Dynamic properties of THz-phonons in semiconductor nano-structures

半导体纳米结构中太赫兹声子的动态特性

• 批准号: 09640385
• 负责人: TAMURA Shin-ichiro
• 金额: $ 1.98万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640385/
• 关键词: superlattice; nanometer; THz; surface phonon; transmission・renection times; phonon pulse; 透過・返射時間; 音響フォノン

The recent development in fabricating small structures makes it possible to control phononic properties by utilizing these structures of a nanometer scale. Thus the dynamic properties of phonons in nano-structures in a THz-frequency range is very important topic to be studied urgently, Experimentally, the picosecond light pulse method to generate and detect acoustic phonons in the 0.1 to 1 THz range (called as picosecond ultrasonics) has been developed. This method is specially powerful in studying the acoustic properties of thin films and multilayered elastic structures for a wide range of temperatures . However, theoretical studies on the new, interesting topics found by the picosecond ultrasonics are very few. The purpose of the present project is to elucidate theoretically, [I] anomalous reduction of vertical thermal conductivity in GaAS/AlAS superlattices measured by the picosecond ultrasonics and [II] the resonant interaction of the extended and surface localized phonons in multi … More layered periodic structures, which has been expected to be observed in the picosecond ultrasonics. The published work supported by this grant has been listed in a separate sheet. Here we briefly summarize the important results we obtained: (1) Different from the scattering in bulk materials the isotope scattering of phonons is anisotropic and mode dependent. We found that the longitudinal (L) phonons are scattered much weaker than the transverse phonons in superlattices for wide ranges of frequencies. Thus, the L phonons play important role in the heat transport in superlattices. (2) The reduction of thermal conductivity in superlattice is predicted due to the zone-folding and associated flattening of phonon dispersion curves near the mini-Brillouin zone center and boundary. However, the effects are smaller than those measured for GaAS/AlAS samples. This suggests that anharmonic mini-Umklapp scattering on phonons should be the main source for the measured large reduction of the vertical thermal conductivity in superlattices. (3) The transmission and reflection of a rectangular phonon packet for the GaAs-(GaAs/AlAsィイD2NィエD2-HィイD22ィエD2O and Al-(Al/polymer)ィイD2NィエD2-HィイD22ィエD2O systems are studied. A prominent feature predicted is the double-peak structure of the reflected packet. The physical origin is the resonance of the incident packet with the localized vibrational mode at the surface of the superlattice. Less

最近在制造小结构方面的发展使得通过利用这些纳米尺度的结构来控制声子性质成为可能。因此，太赫兹频率范围内纳米结构中声子的动力学性质是一个非常重要的研究课题。在实验上，已经发展了产生和探测0.1 ~ 1 THz范围内声学声子的皮秒光脉冲方法（称为皮秒超声）。这种方法在研究薄膜和多层弹性结构在宽温度范围内的声学特性时特别强大。然而，对皮秒超声所发现的新的、有趣的课题的理论研究却很少。本项目的目的是从理论上阐明[I]通过皮秒超声测量的GaAS/AlAS超晶格中垂直热导率的异常降低和[II]多晶格中扩展和表面局域声子的共振相互作用 ...更多信息 层状周期性结构，这是预期在皮秒超声波中观察到的。由该基金资助的已发表的作品已在另一张纸上列出。本文简要总结了我们所得到的重要结果：（1）与体材料中的散射不同，声子的同位素散射是各向异性的，并且与模式有关。我们发现，在超晶格中，在很宽的频率范围内，纵向（L）声子的散射比横向声子弱得多。因此，L声子在超晶格的热输运中起着重要的作用。(2)超晶格中热导率的降低是由于微布里渊区中心和边界附近的区折叠和声子色散曲线的平坦化。然而，效果是小于那些测量的GaAs/AlAS样品。这表明，声子上的非谐微型Umklapp散射应该是超晶格中垂直热导率大幅降低的主要原因。(3)本文研究了GaAs-（GaAs/AlAs）-D_2N体系的矩形声子包的透射和反射。预测的一个突出特征是反射包的双峰结构。其物理起源是入射波包与超晶格表面局域振动模的共振。少

项目成果

Y.Tanaka: "Two-Dimensional Phononic Crystals : Surface Acoustic Waves"Physica B. 263-264. 77-80 (1999)

Y.Tanaka：“二维声子晶体：表面声波”Physica B.263-264。

Y.Tanaka: "Acoustic Stop Bands of Surface and Bulk Modes in Two-Dimensional Phononic Lattices Consisting of Aluminum and a Polymer"Phys.Rev.B. 60,19. 13294-13297 (1999)

Y.Tanaka：“由铝和聚合物组成的二维声子晶格中的表面和体模声阻带”Phys.Rev.B。

W.S.Capinski: "Analysis of the Isotope Scattering on the Thermal Conductivity of Crystalline Silicon"Phys.Rev.B. 59・15. 10105-10110 (1999)

W.S.Capinski：“晶体硅热导率的同位素散射分析”Phys.Rev.B. 10105-10110 (1999)

W.S. Capinski: "Analysis of the Isotope Scatteing on the Thermal Conductivity of Crystalline Silicon"Phy. Rev. B. 59,15. 10105-10110 (1999)

W.S.

Y.Tanaka: "Phonon focusing in superlattices" J.Phys.Condens.Matter. 10. 8787-8798 (1998)

Y.Tanaka：“超晶格中的声子聚焦”J.Phys.Condens.Matter。