The vacuum-annealed undoped polycrystalline CVD diamond electrodes: the impedance-spectroscopy and photoelectrochemical studies

The electrochemical impedance, photocurrent, and photopotential are measured in the supporting electrolyte solution (2.5 M H 2SO 4) for electrodes made of the undoped polycrystalline CVD diamond films annealed in vacuum at 1500–1640 °C. Analysis of the impedance spectra allowed concluding that both...

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Bibliographic Details
Published in:Electrochimica acta 2005-01, Vol.50 (5), p.1149-1156
Main Authors: Pleskov, Yu.V., Krotova, M.D., Elkin, V.V., Ralchenko, V.G., Khomich, A.V., Khmelnitskiy, R.A.
Format: Article
Language:English
Subjects:
Diamond
Dislocations
Electrochemical impedance
High-temperature annealing
Photoelectrochemistry
Photopotential
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Summary:The electrochemical impedance, photocurrent, and photopotential are measured in the supporting electrolyte solution (2.5 M H 2SO 4) for electrodes made of the undoped polycrystalline CVD diamond films annealed in vacuum at 1500–1640 °C. Analysis of the impedance spectra allowed concluding that both the amount of a nondiamond conducting phase in the electrode bulk and its conductivity increased upon annealing. With increasing annealing temperature, the photopotential passed through a maximum at ∼1570 °C. The photosensitivity of “metal-like” samples (annealed at temperatures ≥1630 °C) is negligibly small. Judging from the sign of the photopotential (positive) and photocurrent (cathodic), the studied material formally behaves as a p-type semiconductor. It is suggested that the photoeffects are caused by the structure defects, in particular, dislocations in diamond crystallites, formed close to intercrystalline boundaries during the high-temperature annealing.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2004.08.012