The diffusion behavior of ion implanted indium and silver atoms in ZnO crystals was reported. Both In and Ag ions were implanted at room temperature at 7 to 10° relative to the c-axis in order to avoid channelling effects during implantation. In ions were implanted at four different energies (40, 100, 200 and 350keV, respectively) and doses (4.20 x 1013, 6.70 x 1013, 8.10 x 1013 and 3.10 x 1014/cm2, respectively), resulting in a total dose of 5 x 1014/cm2. For another set of ZnO samples, Ag ions were implanted at energies 30, 75, 150 and 350keV at doses 3.3 x 1013, 4.2 x 1013, 8.3 x 1013 and 3.4 x 1014/cm2, respectively, to reach a total dose of 5 x 1014/cm2. Both In and Ag implants resulted in a uniform concentration profile of the implanted dopants from surface to a depth of ∼150nm. The samples were annealed for 30 minutes at between 850 and 1050C in an oxygen gas flow. The distributions of In and Ag atoms, either aligned or non-aligned along the crystalline directions, were measured by Rutherford backscattering combined with ion channelling. The diffusivities for non-aligned (interstitial) and aligned (substitutional) dopants atoms were determined to vary with annealing temperature via the Arrhenius relationship. The diffusion activation energies (Ea) along the <10•1> direction for substitutional impurity atoms were lower than those for interstitial dopants atoms e.g., in the case of In, Ea ∼ 1.52eV for <10•1> aligned In atoms and Ea ∼ 2.61eV for interstitial In atoms between <10•1> atomic rows and in the case of Ag, Ea ∼ 1.77eV for the interstitial Ag atoms between the <10•1> atomic rows and 1.11eV for <10•1> aligned Ag atoms. The diffusion activation energies exhibited a different trend for the two dopants as measured along the <00•1> crystalline direction. For Ag implanted in ZnO, the activation energy of Ea ∼0.91eV for the aligned Ag atoms along <00•1> direction and Ea ∼ 1.55eV were found for the interstitial Ag atoms, whereas in the case of In along the <00•1> direction, the interstitial In was found to migrate with a higher activation energy (Ea ∼1.78eV) than the substitutional In (Ea ∼1.42eV). These results were compared with first-principle calculations in order to understand the energetics of defect formation and migration in both n- and p-type doping cases.

Diffusion of Ion Implanted Indium and Silver in ZnO Crystals. Yaqoob, F., Huang, M.: Materials Research Society Symposium Proceedings, 2011, 1394, 101-7