Molecular complexation and defect dynamics in diamond by particle-sold interactions.

Doyle, Bryan Patrick
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This thesis addresses, as its primary topic, the behaviour of the heavy ion 111In in the diamond lattice. More specifically the lattice sites occupied after implantation and annealing have been investigated using the technique of 2-dimensional Conversion Electron Emission Channeling (CEEC). The study of a suite of carefully chosen, defectrich diamonds has allowed the investigation of In-defect interactions and any resultant complex formation. The experimental work has been supported by density functional theory calculations of the energetically most stable site for m Tn in pure diamond. We propose, following from the results in this thesis, that vacancies are the most important defect constituents in the final configurations of implanted and annealed indium in diamond. This is found to be the case independent of the other defects in the crystal, be they boron, hydrogen or nitrogen in different forms. The possibility of hydrogen complexation is however not excluded. The origin of the random fraction measured in previous studies is proposed to be partially due to In in different multi-vacancy complexes. Theoretically the most stable site for the In was found to be bond-centred in a di-vacancy. Secondarily, the behaviour of hydrogen in diamond has been investigated through Elastic Recoil Detection analysis (ERDA). Diamond has a natural abundance v; hydrogen. In order to fully interpret any In-H interactions th at occur it is necessary to better understand the mobility of hydrogen in the diamond lattice. To this end Che d'hu.-ion of both implanted and plasma loaded hydrogen has been studied. The naturally occurring hydrogen distributions in natural as well as in synthetic diamonds have also been studied with the same aim in mind. The ERDA measurements have necessitated the development of a sophisticated 3-dimensional ERDA system utilising a 2-dimensional position sensitive detector. The evolution of ERDA at this laboratory into a routine analytical tool has been a necessary part of this work. The mobility of hydrogen or lack thereof has been found to be dependent on various factors. These include the starting configuration of the hydrogen species and whether pre-damage through ion implantation has been made to the crystal. The work of this thesis is important in two contexts. Indium is a heavy ion and the results stress the importance of vacancies, both singly and multiply, in heavy ion implantation. This has ramifications for those wishing to use heavy ions in the fabrication of diamond electronic devices. Hydrogen is a common impurity in diamond and the findings here on its mobility (and lack thereof) are of relevance to the diamond physics community.