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

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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. ***