Investigation of the fracture of very thin amorphous alumina film during spherical nanoindentation

Thin amorphous alumina layers (10 to 40nm thick) are processed on sputtered aluminum thin film (500nm) by atomic layer deposition (ALD) at low temperature (85°C). Global methodology combining quantitative experimental observations of fracture and numerical modeling is proposed to obtain the fracture...

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Bibliographic Details
Published in:Thin solid films 2017-09, Vol.638, p.34-47
Main Authors: Mercier, David, Mandrillon, Vincent, Parry, Guillaume, Verdier, Marc, Estevez, Rafael, Bréchet, Yves, Maindron, Tony
Format: Article
Language:English
Subjects:
ALD alumina
Cracks
Finite element modeling
Fracture strength
Mechanics
Mechanics of materials
Nanoindentation
Physics
Pop-in
Thin hard film
Weibull statistical analysis
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Summary:Thin amorphous alumina layers (10 to 40nm thick) are processed on sputtered aluminum thin film (500nm) by atomic layer deposition (ALD) at low temperature (85°C). Global methodology combining quantitative experimental observations of fracture and numerical modeling is proposed to obtain the fracture strength of ALD thin film on Al layer. First, mechanical properties of the multilayer specimen are characterized by Berkovich nanoindentation, then fracture of ALD alumina is studied through spherical indentation with various tip radius. Spherical indentation load driven-displacement curves display a plateau (pop-in) at a critical load and critical indentation depth. A statistical approach is used to determine pertinent/fracture parameters from pop-in displacement. Careful SEM and AFM observations of indentation imprint exhibit circumferential cracking in agreement with the assumption that the pop-in event is predominantly controlled by the fracture of the oxide layer on the soft Al film. Finally, a numerical model calibrated with experimental results is used in order to predict both the mechanical response prior to the oxide fracture and a value of fracture strength for ALD alumina thin films. •Fracture of thin hard film on soft layer is investigated by nanoindentation.•Good correlation between pop-in event and fracture of thin hard film is observed.•Statistical analysis of the fracture event and cracks morphologies are presented.•Fracture stress is assessed by analytical and numerical modeling.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2017.07.040