Multilayered film stacks, with length scales less than 10 nm are commonly used in
a variety of devices, but present significant challenges to mechanical testing
and evaluation. This is due to property convolution of the different layers.
Both the properties of the individual layers and the combined response of the
film stack are important input for design optimization. Here, we present
ex-situ nanoindentation of a film stack representative of a
perpendicular magnetic recording (PMR) hard disc drive (HDD), with more than 10
layers. We then compare this with in-situ transmission electron
microscopy indentation to visualize deformation of individual layers of the
stack. The ex-situ testing reveals early plastic deformation,
with an initially high contact pressure (13 GPa) and modulus ( >160
GPa), followed by significant softening (8 GPa contact pressure and 140 GPa
modulus), then slight hardening to 9 GPa. From in-situ testing,
it is revealed that the metallic layer directly under the diamond like carbon
(DLC) contributes the majority of the deformation and plastic flow, which is in
turn constrained by a metallic oxide.