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Title: Compressive intrinsic stress originates in the grain boundaries of dense refractory polycrystalline thin films

Intrinsic stresses in vapor deposited thin films have been a topic of considerable scientific and technological interest owing to their importance for functionality and performance of thin film devices. The origin of compressive stresses typically observed during deposition of polycrystalline metal films at conditions that result in high atomic mobility has been under debate in the literature in the course of the past decades. In this study, we contribute towards resolving this debate by investigating the grain size dependence of compressive stress magnitude in dense polycrystalline Mo films grown by magnetron sputtering. Although Mo is a refractory metal and hence exhibits an intrinsically low mobility, low energy ion bombardment is used during growth to enhance atomic mobility and densify the grain boundaries. Concurrently, the lateral grain size is controlled by using appropriate seed layers on which Mo films are grown epitaxially. The combination of in situ stress monitoring with ex situ microstructural characterization reveals a strong, seemingly linear, increase of the compressive stress magnitude on the inverse grain size and thus provides evidence that compressive stress is generated in the grain boundaries of the film. These results are consistent with models suggesting that compressive stresses in metallic films deposited atmore » high homologous temperatures are generated by atom incorporation into and densification of grain boundaries. However, the underlying mechanisms for grain boundary densification might be different from those in the present study where atomic mobility is intrinsically low.« less
Authors:
;  [1] ; ;  [2] ; ;  [3]
  1. Nanoscale Engineering Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)
  2. Institut P', Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, SP2MI, Téléport 2, Bd M. et P. Curie, F-86962 Chasseneuil-Futuroscope (France)
  3. Plasma and Coatings Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)
Publication Date:
OSTI Identifier:
22494986
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 119; Journal Issue: 5; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DEPOSITION; EPITAXY; GRAIN BOUNDARIES; GRAIN SIZE; MOBILITY; POLYCRYSTALS; REFRACTORY METALS; SPUTTERING; STRESSES; THIN FILMS; VAPOR DEPOSITED COATINGS