Low Temperature Nuclear Spin Relaxation and the Structure and Dynamics of Defects in Materials

该项目将为量子固体和量子薄膜以及材料缺陷的联合理论和低温实验研究提供支持。对氢、氘分子和稀有气体原子在氧化镁、氮化硼、硅上物理吸附成薄膜进行理论和脉冲核磁共振研究。这些分子和原子也将在非磁性宿主和在低温核磁共振（NMR）金刚石砧细胞的高压下作为基质分离的物种进行研究。多自旋回声独特的吸附物种将用于检查动力学和相变在高密度和有限的维度。一项密切相关的工作将在光诱导材料电子特性发生亚稳态变化的条件下检查非晶半导体薄膜中的氢和氘。理论上的努力将包括对含有各种掺杂剂的非晶硅大型超级电池的第一性原理分子动力学模拟。该项目将为量子固体和量子薄膜以及材料缺陷的联合理论和低温实验研究提供支持。对氢、氘分子和稀有气体原子在氧化镁、氮化硼、硅上物理吸附成薄膜进行理论和脉冲核磁共振研究。这些材料也将在高压下进行检验。该研究涉及与材料缺陷以及这些缺陷在决定材料性能中的作用相关的基础主题以及技术上重要的主题。例如，掺杂各种原子的非晶半导体将被研究，以更多地了解这些用于光导太阳能电池的材料的特性。该研究有助于揭示目前制约光电池效率和实际应用的亚稳态特性。* * *

9305344 Norberg This project will provide support for a joint theoretical and low temperature experimental study of quantum solids and films and of defects in materials. Theoretical and pulsed nuclear magnetic resonance investigations will be carried out on molecular hydrogen and deuterium and rare gas atoms physisorbed as thin films on magnesium oxide, boron nitride, and silicon. These molecules and atoms will also be studied as matrix-isolated species in non- magnetic hosts and at high pressures in a cryogenic nuclear magnetic resonance (NMR) diamond anvil cell. Multiple spin echoes unique to adsorbed species will be used to examine dynamics and phase transitions at high densities and under restricted dimensionality. A closely related effort will examine hydrogen and deuterium in amorphous semiconducting films under conditions where light-induced metastable changes in the electronic properties of the materials occur. The theoretical effort will include first principles molecular dynamics simulations on large supercells of amorphous silicon containing various dopants. %%% This project will provide support for a joint theoretical and low temperature experimental study of quantum solids and films and of defects in materials. Theoretical and pulsed nuclear magnetic resonance investigations will be carried out on molecular hydrogen and deuterium and rare gas atoms physisorbed as thin films on magnesium oxide, boron nitride, and silicon. These materials will also be examined at high pressures. The research involves fundamental topics as well as technologically important subjects related to defects in materials and the role these defects play in determining materials properties. For example, amorphous semiconductors doped with various atoms will be investigated to learn more about the properties of these materials which are used in photoconducting solar cells. The research should shed light on the metastable properties of the photocells which at present li mit their efficiency and practical utility. ***