Lattice sites of implanted Cu and Ag in ZnO

Abstract

The group Ib impurities Cu and Ag on substitutional Zn sites are among possible candidates for p-type doping of ZnO. In order to explore possible lattice sites of Cu and Ag in ZnO the radioactive impurities 67 Cu and 111 Ag were implanted at doses of 4×10 12 cm −2 to 1×10 14 cm −2 at 60 keV into ZnO single crystals. The emission channeling effects of β − particles from the decay were studied by means of position-sensitive electron detectors, giving direct evidence that in the asimplanted state large fractions of Cu and Ag atoms (60-70% for Cu and 30% for Ag) occupy almost ideal substitutional Zn sites with root mean square (rms) displacements of 0.014-0.017 nm. However, following vacuum annealing at 600°C and above both Cu and Ag were found to be located increasingly on sites that are characterized by large rms displacements (0.03-0.05 nm) from Zn sites. We conclude that in high-temperature treated ZnO Cu and Ag are most likely not simply replacing Zn atoms but are incorporated in complexes with other crystal defects or as clusters.

Ag and N acceptors in ZnO: Anab initiostudy of acceptor pairing, doping efficiency, and the role of hydrogen

“…2b), the large shift of Ag brakes the axial symmetry, and both H and Ag are displaced from symmetric sites, which can explain the observations of Ref. [9]. We also find that hydrogen binds preferentially to N, and the energy of N-H is lower by 0.2 eV than that of the Ag-H configuration.…”

“…Ag doping was studied in Refs. [1][2][3][4][5][6][7][8][9], and its acceptor character was confirmed. In particular, ZnO:Ag layers grown by sputter deposition are p-type with concentrations up to 10 18 cm -3 and hole mobilities of about 1 Vm/sec 2 .…”

Identification of a Deep Acceptor Level in ZnO Due to Silver Doping

“…In films grown at 600°C, most of the Ag (94%) was incorporated substitutionally on Zn sites at a doping concentration of 1.5 9 10 19 Ag atoms/cm 3 , significantly higher than previously reported (30%). 24 It is highly desirable that most of the Ag is incorporated as Ag Zn , which has been theoretically predicted to be an acceptor in ZnO. 8,9 When the doping concentration is increased by an order of magnitude, Ag Zn increases proportionately, confirming the high solubility of Ag in the ZnO lattice.…”

Unambiguous identification of the role of a single Cu atom in the ZnO structured green band

“…22 While the exact defect structure remains unknown our studies, and other reports in the literature, suggest that the defect chemistry of Cu in ZnO is quite complicated and that Cu may exist in ZnO in a variety of charge states, lattice sites and complexes with other defects and impurities. [16][17][18][19][20][21] For example, we have grown ZnO nanorods using a carbothermal reduction-based vapour phase transport (VPT) process and have doped the deposited material by introducing Cu into the source powder prior to VPT growth by a modified Pechini process. Directly after growth there is only a very weak SGB emission.…”