Thermal conductivity tuning of scalable nanopatterned silicon membranes measured with a three-probe method

TL;DR

This study demonstrates scalable nanopatterned silicon membranes with tunable thermal conductivity, employing a novel three-probe measurement technique to accurately characterize thermal properties despite contact resistances.

Contribution

It introduces a scalable fabrication method for nanopatterned silicon membranes and extends the three-probe technique for precise thermal conductivity measurement in nanostructures.

Findings

Achieved a fivefold reduction in thermal conductivity to 7.3 W/m.K.

Validated the measurement method on unpatterned silicon films with 46.5 W/m.K at room temperature.

Controlled hole etching effectively tunes thermal transport across temperatures.

Abstract

Phononic silicon structures have emerged as an integrable and scalable nanosystem for tailoring thermal transport. However, their widespread adoption has been limited by their complex fabrication pathways. Alongside, the reliable characterization of thermal properties in suspended nanostructured films remains challenging, as thermal contact resistances often hinder the accuracy of measurements. In this work, we demonstrate a clear and controllable reduction of thermal conductivity in nanopatterned silicon membranes. A block copolymer self-assembly approach is employed to fabricate nanoholed silicon films with a pitch of 63 nm and hole diameters of 35 nm. Additionally, we introduce an extension of the three-probe technique that enables robust, quantitative, and spatially resolved thermal conductivity measurements in complex thin-film systems, accounting for thermal contact artifacts. The method is validated through measurements on unpatterned 40 nm-thick silicon thin films between 30 and 350 K, yielding a room-temperature thermal conductivity of 46.5 W/m.K. Finally, we further show that controlled etching of the nanoholes provides a powerful means to tune thermal transport in the overall studied temperature range, establishing hole etch depth control as an effective parameter in phononic silicon. Specifically, a fivefold reduction in thermal conductivity is achieved, reaching 7.3 W/m.K for fully etched-through membranes at room temperature.