Fig. 3: Asymmetric spectral intensities of Si OM near the gradual and abrupt interfaces.
From: Nanoscale imaging of phonon dynamics by electron microscopy
a, Two-dimensional spatial map of Si OM intensity of a 35 at.% average Ge composition QD. The red and blue contrast extremes denote high and low relative mode intensities. b, Absolute value of the vertical gradient of the elemental map in Fig. 2a, emphasizing relative interface abruptness. Scale bars in a–c are 10 nm. c, Boltzmann transport simulated mapping of non-equilibrium phonon enhancement of Si OM with top interface SR = 0 and bottom interface SR = 1. Simulation was carried out only for the Si side and only normal incident phonons are considered. Phonons with oblique incidence do not contribute to the enhancement of EELS intensity. The red colour in the map denotes a greater enhancement of non-equilibrium phonons. d, Ten horizontal, pixel-averaged 1D profiles of the maps in a and b (white shaded regions). The 1D intensity line profile of a is plotted with the histogram profile of b. Error bars represent standard deviation. e, Plot of Si OM intensity enhancement as a function of maximal Ge composition in the QD.
