In-Situ SPM Imaging: An Overview

All of Hysitron's nanomechanical testing platforms are capable of in-situ Scanning Probe Microscopy (SPM) imaging. This technique provides high-resolution SPM images at the location of the test by imaging with the same probe that performs the nanomechanical testing. This provides fundamental information regarding the surface topography of the test location and the resulting test deformation which would be unavailable without the image resolution offered by in-situ imaging. Hysitron's probe-scanning system allows imaging of any location on large samples or imaging of multiple samples without necessitating user intervention.

Probe Placement

Precise positioning of the indentation probe is required in order to obtain reliable and repeatable data from nanomechanical test. In-situ imaging is an indispensable technique for determining that the probe is placed at the desired location on the sample. With in-situ imaging it is possible to position the indenter probe with better than ten-nanometer resolution. This is particularly useful in interfacial studies or in testing nonhomogeneous samples such as multiphase materials. Witout the information provided by in-situ imaging, the user cannot be guaranteed that the test is placed within the desired region. Even homogenous materials typically pssess features such as surface roughness that must be avoided in order to eliminate testing anomalies. In-situ SPM imaging facilitates precise positioning of the probe for the most accurate test results possible.

Imaging of Deformation

In-situ imaging can provide a wealth of information concerning the results of a test. When coupled with the correponding load-displacement data, in-situ imaging can give insight into the deformation incurred during the test. Material property measurements, such as those for fracture toughness and yield strength, rely on information that can only be obtained from images that possess the resolution that this method can provide. While subsequent ex-situ SPM imaging could provide similar information, it is difficult and time-consuming to locate the site of the test. Also, deformation created in some materials, such as viscoelastic materials, recovers with time. In these cases the time elasped betweed testing and imaging must be minimized. With in-situ imaging it is possible to acquire images seconds after completing a test, offering the most accurate representation of the real deformation. Further, with repeated imaging of the test location, the recovery process can be documented. Observation of the mode and extent of recovery can provide the information necessary for future product development.