The structures and energies of eight fully saturated polycyclic polysilanes (Si6H8, Si6H10, Si7H8, Si7H10, Si8H12, Si9H14, Si10H14, and Si10H16) were investigated using ab initio molecular orbital calculations. Structures and vibrational frequencies were computed at the HF/3-21G(d) level. A complete basis set extrapolation method (CBS-4) was used to calculate the energies of the structures. Heats of formation were evaluated based on homodesmotic reactions involving disilane, trisilane, and isotetrasilane. The calculations predict a negative free energy of reaction for cluster formation from silane (with H2 as a by-product) for conditions typically used in chemical vapor deposition of silicon from silane.
Bibliographical noteFunding Information:
This work was partially supported by Advanced Silicon Materials, Moses Lake, WA, by the Semiconductor Research Corporation, and by the Minnesota Supercomputer Institute. We are grateful to Gernot Katzer and his colleagues at the University of Graz for helpful discussions and access to unpublished details of their calculations.