Ultra-high resolution steady-state micro-thermometry using a bipolar direct current reversal technique

Abstract

The suspended micro-thermometry measurement technique is one of the most prominent methods for probing the in-plane thermal conductance of low dimensional materials, where a suspended microdevice containing two built-in platinum resistors that serve as both heater and thermometer is used to measure the temperature and heat flow across a sample. The presence of temperature fluctuations in the sample chamber and background thermal conductance through the device, residual gases, and radiation are dominant sources of error when the sample thermal conductance is comparable to or smaller than the background thermal conductance, on the order of 300 pW/K at room temperature. In this work, we present a high resolution thermal conductance measurement scheme in which a bipolar direct current reversal technique is adopted to replace the lock-in technique. We have demonstrated temperature resolution of 1.0–2.6 mK and thermal conductance resolution of 1.7–26 pW/K over a temperature range of 30–375 K. The background thermal conductance of the suspended microdevice is determined accurately by our method and allows for straightforward isolation of this parasitic signal. This simple and high-throughput measurement technique yields an order of magnitude improvement in resolution over similarly configured lock-in amplifier techniques, allowing for more accurate investigation of fundamental phonon transport mechanisms in individual nanomaterials.

Enabling Oxidation Protection and Carrier-Type Switching for Bismuth Telluride Nanoribbons via in Situ Organic Molecule Coating

“…The thermoelectric figure of merit zT = [ S 2 σ/(κ lattice + κ electronic ) ] T is more challenging to compare, but we begin by calculating the total thermal conductivity (κ total ) of the uncoated Bi 2 Te 3 nanoribbon following an established bipolar direct current reversal technique and then determined the electronic contribution via the Wiedemann–Franz law κ electronic = σ LT : κ total = κ lattice + κ electronic = κ lattice + σ L T κ lattice = κ total − σ L T where T is the absolute temperature, L is the Lorenz number, κ lattice is the lattice contribution to the thermal conductivity, and κ electronic is the electronic contribution to the thermal conductivity. To assess the validity of our κ electronic calculation and allow us to better quantify the uncertainty in zT , we use three different methods for calculating L (each based on somewhat different assumptions).…”