Universal scaling and measurability limits of thermal-conductivity measurement by a nanoscale point contact
Abstract
Thermal conductivity (κ) measurement of a thin film is critical for developing thermal management materials in heterogeneous systems. A nanoscale point contact method based on scanning thermal microscopy (SThM) offers a unique approach to probe κ with nanoscale spatial resolution in sub-100 nm thick films. Extracting κ of a thin film from this method requires separating film, substrate, and interface contributions that are comparable in magnitude. Multiple unknowns make this extraction a high dimensional problem. In this work, we used dimensional analysis to reduce the number of variables to provide physical insights into the realistic bounds of κ measurement. We show that the total tip-sample thermal resistance Rss, originally a function of six variables, reduces to four independent dimensionless groups. These groups are used to construct a mathematical relation that captures the dependence of Rss on the governing parameters. The resulting analysis shows that the point contact tip-film-substrate problem is governed by a single dimensionless invariant, Ω= Rssκsubt, and two control parameters: the confinement ratio t/b and the thermal contrast κsub/κfilm. From the invariant, we derive an amplification factor, set only by the contact geometry and the interfaces, that converts the uncertainty of a measurement into an uncertainty in the extracted conductivity. This factor scales with the ratio of the parasitic interface resistance to the film's sheet thermal resistance and bounds the film conductivity that a given contact can resolve. We apply the framework to a 14±1 nm Al film grown on SiO2 to locate the measurement within the established bound. The framework then lets us map its thermal resistance with sub-100 nm spatial resolution and recover the local thermal conductivity.
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BibTeX
@misc{munde2026universal,
title = {{Universal scaling and measurability limits of thermal-conductivity measurement by a nanoscale point contact}},
author = {Ram Munde and Raisul Islam},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.24846},
eprint = {2610.24846},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.24846},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Universal scaling and measurability limits of thermal-conductivity measurement by a nanoscale point contact
AU - Ram Munde
AU - Raisul Islam
PY - 2026
DA - 2026/10/17
PB - arXiv
DO - 10.48550/arxiv.2610.24846
UR - https://arxiv.org/abs/2610.24846
AB - Thermal conductivity (κ) measurement of a thin film is critical for developing thermal management materials in heterogeneous systems. A nanoscale point contact method based on scanning thermal microscopy (SThM) offers a unique approach to probe κ with nanoscale spatial resolution in sub-100 nm thick films. Extracting κ of a thin film from this method requires separating film, substrate, and interface contributions that are comparable in magnitude. Multiple unknowns make this extraction a high dimensional problem. In this work, we used dimensional analysis to reduce the number of variables to provide physical insights into the realistic bounds of κ measurement. We show that the total tip-sample thermal resistance R_ss, originally a function of six variables, reduces to four independent dimensionless groups. These groups are used to construct a mathematical relation that captures the dependence of R_ss on the governing parameters. The resulting analysis shows that the point contact tip-film-substrate problem is governed by a single dimensionless invariant, Ω= R_ssκ_subt, and two control parameters: the confinement ratio t/b and the thermal contrast κ_sub/κ_film. From the invariant, we derive an amplification factor, set only by the contact geometry and the interfaces, that converts the uncertainty of a measurement into an uncertainty in the extracted conductivity. This factor scales with the ratio of the parasitic interface resistance to the film's sheet thermal resistance and bounds the film conductivity that a given contact can resolve. We apply the framework to a 14±1 nm Al film grown on SiO_2 to locate the measurement within the established bound. The framework then lets us map its thermal resistance with sub-100 nm spatial resolution and recover the local thermal conductivity.
ER -