Temperature Profiles and Heat Conduction in Individual Suspended 1D and 2D Nanostructures by Scanning Thermal Microscopy

We present a novel combined setup, involving a Scanning Thermal Microscope [1] (SThM) embedded in a Scanning Electron Microscope (SEM) specifically designed for highly-controlled investigation of individual nanostructures by means of a self-heated SThM resistive probe. The instrument is demonstrated through the characterization of thermal conductance profile along a suspended nanowire integrated in a microfabricated device, manufactured by the department of advanced energy materials of the Catalonia Institute for Energy Research. This allows determining its heat-transport property without relying only on the heat flow as in electrothermal devices and exhibits a potential spatial resolution well beyond that of Raman thermometry. Heat conduction within a room-temperature rough silicon nanowire was analyzed. The rough nature of the nanowire surface, which prohibits the use of vacuum-SThM due to lose contact for heat dissipation, was circumvented by decorating the wire with periodic platinum dots. Reproducible approaches over these dots, enabled by the live feedback image provided by the SEM, yielded a strong improvement in thermal contact resistance and a higher accuracy in its estimation. The results – thermal resistance at the tip-sample contact of 188 ±3.7 K/W and equivalent axial thermal conductivity of the nanowire of 13.7 ±1.6 W/mK – are obtained by performing a series of approach curves on the dots [2].
Conventional SThM experiments in the jump-in contact mode and using a self-heated SThM resistive probe may also allow measuring heat conduction within nanostructures such as 2D materials. Using this approach we characterize suspended 2D samples made of single and multilayer hBN clamped between two microfabricated platforms at different temperatures, allowing to generate a temperature distribution in the device. Thermal conductance and temperature along the nanomaterials excited in various electrothermal regimes are evaluated and compared with those obtained using Raman spectroscopy measurements [3].
These results demonstrate that SThM is a powerful tool for thermal investigation at the submicronscale.

[1] S. Gomès et al., Phys. Status Solidi A, 212 (2015), 477–494.
[2] J. M. Sojo Gordillo et al., Small, 2305831 (2024)
[3] C. Brochard, Doctoral dissertation, Université Paris-Saclay, 2023.