Photo-Induced Structural Changes on Semiconductor Surfaces

半导体表面光致结构变化

• 批准号: 08640416
• 负责人: KANASAKI Jun'ichi
• 金额: $ 0.64万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640416/
• 关键词: semiconductor; surface; laser; photo-induced structural change; photo-induced desorption; silicon; Indium Phosphide; scanning tunneling microscopy; 半導体表面; 電子励起誘起脱離

Structural changes and desorption of constituent atoms induced by irradiations of Si (111) - (7x7) and InP (l10) surfaces have been studied by means of scanning tunneling microscopy (STM) and high-sensitivity measurements of desorbed species using resonant- and non-resonant ionization spectroscopy. For Si (111) - (7x7) surfaces, it has been shown that excitation with laser pulses with low intensity induces vacancies selectively at surface adatom-sites, via electronic bond-breaking, accompanied with desorption of Si atoms of electronic ground state. Statistical investigation of spatial distribution of the laser-induced vacancies have revealed strong site-dependence of the bond-breaking efficiency. The efficiency stays constant with increasing the dose of excitation laser pulses, meaning that the site-dependence is not due to any accumulative effects but a characteristic feature of bond-breaking induced within a single laser pulse. The present study also shows that the electronic bond-br … More eaking exhibits strong photon-energy and fluence dependent efficiency, and that the translational energy distribution of desorbed Si atoms independent of wavelength, fluence and time duration of excitation laser lights. Experimental results obtained in the present study have shown that non-linear localization of surface electronic excitations selectively at surface adatom sites plays an important role on the photo-induced bond-breaking on the Si (111) - (7x7) surface. Based on the detail analyses of the results, we have proposed a desorption mechanism including two-hole localization on a surface atomic site followed by bond-breaking via phonon-kick process.Similarly, excitation between surface electronic bands on InP (110) - (lxl) induces an electronic bond-breaking with a strong site-dependent efficiency : laser irradiation produces vacancies selectively at P sub-lattice. In addition, it has been also shown that vacancy-strings elongated selectively along In-P chains are formed efficiently with increasing excitation dose, meaning preferential bond-breaking at atomic sites neighboring to vacancies. The total number density of vacancy string with respective sizes increases linearly for low dose range, and then saturates at a few percent of monolayer. Since the laser-induced change of the number of perfect lattice sites is little, the saturation of number density of vacancies suggests strongly the decrease of bond-breaking efficiency. The efficiency of electronic bond-breaking at perfect lattice sites shows non-linear increase with increasing dose, suggesting that non-linear process are included in the bond-breaking. Based on analyses of the non-linear efficiency, we suggest that two-hole localization is included as a primary step of the electronic bond-breaking. Experimentally observed saturation of the efficiency may be explained by efficient transfer and trapping of photo-generated surface free holes, which are extended quasi-one dimensionally along the In-P chain.The present study have demonstrated that the surface electronic excited states on semiconductor surfaces are localized non-linearly with a strong site-selective efficiency, leading to breaking of local atomic bonds. Observed difference in geometric feature and efficiency of structural changes on the two surfaces may indicate that the electronic bond breaking depends strongly on structural and electronic properties of the surfaces. Less

利用扫描隧道显微镜（STM）和共振和非共振电离光谱对解吸物质的高灵敏度测量，研究了Si (111) - (7x7)和InP（1010）表面辐照引起的组成原子的结构变化和解吸。对于Si (111) - (7x7)表面，低强度激光脉冲激发通过电子断键在表面原子位置选择性地诱导出空位，并伴有Si原子的电子基态解吸。对激光诱导空位空间分布的统计研究表明，断键效率具有很强的位置依赖性。随着激发激光脉冲剂量的增加，效率保持不变，这意味着位置依赖性不是由于任何累积效应，而是单个激光脉冲内诱导断键的特征。本研究还表明，电子键br…More eaking表现出很强的依赖于光子能量和通量的效率，并且解吸Si原子的平动能量分布与激发激光的波长、通量和持续时间无关。本研究的实验结果表明，在Si (111) - (7x7)表面上，表面电子激发选择性的非线性局域化在光诱导断键过程中起着重要作用。在详细分析结果的基础上，我们提出了一种脱附机制，包括在表面原子位置上的双空穴定位，然后通过声子踢断过程破坏键。同样，InP (110) - (lxl)表面电子带之间的激发诱导了电子断键，具有很强的位依赖效率：激光照射在P亚晶格上选择性地产生空位。此外，研究还表明，随着激发剂量的增加，沿In- p链选择性拉长的空位链可以有效地形成，这意味着空位附近的原子位点会优先断裂键。不同尺寸空位弦的总数目密度在低剂量范围内呈线性增加，然后在单层的几个百分点处达到饱和。由于激光诱导的完美点阵数目变化不大，空位数目密度的饱和强烈表明断键效率的降低。完美点位的电子断键效率随剂量的增加呈非线性增长，表明断键过程包含非线性过程。基于非线性效率分析，我们认为双空穴局部化是电子断键的首要步骤。实验观察到的效率饱和可以用光产生的表面自由空穴的有效转移和捕获来解释，这些空穴沿In-P链呈准一维扩展。本研究表明，半导体表面的表面电子激发态是非线性局域化的，具有很强的位置选择效率，导致局部原子键的断裂。观察到的两种表面结构变化的几何特征和效率的差异可能表明，电子键断裂在很大程度上取决于表面的结构和电子性质。少

项目成果

K.Tanimura: "Laser-Induced Bond Breaking and Structural Changes on Si(111)7x7 Surfaces" Applied Surface Science. 127. 33-39 (1998)

K.Tanimura：“Si(111)7x7 表面上的激光诱导键断裂和结构变化”应用表面科学。

K.Tanimura: "Laser-Induced Bond Breaking and Structural Changes on Si(111)7x7 Surfaces" Applied Surface Science. 127-129. 33-39 (1998)

K.Tanimura：“Si(111)7x7 表面上的激光诱导键断裂和结构变化”应用表面科学。

N.Itoh: "Laser-Induced Desorption from STM-Selected Semiconductor Sites" Progress in Surface Science. in press.

N.Itoh：“STM 选择的半导体位点的激光诱导解吸”表面科学进展。

K.Tanimura and J.Kanasaki: "Laser-Induced Bond Breaking and Structural Changes on Si(111)7*7 Surfaces" Applied Surface Science. 127. 33-39 (1998)

K.Tanimura 和 J.Kanasaki：“Si(111)7*7 表面上的激光诱导键断裂和结构变化”应用表面科学。

N.Itoh, J.Kanasaki, and J.Xu: "Laser-Induced Desorption from STM-Selected Semiconductor Sites" Progress in Surface Science. (in press.).

N.Itoh、J.Kanasaki 和 J.Xu：“STM 选择的半导体位点的激光诱导解吸”表面科学进展。