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Details of Grant 

EPSRC Reference: EP/K001515/1
Title: Precursor Chemistry and the CVD of Transparent Conducting Oxides
Principal Investigator: Carmalt, Professor C
Other Investigators:
Parkin, Professor IP
Researcher Co-Investigators:
Project Partners:
NSG Group (UK)
Department: Chemistry
Organisation: UCL
Scheme: Standard Research
Starts: 01 December 2012 Ends: 31 October 2016 Value (£): 461,645
EPSRC Research Topic Classifications:
Materials Characterisation Materials Synthesis & Growth
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:
Panel DatePanel NameOutcome
26 Jul 2012 EPSRC Physical Sciences Materials - July Announced
Summary on Grant Application Form
This project will involve the investigation of alternative precursors and deposition technologies in order to improve performance and enable next generation transparent conducting oxide (TCO) films to be developed.

Indium tin oxide (ITO) is the current TCO of choice for most industrial applications but it has many limitations, such as modest conductivity (2000-4000 S/cm), a relatively low work function and some optical absorption in the blue-green spectral region. In addition, indium is expensive since it is in relatively short supply, which presents a significant challenge for larger-scale production of next generation photovolatic technologies and flat panel displays. It is therefore crucial to develop alternative TCO materials with no indium with improved optical and electrical properties. Alternatives to ITO include doped ZnO (ZnO:Al, ZnO:Ga, ZnO:SnO2) and doped SnO2 (SnO2:Sb, SnO2:F, ZnO-SnO2) and many of these have been investigated in their bulk form. However, studies of some of these materials as thin films is limited and for many of the applications thin films are required. An ideal method for preparing thin fims for large scale applications is chemical vapour deposition (CVD) given that films with good uniformity and compositional control, large area growth and step coverage can be achieved. However, for a successful CVD process, a volatile precursor is necessary which is prefereably a liquid or low metling solid for atmospheric pressure CVD or highly soluble for liquid based (aerosol assisted) CVD. Current precursors to TCO materials, particularly indium and zinc still suffer from chemical instability, poor reproducibility in the growth process and less than favourable vapour pressures and reactivity for film growth.

This work aims to develop highly volatile and soluble precursors based on metal ketoiminates. The advantages of using the ketoiminate ligand include:

- reactive complexes can be formed in high yield

- complexes with a hign vapour pressure can be formed as monomeric species are isolated

- thermal stability of the metal complexes can be increased by tuning the groups attached to the nitrogen atoms

- the surface reaction between the metal precursor and the surface of the substrate can be enhanced due to the high chemical reactivity of the complexes.

TCO materials to be investigated include doped-ZnO and doped-SnO2. We have the ability to lay down thin films using a new combinatorial aerosol-assisted (AA)CVD reactor for solution based and also a combinatorial APCVD reactor to make films of graded composition. This new reactor enables upto 400 different compositions to be made on a single plate in one CVD experiment. This is important as it will enable us to rapidly screen composition space make idealised and optimised compositions for TCO applications. This combined approach will enable us to investigate different combinations and go towards achieving the next generation TCO materials.
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