Probing Lattice Vibrations at SiO$_{2}$/Si Surface and Interface with Nanometer Resolution
Yue-Hui Li1,2†, Mei Wu1,2†, Rui-Shi Qi1, Ning Li1,2, Yuan-Wei Sun1,2, Cheng-Long Shi3, Xue-Tao Zhu4, Jian-Dong Guo4, Da-Peng Yu2,5,6, Peng Gao1,2,6**
1International Center for Quantum Materials, Peking University, Beijing 100871 2Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871 3Nion Company, 11511 NE 118Th Street, Kirkland, Washington State 98034, USA 4Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 5Shenzhen Key Laboratory of Quantum Science and Engineering, Shenzhen 518055 6Collaborative Innovation Centre of Quantum Matter, Beijing 100871
Abstract：Recent advances in monochromatic aberration corrected electron microscopy make it possible to detect the lattice vibrations with both high-energy resolution and high spatial resolution. Here, we use sub-10 meV electron energy loss spectroscopy to investigate the local vibrational properties of the SiO$_{2}$/Si surface and interface. The energy of the surface mode is thickness dependent, showing a blue shift as $z$-thickness (parallel to the fast electron beam) of SiO$_{2}$ film increases, while the energy of the bulk mode and the interface mode keeps constant. The intensity of the surface mode is well-described by a Bessel function of the second kind. The mechanism of the observed spatially dependent vibrational behavior is discussed and compared with dielectric response theory analysis. Our nanometer scale measurements provide useful information on the bonding conditions at the surface and interface.
2019, Vol. 36 
