Floating bond defects

An argument against the defect mediated diffusion model is the same one used earlier that is, there are not enough defects as determined by ESR (Brodsky and Title, 1969, 1976) or Deep Level Transient Spectroscopy measurements (Johnson, 1983) to account for the motion of all of the bonded hydrogen in a-Si H. This objection is removed if the floating bonds are 104-106 times more mobile than the hydrogen atoms. However, such highly mobile defects would rapidly self-annihilate via the process. 

The ESR data clearly indicate that the 2.0055 defect has an odd value of Az and so the discussion reduces to the choice of dangling bonds or floating bonds. The following arguments have been given for and against the two possibilities ... 

To investigate the crystallization phenomena induced by the external field, a cyclic force is imposed on a small portion of molecules in the amorphous structure, in addition to tiie inherent intermolecular forces. As a practical matter, this force may be applied to susceptor molecules (molecules witii dangling or floating bonds, or other defects) tiirough direct electric fields, electric fields induced by the external magnetic field, or other excitation sources. In tiiis study, it is assumed that some molecules can act as susceptors of the external field, for tiie sole purpose of inducing artificial molecular movements selectively and of observing tiie subsequent crystallization behavior. As discussed previously, the results of this study could provide a clue to mechanisms involved in the athermal crystallization of a-Si to poly-Si, which is induced by the field-enhanced molecular movements. 

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