Temperature-Dependent Thermal Diffuse Scattering Measurements of Nanomaterials using Scanning Transmission Electron Microscopy

G. Wehmeyer
Rice University,
United States

Keywords: nanomaterials, electron microscope, thermal management, temperature mapping

Summary:

Novel methods to measure temperature (T) of nanomaterials with improved spatial resolution would be useful for thermal researchers interested in quantifying hotspots in microelectronic applications or designing thermal managements systems for nanotechnologies. Recent scanning Transmission Electron Microscopy (TEM) thermometry techniques open new possibilities for mapping T of thin samples with 1000 ppm/K at room temperature. This T-dependent TDS has not been leveraged for STEM thermometry, however, because the Debye-Waller effect on the Bragg peak intensity is typically overwhelmed by the effects of thermal tilts and thermal drift. Here, we discuss our early progress in demonstrating temperature-dependent TDS measurements using TEM by measuring the diffuse background intensity (rather than the Bragg peak intensity) in energy-filtered scanning electron nanodiffraction patterns. Applying virtual apertures to these diffraction patterns during post-processing allows us to quantify the T-dependent TDS in the diffuse background between the Bragg spots; we find that this diffuse signal is relatively insensitive to thermal tilts and drift and more convenient for practical thermometry. Using this diffuse TDS signal, we measure a position-averaged temperature coefficient of 2400±400 ppm/K for a single-crystal gold film averaged between T=100 K and T=300 K, and compare our results with the predictions of Debye-Waller theory. The measurements display typical temperature uncertainties of 8 K and temperature sensitivities of 51 K Hz^-1/2. We will also discuss our recent attempts to measure T-dependent TDS using the more convenient annular dark field detection technique. Our TDS-based TEM thermometry demonstration provides a step towards the goal of non-contact nanoscale temperature mapping of thin nanostructures or microelectronics. More generally, the work described here illustrates how recent advances in transmission electron microscopy hardware and software can enable new nanomaterial characterization capabilities that may lead to improved performance of nanotechnologies.