In situ time-domain thermoreflectance measurements using Au as the transducer during electrolyte gating

Abstract

Understanding the relationships between the thermal conductivity and carrier density in thin films is of great importance for the thermal management of flexible thin film electronics. Here, we report a robust measurement technique to tune the carrier density in thin films and to evaluate their cross-plane thermal conductivities simultaneously. We employed the time-domain thermoreflectance method using an Au transducer and evaluated the thin film thermal conductivity in situ using electrolyte gating with an ionic gel. The robust measurement technique proposed in this study elucidated the relationships among the above-mentioned parameters in semiconducting single-walled carbon nanotubes.

Heat and Charge Carrier Flow through Single-Walled Carbon Nanotube Films in Vertical Electrolyte-Gated Transistors: Implications for Thermoelectric Energy Conversion

“…The carrier density that can be injected is the same as that of a conventionally horizontal electrolyte-gated transistor. In our previous study, the out-of-plane thermal conductivity also remained the same as the carrier density increased to 10 19 cm –3 . Such constant behavior of κ has also been observed in other materials such as amorphous indium–gallium–zinc oxide film .…”

“…In our previous study, the out-of-plane thermal conductivity also remained the same as the carrier density increased to 10 19 cm −3 . 15 Such constant behavior of κ has also been observed in other materials such as amorphous indium−gallium−zinc oxide film. 22 The thermal conductivity of an amorphous indium−gallium−zinc oxide film also shows a constant value when its carrier density is below 10 20 cm −3 .…”

“…In particular, in our developed TDTR system, we employ electrochemically stable Au as a metal transducer, and thus, we can evaluate both electrical and thermal characteristics in the same sample at the same time. Recently, we employed the Au-TDTR system in semiconducting single-walled carbon nanotube (SWCNT) films, evaluated the thermal conductivity in situ during electrolyte gating, and clarified the relationships between the out-of-plane thermal conductivity and the Fermi-level location of the semiconducting SWCNTs . In this previous study, we discussed the relationships between the out-of-plane thermal conductivity and in-plane electrical conductivity.…”

“…Recently, we employed the Au-TDTR system in semiconducting single-walled carbon nanotube (SWCNT) films, evaluated the thermal conductivity in situ during electrolyte gating, and clarified the relationships between the out-of-plane thermal conductivity and the Fermi-level location of the semiconducting SWCNTs. 15 In this previous study, we discussed the relationships between the out-of-plane thermal conductivity and in-plane electrical conductivity. Hence, the directions between the heat and electrical currents were not the same.…”

Control of Thermal Conductance across Vertically Stacked Two-Dimensional van der Waals Materials via Interfacial Engineering

“…Here, considered parameters are volumetric heat capacity C , thermal diffusivity α, thermal conductivity κ (κ = C × α), thermal conductance G , and thermal effusivity b . The sensitivity of a labeled parameter p , S p , is defined as follows where φ is the phase signal in a lock-in amplifier.…”