Damage Mechanisms of Ion Implanted Bulk (0001) ZnO Single Crystals.
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Damage Mechanisms of Ion Implanted Bulk ( 0001) ZnO Single Crystals. B.T. Adekore1, I. Usov2, B. Patnaik2, N. Parikh2, and R.F Davis1. 1 Department of Materials Science and Engineering. North Carolina State University, NC 276957907, U.S.A. 2 Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, U.S.A.
ABSTRACT Crystalline damage created by ion-implantation of dopant impurities in ZnO ( 0001 ) substrates was characterized as a function of atomic mass of implanted species using triple-axis (2θ-ω/ω) xray diffraction and Rutherford backscattering (RBS). The former revealed the presence of implantation-induced strain through the broadening of the isometric and asymmetric 2θ-ω reflections. However, RBS indicated that the damage introduced during implantation of these ions was insufficient to transform the crystalline lattice into a completely amorphous state. Additional XRD characterization as a function of annealing temperature of the implanted materials showed a reduction in the broadening of the isometric reflections, indicating that structural recovery of implanted ZnO crystals can be achieved. INTRODUCTION Ion-implantation has again been recently employed as a technique of introducing extrinsic impurities into ZnO. It is has been recognized by few investigators [1] that in addition to its softness, the wide bandgap material demonstrates a notable resilience to implantation damage. It is thus difficult to achieve complete amorphization of the material upon implantation. It is of interest to investigators of impurity activation in ZnO to thermally recover the crystal and thereby at the best eliminate or at the least minimize the electronic contributions of ionimplantation induced defects. We utilize primarily triple axis x-ray diffraction (TAXRD) to quantitatively investigate the broadening in the full width at half maximums (FWHM) of both the azimuthal, RC3(ω), and radial, RC (2θ-ω), intensity distribution. We define the onset of structural recovery as the temperatures at which an abrupt or graded decrease in the FWHM of both distributions commences. We employed Rutherford backscattering spectroscopy as a secondary technique of investigating the nature of the damage. However, because of the much resolved sensitivity of RBS to heavier implants and the progressive alleviation of implantation damage with annealing temperature, RBS was utilized solely as a qualitative rather than a quantitative technique of evaluating the implantation damage. Silver implantation into ZnO is reported here as a representative study wherein both RBS and TAXRD can be meaningfully employed. EXPERIMENTAL DETAILS _
ZnO ( 0001) bulk crystals implanted with Lithium, Nitrogen, Sodium, Aluminum, Argon and Silver were used to investigate implantation damage as function of atomic mass of the species from lithium (6.941g.mol-1) to Silver (107.8662g.mol-1) as well as annealing temperature in 3
RC- rocking curves
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1Atm of oxygen at 25ºC (As-implanted) and 250ºC-1000ºC at an increment, ∆T= 150ºC.
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