Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.778963
Title: The effects of hydrogen, oxygen and water vapour on the work function and resistance of titanium films
Author: Kandasamy, K.
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 1980
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Abstract:
The changes of work function; ? and resistance; R of titanium films were measured in U.H.V. at room temperature, when- hydrogen, oxygen and water vapour interacted with them. The interaction of hydrogen reduced R by 30% after an initial increase of 1% of its initial resistance RQ. The initial increase of ? by 50meV was followed by a decrease of 300meV and then by an increase of 125-150meV. It was found that the high composition hydride (> TiH1.9) was unstable in high vacuum and the dissociation pressure of TiH. was 2 x lO-3 torr at room temperature. The F.C.T/F.C.C. transition of the high composition hydride was investigated within the temperature range 20-75°C and the transition temperature of Til2 was deduced as 110°C. The correlation and variation of ? and R are explained qualitatively from features of the conduction band and crystal structures. The chemical boundaries of titanium- hydrogen alloy are deduced, and a phenomenological model is proposed to account for the electronic nature of titanium hydride. The experimental results are compared with the predictions of the theoretical models available and general agreement is observed. The interaction of oxygen with titanium films gave a maximum increase of ? 1.2eV and a large increase of R (> 20%) and an equilibrium pressure P ~ 10-4 torr. When P was raised above 10-4 torr R increased slowly but ? decreased by 0.5-0.8eV. An explanation for these changes of d > and R is given which is consistent with the different chemical phases of Ti-O alloy, and a mechanism is proposed for the diffusion of oxygen atoms into the titanium lattice. The interaction of water vapour reduced ? by 950meV and increased the R by ~ 10-20% at an equilibrium pressure P ~ 10-2 torr. Above this pressure the resistance increased slowly but ? increased by 500-600meV. An explanation is given in terms of dissociative chemisorption of water molecules, solution of oxygen atoms in the titanium lattice, and the formation of an hydroxyl complex at the surface. The work function of 60 clean titanium films was distributed in the range from 4.0eV to 5.3eV; the nature of this distribution is discussed.
Supervisor: Surplice, N. A. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.778963  DOI: Not available
Keywords: QC Physics
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