Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 4: Mechanical Properties I

MM 4.2: Talk

Monday, March 26, 2012, 10:30–10:45, H 0106

Strain Relaxation Kinetics in Thin Nano-Crystalline Platinum Films — •Wolfgang Gruber¹, Carsten Baehtz², Christian Kübel³, Wolfram Leitenberger⁴, and Harald Schmidt¹ — ¹TU Clausthal, Institut für Metallurgie — ²Helmholtz Zentrum Dresden Rossendorf, Institute of Ion Beam Physics and Materials Research — ³Karlsruher Institut für Technologie, Karlsruher Micro Nano Facility — ⁴Universität Potsdam, Institut für Physik und Astronomie

Thin metal films with a thickness in the nanometer to the micrometer range are important for various areas of science and technology. Residual stresses, which are commonly assumed to be bi-axial in thin films, result from different thermal expansion coefficients of substrate and film (thermal stress) and/or from stress formation during film deposition (grown-in stress). During isothermal annealing, residual stresses relax as a function of annealing time and temperature. We used thin nano-crystalline Pt films deposited on oxidized silicon wafers to investigate the role of vacancies for relaxation of strain resulting from compressive stress. We applied a method which is based on the fundamental concept of dilatometry. We modified this basic concept and used synchrotron based combined in-situ X-ray diffractometry and reflectometry. From the experimentally determined relative changes of the lattice parameter and of the film thickness the modification of vacancy concentration and residual strain was derived as a function of annealing time. The results indicate that relaxation of strain is accompanied by the creation of vacancies at the free film surface [1].

[1] W. Gruber et al., Phys. Rev. Lett., in print.