Robust and high-sensitivity thermal probing at the nanoscale based on resonance Raman ratio (R3)

Abstract

Raman spectroscopy-based temperature sensing usually tracks the change of Raman wavenumber, linewidth and intensity, and has found very broad applications in characterizing the energy and charge transport in nanomaterials over the last decade. The temperature coefficients of these Raman properties are highly material-dependent, and are subjected to local optical scattering influence. As a result, Raman-based temperature sensing usually suffers quite large uncertainties and has low sensitivity. Here, a novel method based on dual resonance Raman phenomenon is developed to precisely measure the absolute temperature rise of nanomaterial (nm WS2 film in this work) from 170 to 470 K. A 532 nm laser (2.33 eV photon energy) is used to conduct the Raman experiment. Its photon energy is very close to the excitonic transition energy of WS2 at temperatures close to room temperature. A parameter, termed resonance Raman ratio (R3) Ω=IA1g /IE2g is introduced to combine the temperature effects on resonance Raman scattering for the A1g and E2g modes. Ω has a change of more than two orders of magnitude from 177 to 477 K, and such change is independent of film thickness and local optical scattering. It is shown that when Ω is varied by 1%, the temperature probing sensitivity is 0.42 K and 1.16 K at low and high temperatures, respectively. Based on Ω, the in-plane thermal conductivity (k) of a ~25 nm-thick suspended WS2 film is measured using our energy transport state-resolved Raman (ET-Raman). k is found decreasing from 50.0 to 20.0 Wm-1K-1 when temperature increases from 170 to 470 K. This agrees with previous experimental and theoretical results and the measurement data using our FET-Raman. The R3 technique provides a very robust and high-sensitivity method for temperature probing of nanomaterials and will have broad applications in nanoscale thermal transport characterization, non-destructive evaluation, and manufacturing monitoring.

A review on current development of thermophotovoltaic technology in heat recovery

“…Metamaterial, especially photonic crystals, as a research hotspot in recent years, have a promising future in the preparation of TPV emitters [90][91][92][93][94][95]. Its precise geometry and dimensions are smaller than the wavelength at which it acts, thus allowing it to exert its influence on the wave [96][97][98][99]. Therefore, the emission spectrum can be precisely tuned by adjusting the microstructure of the metamaterial [100][101][102].…”

A brief review on the recent development of phonon engineering and manipulation at nanoscales

“…On the experimental side, advances in thermometry, such as the 3ω method [33,34], T-type method [35,36], H-type method [37,38], Raman thermometry [39][40][41][42][43][44][45][46], time-domain and frequency-domain thermoreflectance (TDTR and FDTR) [4,[47][48][49][50][51][52][53], have enabled the characterization of heat transport processes and thermal properties on smaller spatial and temporal scales. Raman thermometry is a non-contact optical temperature measurement technology that utilizes Raman scattering.…”

Perspectives on Energy Transport at the Micro/Nanoscale

“…Energy transport at the micro/nanoscale is still a very active research area, and current research is very diverse, including study of detailed phonon dynamics, structure, and behaviors, material design to either enhance or suppress energy transport, and new technology development to overcome challenges in characterizing special materials [29,30].…”