Sample pattern and temperature distribution in nanocalorimetry measurements
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Uniform temperature distribution over the probed area of nanocalorimeters is critical for accurate measurements and is often assumed, but the temperature distribution is, in many cases, non-uniform, depends on the sample dimensions and coverage, and can affect the measurement results. Here, using an aluminum thin film as a model material, the effects of sample coverage on measured melting temperature and enthalpy of fusion were studied. Results suggest that undersized samples increase the reported peak and onset values for melting temperature, and that oversized samples cause significant errors in the quantification of the enthalpy of fusion. A finite element model of the dynamics of the temperature distribution was created to clarify the underlying mechanisms. This work provides a simple guideline for the ideal sample pattern for chip-based thermal measurements: covering the entire probed area of the heater: not undersized or oversized.
KeywordsNanocalorimeter Nanocalorimetry Fast scanning calorimetry Temperature distribution Melting temperature Aluminum Finite element
Certain commercial equipment, instruments, software, and materials are identified in this document. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products identified are necessarily the best available for the purpose. Nanocalorimeter fabrication was performed in part at the NIST Center for Nanoscale Science & Technology (CNST). Richard Chen was a summer intern from Montgomery Blair High School.
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