A novel contactless technique for thermal field mapping and thermal conductivity determination: Two-Laser Raman Thermometry

Abstract

We present a novel high resolution contactless technique for thermal conductivity determination and thermal field mapping based on creating a thermal distribution of phonons using a heating laser, while a second laser probes the local temperature through the spectral position of a Raman active mode. The spatial resolution can be as small as 300 nm, whereas its temperature accuracy is ±2 K. We validate this technique investigating the thermal properties of three free-standing single crystalline Si membranes with thickness of 250, 1000, and 2000 nm. We show that for 2-dimensional materials such as free-standing membranes or thin films, and for small temperature gradients, the thermal field decays as T (r) ∝ ln(r) in the diffusive limit. The case of large temperature gradients within the membranes leads to an exponential decay of the thermal field, T ∝ exp[−A · ln(r)]. The results demonstrate the full potential of this new contactless method for quantitative determination of thermal properties. The range of materials to which this method is applicable reaches far beyond the here demonstrated case of Si, as the only requirement is the presence of a Raman active mode. 74.25.nd, 66.30.Xj,

Phonon thermal conduction in novel 2D materials

“…The primary challenge lies in the difficulties in measuring the thermal contact resistance and the detecting temperature distribution in micro/nano scale with high sensitivity, although recent advances and modified experimental techniques claimed to have partially solved these problems [79,80]. The second problem is related to the physics behind the novel thermal conduction including mode contributions, electron-phonon coupling on the contact, phonon-phonon scatterings in 2D sheet with size approach few hundred micrometers and above [189,190].…”

“…As we know, in electrical transport measurements, the four probe method is used to reduce the effect from the contact resistance. Analogous to electrical measurement, two-laser Raman thermometry method was invented to measure intrinsic thermal conduction in silicon film [79]. In this method, Reparaz et al used one laser beam focused on the center of sample to create a thermal gradient, and mapped the temperature distribution using another laser from Raman spectroscope (Figure 4a).…”

Nanoscale thermal imaging of dissipation in quantum systems

“…Despite its vital importance the microscopic behavior of a system is usually not formulated in terms of dissipation because the latter is not a readily measureable quantity on the microscale. Although nanoscale thermometry is gaining much recent interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] , the existing thermal imaging methods lack the necessary sensitivity and are unsuitable for low temperature operation required for study of quantum systems. Here we report a superconducting quantum interference nano-thermometer device with sub 50 nm diameter that resides at the apex of a sharp pipette and provides scanning cryogenic thermal sensing with four orders of magnitude improved thermal sensitivity of below 1 µK/Hz 1/2 .…”

Thermal conductivity of ultrathin nano-crystalline diamond films determined by Raman thermography assisted by silicon nanowires

“…For measuring temperatures, Raman thermography was used in the fabricated structures, this has been successfully tested for similar purposes elsewhere. 6,[30][31][32][33] A Renishaw InVia Raman system with a Raman shift resolution better than 0.1 cm À1 was employed, using a 488 nm Ar-ion laser line focused with an 0.65 N.A. 50Â objective onto a spot size smaller than 1 lm.…”