A novel nano-scale non-contact temperature measurement technique for crystalline materials

Abstract

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 conventional scanning thermal microscopy, which uses contact probes, ThSEM is a non-contact method. In contrast to optical temperature mapping techniques, ThSEM does not have the spatial resolution limitation that arises from the optical wavelength and theoretically can reach a resolution of <10 nm. The hardware setup is very similar to the EBSD system in an SEM, which can make the integration of temperature mapping 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 depending on the specific SEM capability. This technique thus adds a new channel-the temperature signal-to the collection of existing SEM signals.

New Methods for Measuring Chemistry and Temperature Using Scanning Ion and Electron Beams

“…Figure 2 shows the result of intensity traces across a (400) Kikuchi line in an EBSD pattern recorded from a Si(001) sample with 20 keV electrons in a JEOL 840 SEM [5]. As expected, the intensity of the excess Kikuchi line decreases monotonically with increasing temperature, while the intensity of diffuse scattering increases.…”

“…The spatial resolution we have estimated from the 20 keV beam used for these experiments is c. 80 nm; employing finely focused low energy electron beams in a state-of-the-art field emission instrument should enable 10 nm resolution to be attained. We estimate the temperature sensitivity from our measurements to be [5][6][7][8][9][10] o C. Most importantly, while other techniques such as scanning thermal microscopy have comparable spatial resolution and nominally better temperature sensitivity, the over-arching advantage of the current technique is that is essentially non-contact. This is a crucial advantage in making temperature measurements of nanoscale objects, such that the act of measurement itself does not substantially modify the local temperature.…”

Temperature dependence of secondary electron emission: A new route to nanoscale temperature measurement using scanning electron microscopy

“…In such samples, several material parameters change with temperature which could plausibly contribute to a change in SE emission, such as the work function, [16][17][18] electronic bandgap, 19 and populations of phonons which can scatter SEs, although identifying and elucidating the specific mechanism(s) is beyond the scope of this study. 20 TEM bright field images 8 and SEM EBSD patterns 9 are also known to depend weakly on temperature due to thermal diffuse scattering (the Debye-Waller effect), which can also be understood as temperature-dependent electron scattering.…”

“…A similar thermal-diffuse scattering mechanism has shown β ∼ 10 −4 K −1 in the electron backscatter diffraction (EBSD) pattern in an SEM. 9 In contrast to those more specialized imaging modes, SEM using secondary electrons (SEs) is the most commonly used imaging mode but has not previously been applied to measure temperature. Although not performed in an SEM, several past studies using electron beams have reported small temperature effects on SE yield in Ge, 10 MgO, 11 and four magnetic metals.…”

Multichannel fiber Bragg grating for temperature field monitoring

“…In order to precisely map the physical parameters and gradients, the spatial resolution of the temperature sensor has to be as high as possible. There are two main temperature field mapping methods in use which can achieve a spatial resolution of less than a millimeter: thermometry based on nuclear magnetic resonance (NMR) [1] and electron backscatter diffraction [4]. However, they are not suitable for in situ measurement in many applications due to their large size and electromagnetic interference.…”