Nanostructuring of Advanced Materials
Synthesis of Precursors for Single Source Chemical Vapour Deposition (SSCVD)
Single source chemical vapour deposition utilizes specialized precursors which contain a core of the components of the desired film. This core is surrounded by organic ligands which impart volatility to the compound. When the precursor is sublimed under vacuum conditions onto a heated substrate the ligands surrounding the core decompose and a film is grown. This technique utiliizes a simple experimental setup but requires specialized precursors.
This part of the project involves developing new precusors for SSCVD film growth. FIlms including ZnO, ZnS and MgO have been grwon using this technique. New precursors are being developed to improve the properties of the films obtained as well as to begin depositing other types of films.
Nucleation Mechanisms of Semiconductor Films
Semiconductor films grown using the SSCVD method described above have been examine dusing various microscopy techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has been found that the film nucleation mechanisms described for sputtered films do not fully describe the microstructure of films grown using SSCVD. The effect of substrate geometry on film growth has also been investigated including oblique deposition and the effect of substrate curvature.
Deep Level Defects in ZnO
The Phenomena of lasing from random materials is not well understood. It is thought that defects within the material may act as an optical cavity amplifying light in place of the mirros used in conventional lasers. In this study we look at the defects produced in ZnO films using the SSCVD method of film growth. The origins of the defects have been investigated using cathodoluminescence and synchrotron techniques such as EXAFS. Assigning defect emissions is not straightforward and this project is ongoing.
If the defect mechanisms can be understood the it may be possible to enhance light emission from these random media and hence create reliable lasers from disordered materials.