On the development of the <111> fiber texture in nanocrystalline gold during growth and annealing

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On the development of the fiber texture in nanocrystalline gold during growth and annealing Klaus P. Andreasen1, Norbert Schell2, Thomas Jensen1, Jakob H. Petersen1, Martin S. Jensen1, Jacques Chevallier1 and J. Bøttiger1 1 Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark 2 Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, P.O. Box 510119, D-01314 Dresden, Germany ABSTRACT The evolution during growth and subsequent annealing of the fiber texture in magnetron-sputtered nanocrystalline Au films has been studied experimentally using X-ray diffraction with synchrotron radiation. To quantitatively investigate this fiber texture, grain orientation distributions were recorded in situ during growth and during subsequent annealing using Bragg-Brentano geometry. The (111) diffraction intensity was measured as a function of the sample tilt χ, the tilt axis lying at the intersection of the film surface and the scattering plane. As a quantitative measure of the texture, we used the width of the orientation distributions. The grain-orientation distributions narrowed during annealing. The activation energy for the process behind this texture change was found to be 0.64 ± 0.05 eV, close to the activation energy for grain boundary self-diffusion in nanocrystalline Au. This and the narrowing of the grain orientation distributions led us to suggest that the observed changes in texture originated from grain rotations and not from grain growth. Grain growth did not take place at the lower temperatures, where changes in orientation distributions were observed.

INTRODUCTION Nanocrystalline materials have very small grain sizes between a few nanometers and 100 nm. This results in materials with unique properties and a great potential for industrial applications [1]. The nanostructure – including any texture – has to be tailored to specific applications, since it strongly influences the physical and chemical properties. This requires knowledge of the dependence of the nanostructure on the deposition parameters and an understanding of the mechanisms that control the formation and evolution of the nanostructure. Gold was chosen as a nanocrystalline model material (no oxidation) with which we studied the formation and evolution of the nanostructure during growth and the evolution during thermal annealing after growth. By in-situ synchrotron X-ray diffraction and reflection measurements, specifically, the development of the preferred orientation of the grains, the lattice constant (stress), the grain size, and the microstrain were studied during and after growth. The parts of the studies which include the development of the Au(111) diffraction peak intensity, the grain size, the microstrain and the lattice constant have been published [2], while the systematic experimental investigation of the evolution of the texture during growth and during subsequent thermal annealing is reported in the present paper.

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EXPERIMENTAL The deposition chamber [3] was mounted