Raman Scattering and Electronic States of Nanoscale Group 4 Materials

小行星9623315 本工作的目的是获得在真空中制备和研究的有序和无序半导体纳米系统的声子态的基本信息。 IV族材料声子的基础研究将通过干涉增强拉曼散射（IERS）方法在非常小的1-2nm纳米晶体的外延膜和在选定的晶体氧化物上生长的外延膜上进行。 结果将提供新的信息声子状态的非常小的微晶，没有化学吸附的物种，和微晶半导体层。 对于外延层的独特的表面几何形状，如表面二聚体和悬挂键的作用，拉曼散射的兴趣。 IERS将提供有关半导体/氧化物界面中界面键合的更多信息。 将研究吸附物原子对纳米尺度系统声子态的影响。 拉曼散射将被扩展为研究表面和近表面原子动力学和结构的工具。 互补镜面，偶极电子能量损失谱（EELS）的研究在硅，锗和碳纳米系统将提供信息带间电子跃迁的尺寸或薄膜厚度的减小，光学间隙和亚间隙状态的变化，以及化学吸附物种的影响。 利用高分辨EELS研究了脉冲激光沉积非晶类金刚石碳材料中近表面原子振动态的变化。 这些类金刚石薄膜的原位测量将允许一种手段，以增加4倍键合的陶瓷和薄膜。 随着凝聚态系统的尺寸在一维或多维上减小到纳米级水平，表面和近表面原子在决定物理和化学性质方面发挥着越来越重要的作用。 因此，当尺寸减小到1-2nm时，电子和声子态、磁性和光学性质受到显著影响。 在这样的系统中，有限尺寸的量子效应和新的键合几何结构的存在导致物理性质的非常实质性的变化。 因此，这种小规模系统的基础科学知识和潜在技术应用都具有相当大的当前兴趣。 不同类别的纳米系统将进行研究，以获得信息的振动状态和电子带间跃迁的有限大小和近表面原子的影响。 这些研究将涉及使用和扩展新的和正在开发的实验方法，用于研究有序和无序的纳米级系统。 双层干涉增强拉曼散射（IERS）方法的改进将增强拉曼散射作为纳米晶岛颗粒和外延层形式的ZnO半导体及其界面的表面科学工具。 此外，反射电子能量损失谱（EELS）将被用于新的带间电子态的纳米晶，非晶和外延薄膜的研究。 这些有序和无序的纳米级半导体的研究将采用沉积的纳米薄膜，并在专门的超高压系统中原位研究。 ***

9623315 Lannin The objectives of this work are to obtain basic information on the phonon states of ordered and disordered semiconducting nanoscale systems prepared and studied in ultrahigh vacuum. Basic studies of the phonons of group IV materials will be performed by interference enhanced Raman scattering (IERS) methods on ultrathin films of very small, 1-2nm, nanocrystallites and on ultrathin films epitaxial layers grown on selected crystalline oxides. The results will provide new information about the phonon states of very small crystallites, without chemisorbed species, and ultrathin crystalline semiconductor layers. For epitaxial layers the distinct surface geometry, such as the role of surface dimers and dangling bonds on Raman scattering are of interest. IERS will provide additional Information about interfacial bonding in semiconductor/oxide interfaces. The influence of adsorbate atoms on the phonon states of nanoscale systems will be studied. Raman scattering will be expanded as a tool for the study of surface and near surface atom dynamics and structure. Complementary specular, dipolar electron energy loss spectroscopy (EELS) research in Si, Ge and C nanoscale systems will provide information about interband electronic transitions with decreasing size or film thickness, about changes in the optical gap and subgap states, and the effects of chemisorbed species. Changes in the vibrational states of near surface atoms in amorphous diamond-like carbon materials prepared by pulsed laser deposition will be studied by high resolution EELS. These in situ measurements of diamond-like films will allow a means to increase 4-fold bonding in ultrathin and thin films. %%% As the size of condensed matter systems is reduced in one or more dimensions to nanoscale levels, surface and near surface atoms play an increasingly important role in determining physical and chemical properties. Thus electrons and phonon states, magnetic and optical properties are su bstantially influenced when dimensions decrease to a scale of 1-2nm. In such systems finite size quantum effects and the presence of new bonding geometries lead to very substantial changes in physical properties. Both basic scientific knowledge and potential technological applications of such small scale systems are thus of considerable current interest. Different classes of nanoscale systems will be studied to obtain information on the effects of finite size and near surface atoms on both the vibrational states and electronic interband transitions. These studies will involve the use and extension of new and developing experimental methods for studies of both ordered and disordered nanoscale systems. Improvements in bilayer interference enhanced Raman scattering (IERS) methods for ultrathin films in the form of nanocrystalline island particles and epitaxial layers will enhance Raman scattering as a surface science tool for ultrathin semiconductors and their interfaces. In addition, reflection electron energy loss spectroscopy (EELS) will be utilized for new interband electronic state studies of nanocrystalline, amorphous and epitaxial ultrathin films. These studies of ordered and disordered nanoscale semiconductors will employ ultrathin films deposited and studied in situ in a specialized uhv system. ***