Deuteron Magnetic Resonance in Amorphous Silicon and Germanium.

Plasma-deposited thin films of a -Si(H,D) and a-Ge(H,D) have been characterized by deuteron magnetic resonance. Measurements of spin-lattice relaxation times and line shapes were made between 2 and 320 K to determine the structural role played by hydrogen and deuterium in these samples. Deuterium in Si-D and Ge-D bonded configurations exhibited Pake doublets with temperature independent splittings of 66 kHz and 60 kHz respectively. A broad central component with a temperature independent 34 kHz line width was identified as arising from matrix isolated D_2 and HD molecules. Multiple spin echoes from the HD molecules in these configurations were observed and their widths, amplitudes and time of occurrence were found to be related to their intramolecular dipole and quadrupole coupling strengths. Existence of the multiple echoes down to 4 K indicated significant admixtures of higher rotational J states into the J = 0 ground state caused by large crystalline field gradients arising from the silicon environment. A narrow central component whose line width varied from 300 Hz at 300 K to 5 kHz at 2 K was also observed. This component arose from D_2 and HD molecules contained in sample voids and the change in line width was due to the motional averaging of electric field gradients seen by the molecules. Spin-lattice relaxation was dominated by restricted spin diffusion of net magnetization to p -D_2 and HD relaxation centers. Below 40 K a 76 kHz doublet appeared from frozen out p -D_2 molecules whose transition rates amongst m_{rm J} sublevels was less than their intramolecular coupling frequency.