PSI - Group

Hydrogen Chemistry and Dynamics using ERDA microscopy

taff : IZ Machi (UNISA), SH Connell (WITS), E Siders-Haddad (Wits), D Rebuli (Wits)
Students : AU Naran (Uni. Eduardo Mondlane), J Sithole (UNISA), D Dube (Wits)
Collaborators : 
JE Butler (NRL-Washington), P Aggerholm (Aarhus) K Bharuth-Ram (Natal)

The capability to perform 3-dimensional microscopy of trace hydrogen distributions
has been developed at the EN-Tandem accelerator at the Schonland Research Centre of

Hydrogen can passivate electrically active dopants in electronic diamond
It catalyses the synthesis of CVD diamond, and may have a srelated role in HTHP diamond
It occurs in molecular systems inside diamond which theoretically are expected to act as shallow dopants
It has an interesting diffusion behaviour, where coherent mechanisms may play an important role.

The Muonium based studies are related to thee  .... as muonium is a hydrogen chemical analogue.

The major result so far is the unexpected deep trapping of high dose implanted
hydrogen and the 3D imaging of natural and implanted hydrogen distributions.
The deep trapping may be the result of the stability auto-trapping configurations.
An open question which remains is why Bond Centred hydrogen has not yet been seen,
while Bond Centered muonium is readily observed. The reason is suspected to be
due to even more stable trapping of hydrogen at defects involving C-H bonds.

Other studies investigated the expected higher mobility of the H+ ion, as
well as passivation by hydrogen of acceptors and donors.

Hydrogen distributions due to synthesis conditions may be identified.