Effect of Light Soaking on the Local Motion of Hydrogen in Hydrogenated Amorphous Silicon

ABSTRACTPrevious measurements of local hydrogen motion in intrinsic, doped, and compensated hydrogenated Amorphous silicon (a-Si:H) using the 1H nuclear magnetic resonance (NMR) dipolar echo method have shown that the local hydrogen motion is much faster than the macroscopic diffusion would indicate but that the local motion follows the same trends with doping and defect density as the macroscopic diffusion. We report the effect of light soaking on the local motion of hydrogen in hydrogenated Amorphous silicon. Measurements are presented on 10−3 P-doped a-Si:H at 297 K. After light soaking with infrared-filtered, white light of intensity -400 MW/cm2 for 75 hours, the electron spin resonance (ESR) spin density increases to -101 spins/cm After light soaking 1H NMR dipolar echo measurements on this sample show that the dipolar spin-lattice relaxation time, T1D, is ∼4 Ms. After thermal annealing at 190 C for two hours the value of T1Dreturns to its pre-irradiation value of ∼ 11 Ms. The local rate of motion, which scales with TID-1 thus increases with the paramagnetic defect density. The general implications of this result for descriptions of both microscopic and macroscopic Motion of hydrogen in a-Si:H are discussed.