Microscopic motion of hydrogen in the dilute and clustered phases of hydrogenated amorphous silicon

Abstract

1H NMR dipolar echo measurements have been performed on a series of B-doped, P-doped, compensated and intrinsic a-Si:H samples. At room temperature the dipolar spin lattice relaxation time, T 1D, correlates with the macroscopic diffusion constants as determined by SIMS experiments. The local jump frequencies determined from these values of T 1D are orders of magnitude faster than those inferred from the macroscopic diffusion results and the associated activation energies are much less (∼ 0.2 eV). At 150 K and 100 K the dipolar echo in 10 −3 P-doped a-Si:H exhibits both a narrow line and a broad line. The full widths at half maximum of the narrow line and the broad line are the same as those of the narrow and broad components of the free induction decay, respectively. Because the narrow line exhibits a T 1D with a slightly different temperature dependence from the T 1D for the broad line the local motion is slightly different for hydrogen atoms in the clustered and dilute phases.