Instrumented indentation is a widely used technique to study the mechanical behavior of materials at small length scales and thus has been exploited in particular for metals, ceramics, glasses, and polymers. Mechanical tests of bulk materials, microscopic and spectroscopic studies may be conducted to complement indentation and enable the determination of the kinetics and physics involved in the mechanical deformation of materials at the crystallographic and molecular level, e.g. strain build-up in crystal lattices, phase transformations, and changes in crystallinity or orientation. However, many of these phenomena occurring during indentation can only be observed in their entirety and analyzed in depth under in situ conditions. This paper describes the design, calibration, and operation of an indentation device that is coupled with a Raman microscope to conduct in situ spectroscopic and optical analysis of mechanically deformed regions under contact loading. The open-loop controlled force transducer of the device allows adjustment of crucial experimental parameters, such as indentation strains and strain rates. An incorporated displacement sensor provides for displacement measurements, and the measurement of force-displacement curves comparable to conventional instrumented indentation instruments. The device is designed to mount on the sample stage of an inverted optical microscope that is configured for Raman microscopy, which allows optical access to the mechanically deformed regions of transparent samples. The capabilities of the presented device are demonstrated by in situ studies of the indentation-induced phase transformations of Si thin films and modifications of molecular conformations in high density polyethylene films.
Citation: Review of Scientific Instruments
Pub Type: Journals
indentation, Raman microprobing, in situ analysis