Sputtering of rough and structured tungsten surfaces: An overview on experimental, numerical, and analytical approaches and recent results

Wall Forum

  • Datum: 30.11.2022
  • Uhrzeit: 15:30 - 16:30
  • Vortragender: Christian Cupak
  • TU Wien
  • Ort: Seminarraum D3 / Zoom
  • Gastgeber: IPP
Surface roughness is known for many years to affect the sputtering behaviour of materials under ion bombardment [1]. While theoretical models and simulation codes are often approximating surfaces to be perfectly flat, applications in technology, especially for first wall materials in nuclear fusion devices, may require a more detailed consideration of the roughness.In recent years, the question arose whether an accessible surface roughness parameter exists which allows to describe (static) effects on sputtering yields for conventionally rough surfaces. Well-known parameters like the root-mean-square roughness failed to describe the trends, but it was observed that the mean value of the surface inclination angle distribution enables a scale-independent characterisation, even allowing to predict effective sputtering yields without need for detailed simulations or experiments [2]. Understanding these geometric effects from surface topography on the sputtering yield of conventionally rough surfaces, it was possible to optimise tungsten surfaces by implementing nanocolumnar structures, thereby achieving very low sputtering yields, e.g., as desired for first wall applications in nuclear fusion devices [3]. In this talk, an overview on the experimental methods (quartz crystal microbalance), numerical simulation techniques (SPRAY) and analytical models (roughness parameters for sputter yield prediction), which were developed in Vienna to investigate structured surfaces under ion bombardment, is given. Furthermore, a comparison of the characteristic sputtering behaviour of flat, conventionally rough [2] and oriented nanocolumnar tungsten surfaces [3] will be presented during this talk, also indicating the relevance and potential for application in nuclear fusion devices.[1] M. Küstner et al., Nucl. Instrum. Methods Phys. Res. B, 145 (1998), 320-331[2] C. Cupak, et al., Appl. Surf. Sci. 570 (2021) 151204[3] A. Lopez-Cazalilla, C. Cupak, et al., Phys. Rev. Mat. 6 (2022) 075402

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