论文标题
同时激发具有高能量电子束的中心和布里鲁因区域的边界
Simultaneous excitation of phonons at the center and boundaries of Brillouin zones with high energy electron beams
论文作者
论文摘要
现在，高能电子束现在可以通常将注意力集中在1-2Å上，并具有在扫描透射电子显微镜（STEM）中使用单色电子损坏光谱（EEL）从材料中获取振动信息的能力。这里表明，可以用轴上振动的茎鳗同时探测长波长和短波长的声子。使用聚焦电子束的优点是，短波长的声子是通过冲击散射探测的，而长波长模式是通过偶极散射探测的。通过扫描电子束穿过六角硼硝酸纳米颗粒的边缘，可以证明短波长度的局部特征。发现高空间分辨率茎成像所需的条件也与增强短波长声子对振动能量损失光谱的贡献的条件相关。用高空间分辨率探测短波长的声子，并具有轴上振动的鳗鱼，将有助于在材料中原子量尺度异质性的振动激发与粘结布置之间建立基本联系。
High energy electron beams can now be routinely focused to 1-2 Å and offer the ability to obtain vibrational information from materials using monochromated electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Here it is shown that long and short wavelength phonons can be probed simultaneously with on-axis vibrational STEM EELS. The advantage of using focused electron beams is that the short wavelength phonons are probed via impact scattering while the long-wavelength modes are probed via dipole scattering. The localized character of the short-wavelength modes is demonstrated by scanning the electron beam across the edge of a hexagonal boron nitride nanoparticle. It is found that the condition required for high spatial resolution STEM imaging also correlates with the condition to enhance the short-wavelength phonon contribution to the vibrational energy-loss spectrum. Probing short-wavelength phonons at high spatial resolution with on-axis vibrational STEM EELS will help develop a fundamental connection between vibrational excitations and bonding arrangements at atomic scale heterogeneities in materials.
