Microstructure from joint analysis of experimental data and ab initio interactions: Hydrogenated amorphous silicon
Abstract
A study of the formation of voids and molecular hydrogen in hydrogenated amorphous silicon is presented based upon a hybrid approach that involves inversion of experimental nuclear magnetic resonance data in conjunction with ab initio total-energy relaxations in an augmented solution space. The novelty of this approach is that the voids and molecular hydrogen appear naturally in the model networks unlike conventional approaches, where voids are created artificially by removing silicon atoms from the networks. Two representative models with 16 and 18 at. % of hydrogen are studied in this work. The result shows that the microstructure of the a-Si:H network consists of several microvoids and few molecular hydrogen for concentration above 15 at. % H. The microvoids are highly irregular in shape and size, and have a linear dimension of 5–7 Å. The internal surface of a microvoid is found to be decorated with 4–9 hydrogen atoms in the form of monohydride Si–H configurations as observed in nuclear magnetic resonance experiments. The microstructure consists of (0.9–1.4)% hydrogen molecules of total hydrogen in the networks. These observations are consistent with the outcome of infrared spectroscopy, nuclear magnetic resonance, and calorimetry experiments.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 28, 2014
- Source ID
- 10.1063/1.4905024
Entities
People
- David Drabold
- Parthapratim Biswas
- Raymond Atta-fynn
Organizations
- Army Research Office
- Ohio University
- University of Southern Mississippi
- University of Texas at Austin