Frequency-resolved Raman for transient thermal probing and thermal diffusivity measurement.

A new transient Raman thermal probing technique, frequency-resolved Raman (FR-Raman), is developed for probing the transient thermal response of materials and measuring their thermal diffusivity. The FR-Raman uses an amplitude-modulated square-wave laser for simultaneous material heating and Raman excitation. The evolution profile of Raman properties: intensity, Raman wavenumber, and emission, against frequency are reconstructed and used for fitting to determine the thermal diffusivity. A microscale silicon (Si) cantilever is used to investigate the capacity of this new technique. The thermal diffusivity is determined as 9.57×10^-5  m²/s, 11.00×10^-5  m²/s, and 9.02×10^-5  m²/s via fitting Raman intensity, wavenumber, and total Raman emission, respectively. The results agree well with literature data. The FR-Raman provides a novel way for transient thermal probing with very high temporal resolution and micrometer-scale spatial resolution.