Temperature measurement by thermal diffuse scattering in electron backscatter diffraction

Abstract

Temperature measurement is important to studies of heat generation and transfer processes in a wide range of engineering systems. However, the feature sizes of many engineering systems, such as microelectronic, optoelectronic, and micromechanical systems, have been reduced down to length scales as small as tens of nanometers and continue to decrease. Experimental studies of the nano-scale thermal processes involved in such systems are not possible without high spatial resolution temperature measurement techniques.

In this thesis, a new high spatial resolution non-contact temperature measurement technique (thermal scanning electron microscopy, ThSEM) is demonstrated. It employs temperature dependent thermal diffuse scattering in electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). Unlike scanning probe based techniques, which uses contacting probes, ThSEM is a non-contact method. In contrast to optical techniques, ThSEM does not have the spatial resolution limitation that arises from the optical wavelength. The hardware setup is very similar to the EBSD system in an SEM, which can make the integration of temperature measurement into an SEM relatively straightforward. Moreover, multiple signals or contrast mechanisms, such as temperature distributions, grain orientation maps, topographic images and elemental maps can be obtained from the same sample area simultaneously depending on the specific SEM capability. This technique thus adds a new channel - the temperature signal - to the collection of existing SEM signals.

There are basically three categories of such existing techniques - scanning probe based techniques, optical techniques, and thin coating methods. However, none of them adequately combines high spatial resolution and non-perturbing measurement capabilities which are critical to the experimental studies of these nano-scale thermal processes.