optical, and magnetic properties. Moreover, the development of realistic ZnO-based device technology is hindered by the asymmetric difficulty in p-type doping, which is associated with the complexity of the shallow acceptor defects structures and the defect compensation. Despite of the essential role of defects, the knowledge of defects in ZnO is far from complete.
The present seminar aims to introduce our recent works on defect characterization, defect control and the engineering of functional defects in ZnO. Defect characterizations were performed using a comprehensive spectroscopic approach including positron annihilation spectroscopy (PAS), luminescence spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), temperature dependent Hall measurement, and deep level transient spectroscopy (DLTS) etc. Results of VZn-related defects in undoped ZnO (which is the important residual acceptor in undoped ZnO), the ferromagnetic Cu-VO-Cu defect complex in Cu-doped ZnO, and the XZn-(VZn)2 shallow acceptor complex (X=As and Sb) in the p-type X-doped ZnO will be discussed.