Concurrent thermal conductivity measurement and internal structure observation of individual one-dimensional materials using scanning transmission electron microscopy

Abstract

The thermal conductivity of individual nanomaterials can vary from sample to sample due to the difference in the geometries and internal structures, and thus concurrent structure observation and thermal conductivity measurement at the nanoscale is highly desired but challenging. Here, we have developed an experimental method that allows concurrently the in-situ thermal conductivity measurement and the real-time internal structure observation of a single one-dimensional (1D) material using scanning transmission electron microscopy in a scanning electron microscope (STEM-in-SEM).In this method, the two ends of the 1D nanomaterial are bonded on a tungsten probe and a suspended platinum nanofilm, respectively. The platinum nanofilm serves simultaneously as a heater and a resistance thermometer, ensuring highly sensitive thermal measurements. The platinum nanofilm is fabricated on the edge of the silicon wafer so that the electron beam can transmit through the 1D material and be detected by the STEM detector, which caters for real-time observation of the inner nanostructure.Using this method, we in-situ measured the thermal conductivities of two cup-stacked carbon nanotubes and concurrently observed the internal hollow structures. We found that the sample with more structural disorders had a lower thermal conductivity. Our measurement method can pave the way to the sampleby-sample elucidation of the structure-property relationship for 1D materials.

Mastering thermal transport across carbon nanotube contacts through morphological control

“…Since the Pt nanofilm sensor is used as a resistive thermometer, prior to the thermal resistance measurements, we calibrated the electrical resistancetemperature dependence of the nanofilm sensor at 278.15 K, 298.15 K, and 318.15 K (see Supplementary Note S2) for further measuring its thermal conductivity 11,30 before each contact between the two MWCNTs. In the calibration measurement, the silicon wafer with the nanofilm sensor was fixed on a Peltier stage which was mounted on the SEM sample platform.…”

“…Consequently, interfacial thermal transport between 1D materials may be influenced by the contact angles and diameters of each 1D material. For real interfaces, structural nonuniformity is inevitable in both the longitudinal and circumferential directions of the 1D materials in contact 11 . This includes nano-or molecular-level surface defects, contaminations, and shape variations, all of which can significantly influence the van der Waals forces and phonon spectrum matching at the interface.…”

“…They had to estimate the thermal resistance by measuring that of another sample with a similar suspension heat conduction length. This method introduced non-negligible uncertainty because nanoscale samples from the same batch, and even different parts within an individual sample, often exhibit variations in their structural characteristics and thermal transport properties 11,20,21 . Besides, they were not able to flexibly and dynamically adjust the contact morphology between the fixed samples.…”