Dresden 2026 – scientific programme
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DS: Fachverband Dünne Schichten
DS 13: Layer Properties
DS 13.2: Talk
Wednesday, March 11, 2026, 15:30–15:45, REC/B214
Mechanical Stress Evolution in Polycrystalline Ge Thin Films under MeV Ion Irradiation — •Karla J. Paz Corrales1, Aaron Reupert2, Kevin Lubig2, Frank A. Müller2, Berit Marx-Glowna3, Ralf Röhlsberger3, Till Weickhardt1, Giancarlo Soavi1, Martin Hafermann1, Elke Wendler1, and Carsten Ronning1 — 1Institute of Solid State Physics, Friedrich Schiller University Jena, 07743 Jena, Germany — 2Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, 07743 Jena, Germany — 3Helmholtz-Institut Jena, Fraunhoferstr. 8, 07743 Jena, Germany
Polycrystalline Ge thin films were deposited by magnetron sputtering, annealed at 600 °C for 1 h, and irradiated with 1.8 MeV Au ions over a broad fluence range. Structural, optical, and in-situ mechanical stress analyses were performed to investigate irradiation-induced property modifications. At low fluences, the films show a reduction of the initial tensile residual stress from the preparation process. This stress compensation is linked to the formation of point defects, which also decrease the optical band gap. These defects can migrate to grain boundaries, where recombination enhances the resistance to amorphization compared with single-crystalline Ge. At higher fluences, defect accumulation increases tensile stress and leads to the formation of mixed polycrystalline-amorphous phases. With further irradiation, the films fully transform into an amorphous phase, as evidenced by changes in both structural and optical properties. In this amorphous state, additional stress relaxation occurs, attributed to plastic flow or to interface effects between the film and substrate.
Keywords: ion irradiation; mechanical stress; germanium; optical properties