Description
Date/Time: 04-23-2019 - Tuesday - 05:00 PM - 07:00 PM
Pengyu Yuan1 2 3

1, University of California, Merced, Merced, California, United States
2, University of California, Berkeley, Berkeley, California, United States
3, Lawrence Berkeley National Laboratory, Berkeley, California, United States

Scanning electron microscopy (SEM) is ubiquitous for imaging but is not generally regarded as a tool for thermal measurements. The electron-beam stands out as a heat source with the almost highest energy density yet available (~100 kW/cm^2), the ease of controlling the intensity, shape, and position of the electron-beam, in addition to its high energy density, makes electron-beam heating highly advantageous. Especially, its capability of heating an extremely small area lends itself to explore thermal phenomena in micro/nanoscale for materials with different geometries, such as thin film, nano-fiber/tube, and nanoparticles. Recent experiments on nanoscale heat transfer show that the measured heat flow depends not only on nanostructure geometries and sizes but also on heater sizes and heating frequencies. (1) (2) (3) Compared with widely used laser heating source, heating from electron-beam is worth more attention to studying low-dimensional materials by its high coefficient of energy absorption by materials, high energy density, and a vacuum environment preventing oxidation or other contaminations. (4)
In the past few years, the heating mechanism of electron beam upon its hitting on a target has been theoretically predicted and estimated, but experimental characterization has been seldom presented. Here, we reported a systematically quantitative evaluation of electron-beam heating of silicon nitride membranes with a thickness ranging from ~100 nm to ~400 nm. The membrane is suspended by long thin beams and features an integrated serpentine Platinum resistor that can be employed to measure the temperature rise induced by electron-beam. Whenever the membrane thickness is smaller than the penetration depth of electron-beam, more electron will transmit through the membrane, and this makes the electron-beam heating less efficient. The most efficient heating electron beam voltage varies with the thickness and can be well determined by both experiment and Monte Carlo calculation, and this provides a new way to determine the thin film thickness. Results will also be presented for our preliminary efforts to use this controllable nanoscale heater to characterize the conductive and radiative thermal properties of other nanostructures.
This electron-beam heating characterization study will pave the way to fulfill the heat transfer model that cannot be described by classical rules, such as the Fourier’s law and Plank’s blackbody limit. Besides, this will also support the experiment methods development for SEM thermometry, and sufficient spatiotemporal resolutions to characterize anisotropic, size-dependent, and frequency-dependent thermal transport based on the electron-beam source.
1. J. K. Yang et al., Nature Nanotechnology 7, 91 (Feb, 2012).
2. D. Ding, X. Chen, A. J. Minnich, Applied Physics Letters 104, (Apr 7, 2014).
3. K. T. Regner et al., Nat Commun 4, 1640 (Mar, 2013).
4. W. T. Yan, J. Smith, W. J. Ge, F. Lin, W. K. Liu, Comput Mech 56, 265 (Aug, 2015).

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